PCB components and there function! By Imran

In its simplest form, a PCB is a plastic board reinforced with glass. Attached to this board are copper lines and pads which connect together, cut from a copper layer. These copper lines (known as traces) allow electrical charge to flow through the PCB, providing power to the different components that are situated systematically on the board. The copper traces function in the place of wires, guiding the electricity to the correct destination.

The Layers of a The simplest PCBs are single sided boards (one copper layer). However, the copper traces can also be installed on both sides of the board, creating a double sided PCB. They become more and more complex as additional layers are added to the original design. These new layers have their own copper trace formations. The copper connections cannot cross one another without the path of the electrical charge being compromised, so multi layered PCBs become necessary for advanced electronics. However, in the single sided boards one side is reserved for the copper trace and the other side houses the components. On top of the copper layer sits the solder mask and the silkscreen. The solder mask is what makes the PCB its recognisable green colour. This has the function of insulating the copper from any metal parts that might accidently come into contact with it. However, parts of the metal will remain exposed so that they can be soldered to. The silkscreen sits on top of the solder mask again. This has letters and numbers drawn on it which make the assembly of the PCB easier for the engineer (or the hobbyist!). The Components circuit board If the copper traces behave like the skeleton of the PCB, acting as its basic structure – then the components are the vital organs. Each one has a different function. They give the circuit the unique qualities that make it fit for its intended purpose. Depending on the device or electronic item a PCB is designed for, different components will be needed for different circuits. These components can consist of a wide range of electronic parts. Some common PCB components include: Battery: provides the voltage to the circuit. Resistors: control the electric current as it passes through them. They’re colour coded to determine their value. LEDs: light emitting diode. Lights up when current flows through it, and will only allow current to flow in one direction. Transistor: amplifies charge. Capacitators: these are components which can harbour electrical charge. Inductor: stores charge and stops and change in current. Diode: allows current to pass in one direction only, blocking the other. Switches: can either allow current or block depending if they are closed or open.

Fluidized-Bed Heat Exchangers! By Imran

Fluidized-Bed Heat Exchangers.

In a fluidized-bed heat exchanger, one side of a two-fluid exchanger is immersed in a bed of finely divided solid material, such as a tube bundle immersed in a bed of sand or coal particles, as shown in Fig. 1.3. If the upward fluid velocity on the bed side is low, the solid particles will remain fixed in position in the bed and the fluid will flow through the interstices of the bed. If the upward fluid velocity is high, the solid particles will be carried away with the fluid. At a ‘‘proper’’ value of the fluid velocity, the upward drag force is slightly higher than the weight of the bed particles. As a result, the solid particles will float with an increase in bed volume, and the bed behaves as a liquid. This characteristic of the bed is referred to as a fluidized condition. Under this condition, the fluid pressure drop through the bed remains almost constant, independent of the flow rate, and a strong mixing of the solid particles occurs. This results in a uniform temperature for the total bed (gas and par- ticles) with an apparent thermal conductivity of the solid particles as infinity. Very high heat transfer coefficients are achieved on the fluidized side compared to particle-free or dilute-phase particle gas flows. Chemical reaction is common on the fluidized side in many process applications, and combustion takes place in coal combustion fluidized beds. The common applications of the fluidized-bed heat exchanger are drying, mixing, adsorption, reactor engineering, coal combustion, and waste heat recovery

Physical Properties of Refrigerants R-417A Environmental Classification HFC! By Imran

Physical Properties of Refrigerants R-417A Environmental Classification HFC

Molecular Weight 106.8 Bubble Point (1 atm, ºC) -39.1 Critical Pressure (bar-abs) 40.4 Critical Temperature (ºC) 87.1 Critical Density (Kg/m^3) 520.6 Liquid Density (25 ºC, Kg/m^3) 1151.3 Vapor Density (bp,Kg/m^3) 5.681 Heat of Vaporization (bp, KJ/Kg) 200.75 Ozone Depletion Potential (CFC 11 = 1.0) 0 Global Warming Potential (CO2 = 1.0) 1950 ASHRAE Standard 34 Safety Rating A1 Temperature Glide (ºC) 5.5 Composition: A blend of HFC refrigerants R-125, R-134A and hydrocarbon R-600 (butane) (46.6 / 50 / 3.4 wt%) Application: An alternative to R-22 in medium temperature refrigeration and air conditioning. Performance: Both suction and discharge pressures will run lower than R-22, which may affect valve operation or orifice tube selection. Loss of capacity may be significant at lower evaporator temperatures, but generally not a problem in properly sized equipment at warmer application temperatures. Lubricant: The hydrocarbon component in R-417A helps promote oil return in systems containing mineral oil or alkylbenzene. Although HFC refrigerants won’t mix with these oils, the hydrocarbon addition thins the oil and keeps it moving around the loop. More complicated piping arrangements or large hold-up volumes may still require some oil be changed to POE. R-417A R-417A Available in the following sizes: 26R417ART 12 Kg RETURNABLE CYLINDER 44R417ART 20 Kg RETURNABLE CYLINDER 100R417ART 46 Kg RETURNABLE CYLINDER 1587R417ART 720 Kg RETURNABLE DRUM

Daikin ENVi Thermostat Installation Manual Step! By Imran

Daikin ENVi Thermostat Installation ManualStep

. Position and Wire the DPCA The Daikin Power and Communication Adapter (DPCA) provides an interface between the thermostat and Indoor Unit. To install the DPCA: 1. Position the DPCA in a suitable location, away from water and near the Indoor Unit (for example, a backside cavity of a wall-mounted unit). The DPCA is not plenum rated and should be mounted in a non-plenum space. 2. Connect the DPCA power cable to the Indoor Unit power supply terminals. Ensure that the electrical connections are securely tightened. 3. Remove the DPCA cover by grasping both sides and pulling along the length of the DPCA. 4. Use the Wiring Harness to connect the P2 terminal on the DPCA to the S21 terminal on the Indoor Unit’s main PCB. Refer to the Daikin system installation manual for information about accessing the S21

Step 3. Install the Daikin ENVi Thermostat The ideal location for the thermostat is approximately 5 ft (1.5 m) above floor level in the main living area. Do not install the thermostat: Close to sources of heat such as incandescent lights Near supply heating/cooling sources In direct sunlight On exterior, non-insulated or poorly insulated walls In the kitchen or other areas of potentially high heat and/or humidity In an area that could restrict air flow To install the thermostat:

1. If necessary, remove the previous thermostat. 1. Gently separate the backplate from the Daikin ENVi thermostat. 2. Place the thermostat backplate on the wall. Make sure that any existing wires can be inserted through the opening for the wiring. If the backplate does not adequately cover the area where the previous thermostat was installed, attach the trim plate to the back of the backplate to increase its coverage. 3. Using the backplate as a template, mark the location of the

AHU PRE-FILTER FUNCTIONS! By Imran

PRE-FILTER FUNCTIONS

Pre-filters are a nice feature to have in your air purifier. It also expands the lifetime of HEPA and activated carbon filters which follow after pre-filter. The pre-filter is the front line in an air purifier, and it captures largest particles which the primary filter usually can’t do. Pre-filters come as a very handy feature that strengthens air filtering technology by preventing debris getting into the next, primary filter. Pre-filters usually have a long lifetime because they can be washed, vacuumed and replaced whenever it`s necessary. If your air purifier is running all the time, then it`s recommended to clean the pre-filter at least one a month. Otherwise, pollution such as fur, pollen, dust and hair will get stucked in the pre-filter after a while, and it will dramatically decrease the overall performance of an air purifier. Washable filter is a great plus, which will save you a lot of money long term

Eventually, after a longer period, the pre-filter will wear out, after many times of cleaning it, and active air-purifying day after day. So, if you want to keep it safe then buy a new pre-filter and change the old one, when you feel that it is necessary.

Screw compressor! By Imran

Screw compressor By Imran

How does a screw compressor work? Here we will look a bit closer at the screw air compressor technology. What is a screw compressor and what is its basic working principle? The screw element was first developed in 1930s, it has a male and female rotors, the male rotor drives the female rotor if it’s an oil injected screw compressor technology; and a timing gear drive both rotors in the oil free compressor technology as both rotors will run harmonically with minimum calculated clearance between both elements. The basic principle of a screw compressor is as the male and female rotors are rotating in opposite direction they draw air in between them. As the air progresses along the rotors the air is compressed as the volume space between the rotors decreases, hence creating compressed air that is displace to the outlet. The speed of the rotors is optimised at a certain level to minimise mechanical loses (due to heat at very high speed) and volumetric losses (air losses due to very low speed). Unlike a piston compressor a screw compressor generally doesn’t have valves and has no mechanical force that causes unbalance, this means that it can work at a high speed combined with large flow rates and still be contained within a small exterior. A good example of a screw compressor that can produce large volumes of compressed air and with a small footprint is Atlas Copco’s

Scroll Compressor! By Imran

SCROLL COMPRESSOR A scroll compressor is a specially designed compressor that works in a circular motion, as opposed to up-and-down piston action.

Scroll compressors are becoming more popular for use in HVAC systems, as they are more reliable and efficient than reciprocating types. A scroll compressor has one fixed scroll which remains stationary and another moving or orbiting scroll that rotates through the use of a swing link. When this happens, the pockets of refrigerant between the two scrolls are slowly pushed to the center of the two scrolls, causing the reduction of the volume of the gas. It is then discharged though the center port to the condenser. The advantage of a scroll compressor is that it has fewer moving parts and less torque variation compared to the reciprocating compressor. This advantage is translated to a smooth and quiet operation. The scroll compressor is also known as scroll pump or scroll vacuum pump. Scroll compressors can be applied in several different ways to meet a homeowner’s needs for efficiency, comfort, and affordability. Single-stage compressors are found in most home cooling and heating systems. The simplest and least expensive type, they operate at only one speed. Single-stage units can cool or heat a home efficiently. Two-stage compressors operate at two different speeds, more closely matching their cooling or heating output to the exact needs of the home. The ability to run at a lower, more efficient speed helps remove excess humidity from the air while saving energy and the compressor can switch to its full capacity if needed to hold temperatures steady. Two-stage systems are typically more energy-efficient than single-stage systems

CALCULATING RELATIVE HUMIDITY ! By Imran

CALCULATING RELATIVE HUMIDITY By Mohammad Imran

Calculating the RH requires the correct equation(s). The RH is the amount of moisture in the air (via moisture mass or vapor pressure) divided by the maximum amount of moisture that could exist in the air at a specific temperature (via max moisture mass or saturation vapor pressure). RH is expressed as a percentage and has no units since the units in both the numerator and denominator are the same. The percentage is found by multiplying the ratio by 100%. The RH is NOT the dewpoint divided by the temperature. For example, if the temperature was 60 F and the dewpoint was 30 F, you would not simply take (30/60)*100% = 50% RH. Method #1 When given temperature and dewpoint, the vapor pressure (plugging Td in place of T into Clausius-Clapeyron equation) and the saturation vapor pressure (plugging T into Clausius-Clapeyron equation) can be determined. The RH = E/Es*100%. Clausius-Clapeyron equation LN(Es/6.11) = (L/Rv )(1/273 - 1/T) Es = Saturation vapor pressure L = Latent heat of vaporization = 2.453 × 10^6 J/kg Rv = Gas constant for moist air = 461 J/kg T = Temperature in Kelvins Method #2 The mixing ratio is defined as the mass of water vapor divided by the mass of dry air. In a lab setting, the lab technician could measure both the mass of water vapor and mass of dry air in an air sample. The mass of water vapor in a sample of air divided by the mass of dry air is W. The lab technician could then saturated the air (making sure temperature remains the same) and recalculate the mass of water vapor divided by the mass of dry air. This would be Ws. The RH = W/Ws*100% To get W and Ws, use the equation: W= (0.622*e) / (P - e) and Ws = (0.622*Es) / (P - Es) This requires that E and Es are known. Therefore, without using the Clausius-Clapeyron equation, calculating RH outside of a lab setting is difficult. --operational methods of calculating RH-- 1. Mixing ratio can be determined using the Skew-T log-P diagram. For any pressure level, the mixing ratio is read through the dewpoint and the saturation mixing ratio is read through the temperature. By reading the mixing ratio values off the Skew-T you can determine W and Ws for any temperature and dewpoint. RH = W/Ws*100% 2. Take the temperature and dewpoint and plug them into the Clausius-Clapeyron equation. There are computer programs that will do this. The computer uses the graph of the Clausius-Clapeyron equation for all temperature and dewpoints to find RH. 3. Many textbooks have a graph or table data of saturation mixing ratio and/or saturation vapor pressure for various temperatures. Using dewpoint will either give the actual vapor pressure or actual mixing ratio while using temperature will either give the saturation vapor pressure and saturation mixing ratio (depending on if graph is showing vapor pressure or mixing ratio). RH is E/Es*100% or W/Ws*100%.

Symptoms of brain fever 90 plus child death in Bihar due to brain fever

Symptoms of brain fever:

1. Pain in the heart 2. Feeling weak in the muscles 3. Haemiparesis - Feeling weakness in all outer organs of the body, nausea or vomiting 4. Gradient, back and shoulder stiffness 5. On cerebral fever The person also changes in mental condition as well as a high fever and cold. Due to brain fever: 1. In a cerebral fever, people are suffering from brain fever like various viruses such as Rabbis virus, Herpes simplex polio virus, measles virus, and smallpox virus. Also Read - International Yoga Day 2019: PM Modi told, how to learn the benefits of Shalabhasan, how to know 2. Some people have swelling in the brain when a fever is fever. And this swelling occurs from the infection of any lethal virus. Fatal viruses such as Japanese encephalitis virus, St. Lucie Virus, West Nile virus, etc. are the major causes of viral encephalitis 3. Bacterial encephalitis is caused by a very fatal infection. Encephalitis is mainly of two types of primary encephalitis and secondary encephalitis

134A pressure chat! by Imran

410A Pressure Chart ! By Imran

Failure causes of thermostatic expansion valve TXV ! By Imran

thermostatic expansion valve or TXV — can cause a number of symptoms in a system. Here are the ways a TXV can become restricted:

Wax buildup in the valve because the wrong oil was used in the system; Sludge from the byproducts of a compressor burnout; Partial TXV orifice freeze-up from excessive moisture in the system; Foreign material in the orifice; Oil-logged TXV from refrigerant flooding the compressor; Too much oil in the system; TXV is adjusted too far closed; Manufacturer’s defect in the valve; or Plugged inlet screen on TXV https://www.youtube.com/channel/UCej-mX5F6GqsPlhhHrQC4Nw

Cause and Troubleshooting an Overheating Compressor ! By Imran

Troubleshooting an Overheating Compressor

Here are a few tips you can try to find the issue before contacting a professional: High head pressure can be caused by dirty condenser coils, a faulty condenser fan, too much refrigerant or perhaps some other heat source near the compressor such as a dryer vent. An electrical problem outside of the A/C also may cause a compressor to overheat, such as voltage issues or spikes in power. This may be a problem with your home's electrical system or something external such as electrical transformer or grid issues. An issue called "high superheat" can be caused by not enough refrigerant in the system, a kink or restriction in the refrigerant line, a malfunctioning metering component or a hot-liquid line too close to the compressor, such as a hot-water pipe. If the compressor is short-cycling, this also can cause overheating. The problem might be due to a dirty air filter or evaporator coil, or a faulty capacitor or metering device

SCROLL COMPRESSOR ! By Imran

A scroll compressor is a specially designed compressor that works in a circular motion, as opposed to up-and-down piston action.

Scroll compressors are becoming more popular for use in HVAC systems, as they are more reliable and efficient than reciprocating types. A scroll compressor has one fixed scroll which remains stationary and another moving or orbiting scroll that rotates through the use of a swing link. When this happens, the pockets of refrigerant between the two scrolls are slowly pushed to the center of the two scrolls, causing the reduction of the volume of the gas. It is then discharged though the center port to the condenser. The advantage of a scroll compressor is that it has fewer moving parts and less torque variation compared to the reciprocating compressor. This advantage is translated to a smooth and quiet operation. The scroll compressor is also known as scroll pump or scroll vacuum pump. Scroll compressors can be applied in several different ways to meet a homeowner’s needs for efficiency, comfort, and affordability. Single-stage compressors are found in most home cooling and heating systems. The simplest and least expensive type, they operate at only one speed. Single-stage units can cool or heat a home efficiently. Two-stage compressors operate at two different speeds, more closely matching their cooling or heating output to the exact needs of the home. The ability to run at a lower, more efficient speed helps remove excess humidity from the air while saving energy and the compressor can switch to its full capacity if needed to hold temperatures steady. Two-stage systems are typically more energy-efficient than single-stage systems. Variable-capacity compressors provide exceptional control of home temperatures and humidity, because instead of operating at one or two settings, they can modulate their capacity in very small increments throughout a wide operating range. This allows for very precise control of cooling and heating, keeping temperatures even throughout the home and saving energy in the process. While variable-capacity systems tend to be more expensive, they provide exceptional savings on monthly energy bills and can be up to twice as efficient as single-stage models.

Difference Between Star and Delta Connection ! By Imran

Difference Between Star and Delta Connection are as

The terminals of the three branches are connected to a common point. The network formed is known as Star Connection. The three branches of the network are connected in such a way that it forms a closed loop known as Delta Connection. In a star connection, the starting and the finishing point ends of the three coils are connected together to a common point known as the neutral point. But in Delta connection, there is no neutral point. The end of each coil is connected to the starting point of the other coil that means the opposite terminals of the coils are connected together. In Star connection, the line current is equal to the Phase current, whereas in Delta Connection the line current is equal to root three times of the Phase Current. In Star connection, line voltage is equal to root three times of the Phase Voltage, whereas in Delta Connection line voltage is equal to the Phase voltage. The Speed of the star connected motors is slow as they receive 1/√3 of the voltage but the Speed of the delta connected motors is high because each phase gets the total of the line voltage. In Star Connection, Phase voltage is low as 1/√3 times of the line voltage, whereas in Delta Connection Phase voltage is equal to the line voltage. Star Connections are mainly required for the Power Transmission Network for longer distances, whereas in Delta connection mainly in Distribution networks and is used for shorter distances. In Star Connection, each winding receives 230 volts and in Delta Connection, each winding receives 415 volts. Both 3 phase 4 wire and 3 phase 3 wire system can be derived in the star connection, whereas in Delta Connection only 3 phase 4 wire system can be derived. The amount of Insulation required in Star Connection is low and in Delta Connection high insulation level is required.

PCB fault recognise ! By Imran

Chemical fluid leakage How To Recognise Five of the Most Common PCB FailuresThe presence of any chemical fluid that has leaked from a component can seriously damage the PCB and cause failure. Most chemicals are removed in the manufacturing process, but often trace elements are left behind. Inside the packaging of a component, leaks can happen, which cause rapid aging of the semiconductor or package. This chemical leakage can eventually cause shorts or become corrosive.

Issues with the soldering process Solders are the part that provides the necessary means of contact between the component and the circuit, without it the PCB would not work. There are a few solder issues that can cause failure, but the most common are flux contamination and poor processing conditions. Some flux residues can absorb moisture which can become conductive, causing short circuits. If the solder process is not properly set up and controlled, it can lead to open joints and contaminated solder Component barrier breakage The barrier of a component is there to protect the component from the outside environment and also to give a way for the component to connect to the circuit. If this barrier is broken, then the component will become exposed to environmental factors such as oxygen and humidity, which can cause the component to age and then fail. Physical problems with materials The materials used in a PCB can often encounter problems that will cause the board to fail. During the manufacturing stages, if a layer of the PCB is misaligned it will cause short circuits, open circuits and crossed signal lines. If there are psychical defects with the materials such as fractures, voids and delaminations they will seriously affect the performance of the PCB. Failure can also happen if the materials used are impure

Symptoms of Heat stress ! By Imran

The most common signs and symptoms of heat exhaustion include: Confusion Dark-colored urine (a sign of dehydration) Dizziness Fainting Fatigue Headache Muscle or abdominal cramps Nausea, vomiting, or diarrhea Pale skin Profuse sweating Rapid heartbeat Treatment for Heat Exhaustion If you, or anyone else, has symptoms of heat exhaustion, it's essential to immediately get out of the heat and rest, preferably in an air-conditioned room. If you can't get inside, try to find the nearest cool and shady place. Mohammad Imran (HVAC Engineer)

Heat load Calculation in very easy steps/By Imran

For an air conditioner to cool a room or building its output must be greater than the heat gain. It is important before purchasing an air conditioner that a heat load calculation is performed to ensure it is big enough for the intended application. Heat load calculations There are several different methods of calculating the heat load for a given area: Quick calculation for offices For offices with average insulation and lighting, 2/3 occupants and 3/4 personal computers and a photocopier, the following calculations will suffice: Heat load (BTU) = Length (ft.) x Width (ft.) x Height (ft.) x 4 Heat load (BTU) = Length (m) x Width (m) x Height (m) x 141 For every additional occupant add 500 BTU. If there are any additional significant sources of heat, for instance floor to ceiling south facing windows, or equipment that produces lots of heat, the above method will underestimate the heat load. In which case the following method should be used instead. A more accurate heat load calculation for any type of room or building The heat gain of a room or building depends on: The size of the area being cooled The size and position of windows, and whether they have shading The number of occupants Heat generated by equipment and machinery Heat generated by lighting By calculating the heat gain from each individual item and adding them together, an accurate heat load figure can be determined. Step One Calculate the area in square feet of the space to be cooled, and multiply by 31.25 Area BTU = length (ft.) x width (ft.) x 31.25 Step Two Calculate the heat gain through the windows. If the windows don’t have shading multiply the result by 1.4 North window BTU = Area of North facing windows (m. sq.) x 164 If no shading, North window BTU = North window BTU x 1.4 South window BTU = Area of South facing windows (m. sq.) x 868 If no shading, South window BTU = South window BTU x 1.4 Add the results together. Total window BTU = North window + South window Step Three Calculate the heat generated by occupants, allow 600 BTU per person. Occupant BTU = number of people x 600 Step Four Calculate the heat generated by each item of machinery - copiers, computers, ovens etc. Find the power in watts for each item, add them together and multiply by 3.4 Equipment BTU = total equipment watts x 3.4 Step Five Calculate the heat generated by lighting. Find the total wattage for all lighting and multiply by 4.25 Lighting BTU = total lighting watts x 4.25 Step Six Add the above together to find the total heat load. Total heat load BTU = Area BTU + Total Window BTU + Occupant BTU + Equipment BTU + Lighting BTU Step Seven Divide the heat load by the cooling capacity of the air conditioning unit in BTU, to determine how many air conditioners are needed. Number of a/c units required = Total heat load BTU / Cooling capacity BTU --------------------------------------------- MOHAMMAD IMRAN (HVAC Engineer)

HVAC top 35 questions likely to asked in interview

1.Question 1. What Is Local Comfort Cooling System? Answer : They may be integrated, with heating, ventilation and air conditioning provided by a single system, for example, air handling units connected to ductwork, or they may be a combination of separate systems, for example mechanical ventilation but with radiators for heating and local comfort cooling units. 2.Question 2. What Is Centralised Air System? Answer : The most common central cooling system is a split system, which includes an outdoor cabinet containing a condenser coil and compressor, and an indoor evaporator coil, usually installed in conjunction with your furnace. or air handler . The compressor pumps a chemical called refrigerant through the system. 3.Question 3. What Is Constant Volume System? Answer : Constant Air Volume (CAV) is a type of heating, ventilating, and air-conditioning (HVAC) system. In a simple CAV system, the supply air flow rate is constant, but the supply air temperature is varied to meet the thermal loads of a space. Most CAV systems are small, and serve a single thermal zone. 4.Question 4. What Is Variable Air Volume System & Dual Duct System? Answer : Variable Air Volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system. Unlike constant air volume (CAV) systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant temperature. 5.Question 5. What Is Hydronic System Or Air-water System? Answer : Hydronic systems circulate hot water through warming baseboards, radiators and/or radiant tubing in your floors or ceilings. There are many advantages to heating your home using a hydronic system, whether it is for a new home or as a replacement heating system. 6.Question 6. How Vapour Compression Cycle Works ? Answer : The Vapor-Compression Refrigeration Cycle is comprised of four steps. ... The condenser is in contact with the hot reservoir of the refrigeration system. (The gas releases heat into the hot reservoir because of the external work added to the gas.) The refrigerant leaves as a high pressure liquid. 7.Question 7. What Is Vapor Compression Cycle? Answer : Vapor-Compression Refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air-conditioning of buildings and automobiles. 8.Question 8. Why Is A Compressor Used In Refrigeration? Answer : The compressor does exactly as its name says: it compresses the refrigerant. The compressor receives low pressure gas from the evaporator and converts it to high pressure gas. As mentioned earlier, as the gas is compressed, the temperature rises. The hot refrigerant gas then flows to the condenser. 9.Question 9. What Is Auto Refrigeration? Answer : Auto-refrigeration is a process where an unintentional and/or uncontrolled phase change of a hydrocarbon from a liquid state to a vapor occurs, resulting in a very rapid chilling (refrigeration) of the liquid containing local equipment and/or piping. 10.Question 10. How Does A Refrigerant Compressor Work? Answer : oThe compressor constricts the refrigerant vapor, raising its pressure, and pushes it into the coils on the outside of the refrigerator. o When the hot gas in the coils meets the cooler air temperature of the kitchen, it becomes a liquid. oThe refrigerant absorbs the heat inside the fridge, cooling down the air. 11.Question 11. Why Capacity Of Air Conditioner Is Measured In Tons? Answer : A 4 ton air conditioner is one that can remove 48,000 BTUs of heat per hour from the house. For most people, though, 4 tons means 8000 pounds. (A BTU is a British Thermal Unit, approximately the amount of heat you get from burning one kitchen match all the way down.) 12.Question 12. What Is The Meaning Of 1 Ton Of Ac? Answer : A ton, as used in the HVAC field, is a term that describes how much heat the AC unit can remove from a home in one hour. The measurement for heat is the British thermal unit (BTU). One ton of air conditioning can remove 12,000 BTUs of air per hour. 13.Question 13. What Is An Air Conditioning Ton? Answer : A ton is the cooling capacity of an air conditioning system. One ton is equal to the amount of heat required (288,000 Btu) to melt one ton of ice in a 24-hour period. A one-ton air conditioner is rated at 12,000 Btu per hour (288,000/24). A two-ton unit would be rated at 24,000 Btu per hour. 14.Question 14. What Is Btu? Answer : The British thermal unit (Btu or BTU) is a traditional unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. ... Heat is now known to be equivalent to energy, for which the metric unit is the joule; one BTU is about 1055 joules. 15.Question 15. What Is The Meaning Of Btu In Air Conditioners? Answer : Btu – British Thermal Unit (Btu) is the international measure of energy. A Btu is the amount of heat needed to raise 1 (one) pound of water by 1(one) degree Fahrenheit. In HVAC industry, Btu's measure the quantity of heat a conditioning unit can remove from a room per hours. One BTU per hour is equal to 0293 watts. 16.Question 16. What Is Cfm & Infiltration? Answer : The infiltration rate is the volumetric flow rate of outside air into a building, typically in cubic feet per minute (CFM) or liters per second (LPS). The air exchange rate, (I), is the number of interior volume air changes that occur per hour, and has units of 1/h. 17.Question 17. What Is The Hvac System? Answer : While the Energy Center usually tries to avoid the use of acronyms, HVAC is in common use in the heating and cooling industry. It stands for "heating, ventilation and air conditioning," three functions often combined into one system in today's modern homes and buildings. 18.Question 18. What Does A Hvac Engineer Do? Answer : An HVAC engineer's job duties can include the design, installation, maintenance, and repair of heating, ventilation, air conditioning, cooling, and refrigeration systems. 19.Question 19. What Is Psychometry? Answer : Psychometry is a psychic ability in which a person can sense or "read" the history of an object by touching it. Such a person can receive impressions from an object by holding it in his/her hands or, perhaps, touching it to the forehead. 20.Question 20. What Are The Types Of Air Conditioning Systems? Answer : Types of Air Conditioning Systems The choice of which air conditioner system to use depends upon a number of factors including how large the area is to be cooled, the total heat generated inside the enclosed area, etc. o Window Air Conditioner. o Split Air Conditioner. o Packaged Air Conditioner. o Central Air Conditioning System. 21. Question 21. How The Lighting Load Is Calculated? Answer : The standard method consists of three calculation steps: General lighting VA load. When calculating branch circuits and feeder/service loads for dwellings, include a minimum 3VA per sq ft for general lighting and general-use receptacles [220.12]. When determining the area, use the outside dimensions of the dwelling. 22.Question 22. What Is The Function Of Ahu? Answer : An Air Handling Unit (AHU) is used to re-condition and circulate air as part of a heating, ventilating and air-conditioning system. The basic function of the AHU is take in outside air, re-condition it and supply it as fresh air to a building. 23.Question 23. How Does The Ahu Work? Answer : An air handler is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through the building and returns it to the AHU. 24.Question 24. What Is The Purpose Of Air Handling Units? Answer : An air handler, or air handling unit (often called an AHU), is used to condition and circulate air as part of an HVAC system. An air handler usually contains a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. 25.Question 25. Where The Fcu’s Are Used? Answer : A fan coil unit is a simple device consisting of a heating or cooling coil and fan. It is part of an HVAC system found in residential, commercial, and buildings. Typically a fan coil unit is not connected to ductwork and is used to control the temperature in the space where it is installed, or serve multiple spaces. 26.Question 26. What Is The Fcu? Answer : A Fan Coil Unit (FCU) is a simple device consisting of a heating and/or cooling heat exchanger or 'coil' and fan. It is part of an HVAC system found in residential, commercial, and industrial buildings. 27.Question 27. What Is The Meaning Of Fahu? Answer : FAHU is the abbreviation used for FRESH AIR HANDLING UNIT. These are usually centralized units employed to induce fresh air quantities to the confines spaces. They come into picture wherever there are limitations to fresh air intake either directly or through AHUs. 28.Question 28. What Is An Air Conditioner Condenser? Answer : The AC condenser is a very important component found on virtually all modern automotive AC systems. Its primary function is to convert the refrigerant coming from the compressor from a high temperature, high pressure vapor into a high pressure liquid through condensation. 29.Question 29. how Does A Condenser In A Refrigerator Work? Answer : In the refrigeration cycle, there are five basic components: fluid refrigerant; a compressor, which controls the flow of refrigerant; the condenser coils (on the outside of the fridge); the evaporator coils (on the inside of the fridge); and something called an expansion device. 30.Question 30. What Is The Main Function Of A Condenser? Answer : In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, by cooling it. In so doing, the latent heat is given up by the substance, and will transfer to the condenser coolant. 31.Question 31. How Does A Condensing Unit Work? Answer : Inside the condenser, the refrigerant vapor is compressed and forced through a heat exchange coil, condensing it into a liquid and rejecting the heat previously absorbed from the cool indoor area. The condenser's heat exchanger is generally cooled by a fan blowing outside air through it. 32.Question 32. What Are The Types Of Condensers? Answer : The three main types of condensers used in general refrigeration systems are: o air-cooled. o water-cooled. o evaporative. 33. Question 33. What Is A Rotary Air Compressor? Answer : A rotary-screw compressor is a type of gas compressor that uses a rotary-type positive-displacement mechanism. They are commonly used to replace piston compressors where large volumes of high-pressure air are needed, either for large industrial applications or to operate high-power air tools such as jackhammers. 34.Question 34. What Is A Gas Compressor Used For? Answer : A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. 35.Question 35. What Is The Use Of Compressor In Refrigeration? Answer : The compressor does exactly as its name says: it compresses the refrigerant. The compressor receives low pressure gas from the evaporator and converts it to high pressure gas. As mentioned earlier, as the gas is compressed, the temperature rises. The hot refrigerant gas then flows to the condenser.------------- Mohammad Imran HVAC Engineer

Types of hazards

Some items are hazardous by nature, while others only become hazardous if used inappropriately or carelessly. Often, accidents don’t just happen – they are a result of workers neglecting or ignoring hazardous situations. There are two basic categories of hazard: Acute hazard Acute hazards are those that have an obvious and immediate impact. Chronic hazard Chronic hazards have a more hidden, cumulative, long-term impact. An example of an acute hazard is a slippery floor where there is an immediate danger of someone slipping and being injured. A chronic hazard could be workplace bullying, where the long-term impact may result in stress or other psychological injury. Hazards generally fall into one of six groups: Physical – Slippery floors, objects in walkways, unsafe or misused machinery, excessive noise, poor lighting, fire. Chemical – Gases, dusts, fumes, vapours and liquids. Ergonomic – poor design of equipment, workstation design, (postural) or workflow, manual handling, repetitive movement. Radiation – Microwaves, infra-red, ultraviolet, lasers, X-rays and gamma rays. Psychological – Shiftwork, workload, dealing with the public, harassment, discrimination, threat of danger, constant low-level noise, stress.

Why oil return in refrigerant

The oil return in refrigeration systems is of key importance for the service life of the compressor and thus for a secure constant supply of refrigeration. In most compressors some lubrication oil is carried along with the compressed refrigerant. In the liquid refrigerant the oil is dissolved in the refrigerant and is transported without problems. In the vaporised refrigerant the oil remains liquid in the lower parts of the system. This can result in lack of oil in the compressor. To return the oil to the compressor, a minimum velocity must be maintained in the pipes. If the velocity in the rising pipe on the intake side of the compressor is too low (partial load), the oil is not returned to the compressor due to its higher density. The velocity in the rising pipe depends on the pipe diameter and the refrigerant mass flow. A small diameter of the rising pipe results in a high velocity and ensures the return of the oil even under partial load. However, at full load the pressure loss increases due to the small diameter. To compensate for this disadvantage, double rising pipes are used. During partial load oil gathers in a bend at the bottom of the double pipe. The oil in the bend blocks one of the two pipes so that the refrigerant flows at high velocity through the other pipe and transports the oil to the compressor. At full load the oil in the bend is pressed upwards so that the refrigerant flows through both pipes. Mohammad Imran HVAC Engineer

Oil Failure Switch

OIL FAILURE SWITCH An oil failure switch is provided with high-speed compressors. This differential pressure switch is designed to prevent operation of the compressor in the event of low oil pressure. The switch has one bellows connected to the discharge oil line of the compressor oil pump and the other connected to the compressor crankcase suction refrigeration pressure. The switch is set to open the electrical circuit and to stop the compressor when the oil pressure drops to a low-pressure set point. The switch closes the electrical circuit and starts the compressor when the oil pressure reaches the reset set point. To start the compressor after it has been stopped and the contacts of the oil failure switch have opened, a time delay mechanism works in conjunction with the compressor motor controller. The time delay switch should open 10 to 30 seconds after the compressor motor has started. The oil pressure will normally build up within this time interval. The oil pressure switch will have made contact to keep the compressor motor electrical circuit energized after the time delay switch opens. If the oil pressure has not built up within about 30 seconds after the compressor is started, the contacts of the oil pressure differential switch will not have closed. The compressor will stop because the time delay relay switch is open MOHAMMAD IMRAN HVAC ENGINEER

High pressure cutout switch

HIGH-PRESSURE CUTOUT SWITCH A high-pressure cutout switch is connected to the compressor discharge line to protect the high-pressure side of the system against excessive pressure. The design of this switch is essentially the same as that of the low-pressure cutout switch. However, the low-pressure cutout switch is made to CLOSE when the suction pressure reaches its upper normal limit. The high-pressure cutout switch is made to OPEN when the discharge pressure is too high. As mentioned before, the low-pressure cutout switch is the compressor control for normal operation of the plant. The high-pressure cutout switch, on the other hand, is a safety device only and does not have control of compressor operation under normal conditions. ----------------------------------------------------------------------------------- MOHAMMAD IMRAN HVAC ENGINEER

Low pressure cutout switch

LOW-PRESSURE CUTOUT SWITCH The low-pressure cutout switch is also known as a suction pressure control switch. It is the control that causes the compressor to go on or off as required for normal operation of the refrigeration plant. This switch is connected to the suction side of the compressor and is actuated by pressure changes in the suction line. When the solenoid valves in the lines to the various evaporators are closed so that the flow of refrigerant to the evaporators is stopped, the pressure of the vapor in the compressor suction line drops quickly. When the suction pressure has dropped to the set pressure, the low-pressure cutout switch causes the compressor motor to stop. When the temperature in the refrigerated spaces has risen enough to operate one or more of the solenoid valves, refrigerant is again admitted to the cooling coils, and the compressor suction pressure builds up again. At the desired pressure, the low-pressure cutout switch closes, starting the compressor again and repeating the cycle. The oil pressure switch will have made contact to keep the compressor motor. -----------------------×××××××---------------------------------------------------------- MOHAMMAD IMRAN HVAC ENGINEER

Easy way to calculate heat Load

load or heat gain A building or room gains heat from many sources. Inside occupants, computers, copiers, machinery, and lighting all produce heat. Warm air from outside enters through open doors and windows, or as ‘leakage’ though the structure. However the biggest source of heat is solar radiation from the sun, beating down on the roof and walls, and pouring through the windows, heating internal surfaces. The sum of all these heat sources is know as theheat gain (or heat load) of the building, and is expressed either in BTU (British Thermal Units) orKw (Kilowatts). For an air conditioner to cool a room or building its output must be greater than the heat gain. It is important before purchasing an air conditioner that a heat load calculation is performed to ensure it is big enough for the intended application. Heat load calculations There are several different methods of calculating the heat load for a given area: Quick calculation for offices For offices with average insulation and lighting, 2/3 occupants and 3/4 personal computers and a photocopier, the following calculations will suffice: Heat load (BTU) = Length (ft.) x Width (ft.) x Height (ft.) x 4 Heat load (BTU) = Length (m) x Width (m) x Height (m) x 141 For every additional occupant add 500 BTU. If there are any additional significant sources of heat, for instance floor to ceiling south facing windows, or equipment that produces lots of heat, the above method will underestimate the heat load. In which case the following method should be used instead. A more accurate heat load calculation for any type of room or building The heat gain of a room or building depends on: The size of the area being cooled The size and position of windows, and whether they have shading The number of occupants Heat generated by equipment and machinery Heat generated by lighting By calculating the heat gain from each individual item and adding them together, an accurate heat load figure can be determined. Step One Calculate the area in square feet of the space to be cooled, and multiply by 31.25 Area BTU = length (ft.) x width (ft.) x 31.25 Step Two Calculate the heat gain through the windows. If the windows don’t have shading multiply the result by 1.4 North window BTU = Area of North facing windows (m. sq.) x 164 If no shading, North window BTU = North window BTU x 1.4 South window BTU = Area of South facing windows (m. sq.) x 868 If no shading, South window BTU = South window BTU x 1.4 Add the results together. Total window BTU = North window + South window Step Three Calculate the heat generated by occupants, allow 600 BTU per person. Occupant BTU = number of people x 600 Step Four Calculate the heat generated by each item of machinery - copiers, computers, ovens etc. Find the power in watts for each item, add them together and multiply by 3.4 Equipment BTU = total equipment watts x 3.4 Step Five Calculate the heat generated by lighting. Find the total wattage for all lighting and multiply by 4.25 Lighting BTU = total lighting watts x 4.25 Step Six Add the above together to find the total heat load. Total heat load BTU = Area BTU + Total Window BTU + Occupant BTU + Equipment BTU + Lighting BTU Step Seven Divide the heat load by the cooling capacity of the air conditioning unit in BTU, to determine how many air conditioners are needed. Number of a/c units required = Total heat load BTU / Cooling capacity BTU ------------------------------ Mohammad Imran HVAC Engineer imranjmi786@gmail.com

What is BMS & why we use

A building management system can add significant operating costs savings to your company, while providing security to your property, resources, assets and building occupants. Since 1987, we have been creating BMS systems for companies who want to become more energy efficient and sustainable. Our experts can design and create an intelligent building system for your company that will provide many extraordinary benefits. Here are some examples of how BMS works: A security system can be customized to meet the needs of your property and also address building vulnerabilities. Building occupants and tenants will be pleased to know that your building is being monitored and controlled to maintain maximum security. Your building management system provides access control, surveillance and intrusion detection technologies, RFID scanners, access card readers, biometric scans, digital video surveillance, CCTV, smoke and toxic gas detection devices, lighting control, and much more. How BMS works is that energy usage is reduced and waste is eliminated. System performance is optimized, and you will save your company time and money on repairing system failures by utilizing detection devices. Your equipment operating cost expenditures will decrease by about 15% annually, and new technology will improve the sustainability of systems and equipment. All this equates to more savings and less headaches. A building management system is adaptable to change, and can integrate new equipment as your business needs evolve. New technologies can be added to your existing infrastructure, and access to outside platforms can also be integrated. Another great benefit of a BMS system is that the value of your company and property will increase. This is how BMS works: it provides security to your property, building occupants, and business assets such as IT data and other important resources. A building management system incorporates access control to elevators and other areas inside your building. Your managers will be able to steer, and reduce, transient traffic throughout your building. This is an important safety measure that protects against security breaches. By having a well-managed security system in your building, you will be able to protect your company against employee theft and tampering, and also deter any criminal activity, damage or loss to your property. A BMS lighting system uses a sophisticated web of sensors and occupancy controls. Your managers can automatically shut down lighting during scheduled times of the day or night, or when areas are unoccupied. Lighting management also includes outside walkways, parking garages, loading docks etc. Your company should realize about a 30% annual savings on lighting costs, according to a report by the U.S. Department of Energy. Your building management system also provides indoor environmental safety and comfort through your HVAC system. Air quality and detection of toxic gases are all a part of your BMS system. Smoke detection and containment also work with your HVAC system and provide for circulating smoke outside of your building in the event of a fire. Smokeless containment areas are provided for the protection of building occupants. This is how BMS works to save lives and your property. --------------''''''''''------------ MOHAMMAD IMRAN HVAC ENGINEER imranjmi786@gmail.com

Air Conditioner Won’t Turn Off ,Air Conditioner Won’t Stop Running

If your AC stays on longer than it should, you may have a dirty filter. Clean or replace your filter to see if that remedies the situation. If your system is older or improperly sized, it also can cause the system to work too hard, cycle too often, and have difficulty shutting off. Other problems that may cause your AC to run constantly include: A stuck fan relay A short in the thermostat cable A thermostat that’s gone bad Central Air Conditioner Won’t Turn On If your central air system doesn’t come on, it may be as simple as to adjust the thermostat. If that doesn’t work, call a technician as your HVAC system may need to be repaired or replaced. AC Window Unit Won’t Kick On Similarly, with a window unit, you first should check the temperature setting on the unit and make sure that electrical current is flowing into the system. Again, if neither of those troubleshooting efforts locates the problem, call for professional help for AC window unit repair . AC Fan Not Working AC Fan Not Working Inside If your AC indoor fan isn’t working, first check to make sure a breaker hasn’t been tripped. If all is OK, check your air filter. If it’s blocked, then you may be able to fix it yourself. If there’s ice on the evaporator coil and refrigerant lines, allow the ice to melt, then check again to see if the fan is working. If it isn’t working, that might have caused your coil to freeze. A frozen coil requires a service call, because your technician may need to replace the contacts inside the fan relay, the fan belt, or the even the motor itself. AC Fan Not Working Outside When your AC isn’t cooling properly, you may want to check your outdoor unit. If the outdoor fan isn’t spinning, first check the breaker or fuse box. If a reset doesn’t correct the problem, there may be a couple of problems at work here. Start capacitor not working: If your compressor is still working, your fan’s motor or start capacitor may not be working. You can try to troubleshoot it by pushing the fan with a wooden stick. Don’t do it by hand, since if the fan does start, it could cut your fingers. If it still doesn’t start to spin, you need to call your local technician. Turn your unit off until she or he comes. If you don’t, you risk burning out your compressor—a major repair. Outdoor fan motor stuck: Dirt or rust may have caused the fan to get stuck. If the unit requires more extensive repairs, you may need to repair or replace the outdoor fan motor. Mohammad Imran HVAC Engineer

Use of VAV in HVAC

VAV Air Handlers The air handler blower fan needs to modulate to vary the air flow depending on demand. Typical Variable Air Volume boxes have a flow sensor inside them to measure airflow. The air flow and temperature variables control damper position based on temperature demands and C.F.M. Mohammad Imran HVAC Engineer

Direct Expansion Air Conditioning

Direct Expansion Air Conditioning What It Is A direct expansion air conditioning (DX) system uses a refrigerant vapour expansion/compression (RVEC) cycle to directly cool the supply air to an occupied space. DX systems (both packaged and split) directly cools the air supplied to the building because the evaporator is in direct contact with the supply air, Expansion refers to the treatment of the refrigerant (a valve reduces its pressure and temperature) prior to it entering the evaporator. DX systems can come equipped with all the components in the unit (packaged system) intended for installation on the rooftop or by the side of a building; or it may have some components installed inside the building and some outside (split system). DX systems require a ventilation fan to distribute the cool air and resupply/re-circulate it. How It Works A RVEC cycle has four basic components; an evaporator, compressor, condenser, and thermal expansion control device. The evaporator (located inside the supply air ductwork) absorbs heat through the process of expanding the refrigerant flowing within it. The refrigerant then flows to a compressor which compresses it causing it to condense in the condenser and release the heat it removed from the supply air. The condensed liquid refrigerant then flows through the thermal expansion control device which controls the flow and pressure of the refrigerant back into the evaporator. Packaged Systems – Packaged DX units contain all 4 parts of the RVEC system, as well as fans and internal ducting. These units are designed to be installed easily to serve local zones cooling needs; multiple units can be installed to service multiple zones in a building. Split Systems – These systems generally have the evaporator and fans inside the building, while the rest of the RVEC system components are a separate unit placed outside the building. This allows system designs that are more flexible, allowing performance that can satisfy greater variations on system demands. Split units are made to an incremental performance scale, meaning only certain working load sizes are available. Benefits DX systems are less expensive to install, and uses less space in mechanical and electrical rooms than centralized cooling systems DX systems can be expanded in an incremental fashion to match changing building requirements Packaged Systems have standardized operating performances per unit, allowing more precise system sizing Packaged Systems generally require less ventilation, and do not require dedicated condensate lines Packaged Systems occupy less space than comparable split systems Split Systems tend to be larger allowing for fewer units, and therefore less maintenance costs than a comparable Packaged system Split Systems have lower noise levels because the compressor unit is located further away from the cooling load area Split Systems may allow vertical duct shafts to be smaller in size. ------by------------- Mohammad Imran HVAC Engineer

Chiller descaler

Chiller Descaler Why descale your chiller? Chillers, condensers and even cooling towers require maintenance due to the harsh mineral deposits such as calcium, lime, mud and rust that rob heat transfer efficiency. For instance, most major manufacturers of chiller equipment generally design chillers to operate with a maximum "thermal resistance" or "fouling factor" of 0.0005 inches of buildup. As a result, with only 0.0360 inches (about 1/32'') of deposit corresponds to an increase in energy costs of over 30%! Now ask yourself, "Can I afford not to do a RYDLYME cleaning on the chiller tower"? How to use RYDLYME descaler to descale your equipment: When isolating and cleaning the barrel on a tube chiller or cooling tower, RYDLYME will circulate through the water side and completely dissolve the scale in to a liquid suspension (like sugar in coffee), easily cleaning the hard to reach areas such as tube enhancements. Typically, cleanings can be accomplished in 4-6 hours depending on the severity of scale and volume of the barrel. RYDLYME can even be circulated via cooling tower to eliminate the need to shutdown the system! Preventative maintenance cleanings with RYDLYME will ensure optimal efficiency, bringing approach temperatures and pressures down to "as designed" specifications AND will help extend the life of the equipment. ------------------------ Mohammad Imran HVAC Engineer

Electrical (LOTO ) Lock Out Tag Out

Electrical Safety Lock Out Tag Out (LOTO) What is LOTO? Answer --) Electrical Lock Out Tag Out the physical restraint of all hazardous energy sources that supply power to a piece of equipment, machinery or system. LOTO also includes applying a Warning Tag on the physical restraint device. This documents the Authorized LOTO personnel and the date. LOTO operations must be done on all equipment, machinery or system Shut Downs before Authorized Personnel can perform repairs or service. Most equipment and machinery has an Energy Isolation Device. These devices are usually put into the off position to shut down the hazardous energy source. Physical restraints (Lock Out Devices) can be put onto the Energy Isolation Device and secured with padlocks. Examples of Lock Out Devices include: ball valve and gate valve lock outs, circuit breaker lockouts, plug and wall switch lock outs and pneumatic lock outs. The total shutdown and restraint of all hazardous energy sources including the safe release of stored hazardous energy (e.g. capacitors and pressure in a line) must be accounted for. Does LOTO apply to cord and plug equipment that may be used in the office or a lab? Answer -- Yes and No! NO, if the only energy source that powers the equipment is a cord and plug then the employee needs to remove the plug from the electrical power source and keep the cord and plug under his/her exclusive control while performing the service or maintenance task. Yes, LOTO does apply to cord and plug electrical equipment if there is another energy source (i.e.-a capacitor that stores electrical energy inside of the equipment) that could harm the employee if it was not identified and/or isolated prior to doing a service or maintenance task. Generally, stored electrical energy sources (i.e.-capacitors) are identified with an Electrical Shock Hazard Warning Label. What are hazardous energy sources and types of service and repair activities? Answer -- Some examples of hazardous energy sources include electrical, hydraulic, pneumatic, chemical, thermal or mechanical energy. Hazardous energy can also be stored (e.g. capacitors or gravity equipment, machinery or system components that are suspended, blocked or chocked). Service and repair activities may include but are not limited to: installing, setting up, adjusting, inspecting, lubricating, cleaning, making adjustments or tool changes. If I am responsible for the repairs or services on some equipment or machinery powered by a hazardous energy source, must I follow special requirements? Answer -- Yes! OSHA regulations and the University of Virginia Lock Out Tag Out (LOTO) Policy make LOTO procedures mandatory. Special requirements include the following: Step by step LOTO procedures must be developed, documented and followed for all equipment, machinery or system Shut Downs before Authorized Personnel can perform service or repairs. Authorized Personnel can include faculty, staff or students who are designated and qualified by the department to safely operate equipment, machinery or a system and; perform maintenance such as service and repairs. Authorized Personnel must be initially trained on LOTO procedures prior to performing Shut Downs. Personal padlocks, warning tags and lock out devices must be provided by the department and assigned to Authorized Personnel. Also, personnel affected by LOTO procedures and Shut Downs when working in controlled spaces (e.g. electrical power to work area is secured during renovation, demolition activities or abatement of hazardous materials) must be provided personal padlocks and warning tags. Are there any special precautions to take with equipment hardwired into a disconnect box? Answer -- Yes! If you shut off electrical power by turning off a Disconnect Switch you may be at risk of an unexpected failure of the equipment such as electrical arcing that can produce explosive forces. To avoid electrical risks and potential injuries read the Precautions below. NOTE: Individuals such as faculty, staff and students working in lab and shop environments, must follow these Special Procedures. These procedures will help to prevent injuries in the event there is a mechanical failure in the equipment. Take these precautions to avoid electrical safety risks prior to performing Lock Out Tag Out on "hard wired" equipment in a lab or a shop: Individuals such as faculty, staff and students are not to perform any repairs or service that involves working on energized conductors or; at any time coming into accidental contact with energized conductors that may become exposed if any electrical safety guard, shield or enclosure is removed. This type of work needs to be referred to: a qualified and licensed electrician (i.e. Facilities Management), or an equipment manufacturers' service technician. These individuals are authorized through special training and knowledge to perform work on equipment when it is energized or there is a potential risk of coming into contact with any of the electrical systems that can be energized. Please refer to the University's Electrical Safety policy SEC-029. Individuals in the shop or lab must be qualified (authorized by the department and trained) to perform the intended Lock Out procedure and assure all hazardous energy sources are shut off prior to doing the work. A qualified individual must have documented training and knowledgeable on the: specific hazards inherent in the equipment, the LOTO procedure and applicable LOTO devices to secure the equipment. What are the special procedures to follow when shutting off a disconnect switch? Safe procedures begins with wearing the right level of electrical personal protective equipment (PPE). PPE will help to prevent injuries if an electrical arc event occurs due to a faulty disconnect switch. This occurrence is expected to be minimal but you must be prepared and protected. You will need to wear plastic frame safety glasses (no metal) or impact resistant safety goggles (preferable) to protect your face from any shrapnel. You will also need to use hearing protection to protect your ears from explosive noise. Wear a heavy leather glove on your left hand and a long sleeve 100% cotton shirt or lab coat to protect your skin from burns. Do not wear any synthetic clothing such as rayon or polyester including fleece. These fabrics can exacerbate the level of burn injuries in the event of an electrical arc flash by embedding into the skin. This goes for what you are wearing underneath the long sleeve shirt or lab coat. Donned in your PPE, use the "left hand rule" to operate the disconnect switch into the off position. Twist your face and torso away and use your left hand to turn the safety switch off. This helps to prevent a direct injury to the face, eyes, and front of torso in the case of a sudden mechanical failure inside the disconnect box. Next, operate the power switch of the equipment or machinery to verify the power is off. The electrical disconnect switch must be locked out by the authorized individual shutting off the power as well as any other authorized individual who will perform work on the equipment. Remember! A qualified licensed electrician must perform services or repairs on electrical equipment where there is any risk of coming into contact with energized conductors. Are there resources available to help me develop appropriate LOTO procedures? Answer -- Yes! Equipment manufacturers, their service representatives or; the Equipment Operator’s Manual, can provide information on how to safely isolate the equipment’s energy source(s) during service or maintenance activities. Personnel must be authorized by the Department to perform this task; their qualification should include training and proficiency to perform the task. Do I have to document anything before I shut down equipment or machinery for service and repairs? Answer -- Yes! LOTO procedures must be written down in an easy to understand step by step sequence that accounts for the safe Shut Down of all hazardous energy sources including stored energy. The goal is consistent and safe Shut Downs by all Authorized Personnel. Written LOTO procedures are the foundation of LOTO training. This training must be documented and is required to Authorize and Qualify personnel to perform Shut Downs. Download the LOTO Procedure Form word | pdf Do employees need to be trained before they can shut down and lock out equipment and machinery for repairs? Answer -- Yes! Only Authorized Personnel can Shut Down and lock out equipment powered by hazardous energy sources. Personnel are Authorized and Qualified through training on LOTO regulatory requirements and LOTO procedures for the equipment or machinery they have been assigned to work on. Personnel affected by Shut Downs because they are operators of the equipment/machinery or they must work in a controlled work area must also participate in LOTO training. If I am responsible for several employees doing a Shut Down on equipment/ machinery for some service or repairs, does each employee have to perform LOTO? Answer -- Yes! The regulations refer to this as multiple or "group lock out". Special procedures for "group lock out" must be included in the mandatory LOTO procedure. Special "group lock out" devices are available that can hold multiple padlocks. This assures each person’s safety until the work by all Authorized Personnel has been completed. All personnel participating in a "group lock out" must be trained on the LOTO procedure and the special "group lock out" procedures. Do employees need to wear personal protective equipment during LOTO Operations? Answer -- Most likely yes. Shutting Down electrical energy sources could result in arcs or contact with energized parts. Safety glasses or faceshields to protect from potential electrical arcs or explosions and insulated gloves rated for the voltage are advisable. Only qualified electricians can shut down electrical energy sources. Working around thermal energy sources such as medium and high pressure steam may require clothing and/or thermal blankets to protect from burn hazards. These are only a couple of examples. Contact EHS for assistance on appropriate personal protective equipment for your specific operation. Which OSHA regulations require LOTO? HOISTING EQUIPMENT 29 CFR 1910.179 -- Overhead and Gantry Cranes -- The power supply to the runway conductors of the hoisting mechanisms needs to be controlled by a fixed switch or circuit breaker that is accessible from the floor. The switch must be locked in the open position. Cab operated cranes or hoisting mechanisms must have the switch or circuit breaker located within easy reach of the operator. Controllers-must be in off position. Main or emergency switch-locked in open position. Out of Order signs must be visibly posted. POWERED INDUSTRIAL TRUCKS 29 CFR 1910.178 -- Disconnect the battery before making any repairs to the trucks electrical system. WOODWORKING MACHINERY 29 CFR 1910.213 -- Power driven woodworking machines must have a disconnect switch that can be locked in the off position during repairs or adjustments. WELDING 29 CFR 1910.252 -- Must purge/clean all tanks, vessels, barrels, drums - prior to welding& cutting to prevent explosion and generation of flammable/toxic gases. All pipelines to the drum or vessel must be disconnected and blanked. ELECTRICAL STANDARD 29 CFR 1910.333 Can have two written programs that address electrical Lock out Tag out or one that complies with 29 CFR 1910.147 if it covers sections (c)thru(f) and the inherent electrical hazards. Must treat conductors or electrical parts that have not been locked and tagged out as "energized". Only qualified electricians can work on energized systems. Cannot substitute interlocks on electrical equipment for lockout/tagout. Must discharge capacitors. High capacitance elements must be short-circuited and grounded. ----------------- Mohammad Imran HVAC Engineer

Bearing & Types of Bearing

bearings A mechanical bearing is a component used between two parts that allows rotational or liner movement, reducing friction and enhancing performance to save energy. Both metal and plastic bearings can be found everywhere, from refrigerators to computers to the 100 or so bearings found in your car. The concept behind them is a simple one: things roll better than they slide. Without bearings, the wheels in your car would rattle, the transmission gear teeth wouldn’t be able to mesh, and the car wouldn't run smoothly. They are composed of a smooth inner and outer metal surface for metal balls to roll against. The balls or rollers help “bear” the load and the device functions more efficiently. There are many different types of bearings, each used for specific purposes and designed to carry specific types of loads, radial or thrust. Here, we’ll look at the 6 most popular types: plain bearings, rolling element bearings, jewel bearings, fluid bearings, magnetic bearings, and flexure bearings. 1) Plain Bearings Plain bearings are the simplest type of bearing and are composed of just the bearing surface with no rolling elements. They have a high load-carrying capacity, are generally the least expensive and, depending on the materials, have much longer lives than other types. 2) Rolling Element Bearings Rolling element bearings place balls or rollers between two rings – or “races” – that allows motion with little rolling resistance and sliding. These bearings include ball bearings and roller bearings. Ball bearings are the most common type of rolling element bearing. These bearings can handle both radial and thrust loads but are usually used where the load is relatively small. Because of its structure, there is not a lot of contact with the balls on the inner and outer races. If the bearing is overloaded the balls would deform and ruin the bearing. Roller bearings are able to handle a much heavier, radial load, like conveyor belts, because they don’t use balls. Instead, they have cylinders allowing more contact between the races, spreading the load out over a larger area. However this type of bearing is not designed to handle much thrust loading. 3) Jewel Bearings Jewel bearings are plain bearings with a metal spindle that turns in a jewel-lined pivot hole. They carry loads by rolling the axle slightly off-center and are usually used in mechanical watches or clocks. This is due to their low and predictable friction that improves watch accuracy. 4) Fluid Bearings Fluid bearings support their load using a thin layer of gas or liquid and can be classified into two types: fluid-dynamic bearings and hydrostatic bearings. Fluid-dynamic bearings use rotation to form the liquid into a lubricating wedge against the inner surface. In hydrostatic bearings, the fluids – usually oil, water, or air – rely on an external pump. Fluid bearings are used in high load, high speed or high precision applications that ordinary ball bearings either couldn’t handle or would suffer from increased vibration and noise. 5) Magnetic Bearing Magnetic bearings support moving parts without physical contact, instead relying on magnetic fields to carry the loads. They require continuous power input to keep the load stable, thus requiring a back-up bearing in the case of power or control system failure. Magnetic bearings have very low and predictable friction and the ability to run without lubrication or in a vacuum. They are increasingly used in industrial machines like turbines, motors, and generators. 6) Flexure Bearing A typical flexure bearing is one part joining two others, like a hinge, in which motion is supported by a load element that bends. These bearings require repeated bending, so material selection is key. Some materials fail after repeated bending, even at low loads, but with the right materials and bearing design the flexure bearing can have an indefinite life. Another notable characteristic of this bearing is its resistance to fatigue. Many other bearings that rely on balls or rollers can fatigue as the rolling elements flatten against. -----'-------------- Mohammad Imran HVAC Engineer

Heat Load calculation in term of HVAC

Heat load or heat gain A building or room gains heat from many sources. Inside occupants, computers, copiers, machinery, and lighting all produce heat. Warm air from outside enters through open doors and windows, or as ‘leakage’ though the structure. However the biggest source of heat is solar radiation from the sun, beating down on the roof and walls, and pouring through the windows, heating internal surfaces. The sum of all these heat sources is know as the heat gain (or heat load) of the building, and is expressed either in BTU (British Thermal Units) or Kw (Kilowatts). For an air conditioner to cool a room or building its output must be greater than the heat gain. It is important before purchasing an air conditioner that a heat load calculation is performed to ensure it is big enough for the intended application. Heat load calculations There are several different methods of calculating the heat load for a given area: Quick calculation for offices For offices with average insulation and lighting, 2/3 occupants and 3/4 personal computers and a photocopier, the following calculations will suffice: Heat load (BTU) = Length (ft.) x Width (ft.) x Height (ft.) x 4 Heat load (BTU) = Length (m) x Width (m) x Height (m) x 141 For every additional occupant add 500 BTU. If there are any additional significant sources of heat, for instance floor to ceiling south facing windows, or equipment that produces lots of heat, the above method will underestimate the heat load. In which case the following method should be used instead. A more accurate heat load calculation for any type of room or building The heat gain of a room or building depends on: The size of the area being cooled The size and position of windows, and whether they have shading The number of occupants Heat generated by equipment and machinery Heat generated by lighting By calculating the heat gain from each individual item and adding them together, an accurate heat load figure can be determined. Step One Calculate the area in square feet of the space to be cooled, and multiply by 31.25 Area BTU = length (ft.) x width (ft.) x 31.25 Step Two Calculate the heat gain through the windows. If the windows don’t have shading multiply the result by 1.4 North window BTU = Area of North facing windows (m. sq.) x 164 If no shading, North window BTU = North window BTU x 1.4 South window BTU = Area of South facing windows (m. sq.) x 868 If no shading, South window BTU = South window BTU x 1.4 Add the results together. Total window BTU = North window + South window Step Three Calculate the heat generated by occupants, allow 600 BTU per person. Occupant BTU = number of people x 600 Step Four Calculate the heat generated by each item of machinery - copiers, computers, ovens etc. Find the power in watts for each item, add them together and multiply by 3.4 Equipment BTU = total equipment watts x 3.4 Step Five Calculate the heat generated by lighting. Find the total wattage for all lighting and multiply by 4.25 Lighting BTU = total lighting watts x 4.25 Step Six Add the above together to find the total heat load. Total heat load BTU = Area BTU + Total Window BTU + Occupant BTU + Equipment BTU + Lighting BTU Step Seven Divide the heat load by the cooling capacity of the air conditioning unit in BTU, to determine how many air conditioners are needed. Number of a/c units required = Total heat load BTU / Cooling capacity BTU

VRF&VRV

VRV or VRF ? What’s the difference between VRV and VRF? Many people who ask this question, mistakenly interpret it as 2 different HVAC technologies. Actually, those are two different terms for the same type of HVAC technology. Based on Inverter technology compressors, the first VRV HVAC systems were invented by Daikin during the early 1980’s. As a technology leader in the HVAC industry, Daikin had registered the VRV term (which stands for Variable Refrigerant Volume1) as an official trademark. All other companies use VRF (Variable Refrigerant Flow2) for their similar HVAC systems. Eventually, VRF is the more common term for these types of systems, and this is the term that will be used for the rest of the article. Wish to integrate your VRF to Home Automation system? Check out our simple solutions. So what is VRF? It can easily be related to as the “Rolls Royce” of Air Conditioning Systems. It’s a very sophisticated technological air conditioning system, based on several principles: Refrigerant only – where refrigerant is the only coolant material in the system (in contrary to the chilled water systems, where refrigerant is used for cooling/heating the water that is circulated throughout the whole system). Inverter compressors that allow lowering power consumption with partial cooling/heating loads. Several air handlers (indoor units) on the same refrigerant loop / circuit. Ability of modular expansion (especially applicable for large projects, that can grow in stages). Typical VRF system structure A typical system consists of an outdoor unit (comprising one or multiple compressors), several indoor units (often and mistakenly called “fan coils”), refrigerant piping, running from the outdoor to all indoors, using Refnet Joints (copper distributors in pipes) and communication wiring. VRV / VRF HVAC connectivity diagam Communication wiring consists of a 2 wired cable, chained from the outdoor to all indoors, creating an internal closed loop network, that is an essential part of any VRF installation. As for the Control, each indoor is controlled by its own wired control panel, while there are some possibilities for wireless remotes (IR) and centralized controllers, enabling controlling all indoors from one location. How does VRF HVAC work? The operation logic of the VRF is fully built-in inside the system and is proprietary for each VRF manufacturer. The system gets inputs from the user (e.g. desired comfort temperature) and from the surroundings (outside ambient temperature), and according to that data it implements its logic in order to get to the desired comfort conditions, utilizing optimal power consumptions. The ability to adjust itself to the outdoor conditions is one of the main factors that makes these systems so efficient, compared to the traditional water cooled systems, based on chillers and fan coils. Now, let’s dive in, and see how it works in details. Let’s take as an example a typical VRF installation, with one outdoor unit and multiple indoors. At the beginning, the system is in standstill condition (everything is turned off). Once a user turns one of the indoors “ON” by its local remote, the outdoor “gets noted” regarding it, and starts working. At this point, it will examine the outdoor conditions (temperature), the operating indoor requirements (operation mode, set point temperature), and will operate the compressor at the exact level, required to comply with the indoor requirements. When another indoor unit is turned on, the outdoor recalculates the requirements from all the indoors, and will increase the compressor’s output, according to the required level of demand. This process is constantly occurring with any change, performed in the HVAC system. As described, this system is fully automatic, and regulates its power consumption based on the demand arriving from the indoor units and outside prevailing conditions. User can have influence on the desired indoor comfort conditions, modifying: Operation mode (on/off), Operation state (Cool/Heat/Fan/Dry/Auto), setpoint temperature, fan speed (high/medium/low/auto). Controlling those parameters is the only thing required for proper operation, and the only thing that is required for proper integration with the VRF system. VRF System types Cooling only systems (less popular) – those systems can only cool. Heating is not available. Fan and Dry modes are available for each indoor unit independently. Heat Pump systems (most popular) – all the indoor units can either heat, or cool (not at the same time). Fan and Dry modes are available for each indoor unit independently. Heat Recovery systems (less popular) – those systems are the most sophisticated ones, where cooling and heating may be available by each indoor unit, independently, at the same time.

VFD

A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter. ---------------------- Mohammad Imran HVAC Engineer

Compressor Over load

The overload relay is a protection device used in the compressor circuit on your refrigerator. Power is applied to the compressor motor windings through the overload device, and the relay is used to add the start winding in the circuit until the compressor is at running speed. ----------------------- Mohammad Imran HVAC Engineer

What is surge

In a centrifugal compressor, 'surge' is a name given to a dangerously unstable gas condition in the compressor and condenser. Put simply, it occurs when the forward compression thrust of gases in the compressor wheel falls below the critical velocity of the gas to flow forward through the condenser.Apr

Cause of surging in chiller

The flow separation will eventually cause a decrease in the discharge pressure, and flow from suction to discharge will resume. Surging can cause the compressor to overheat to the point at which the maximum allowable temperature of the unit is exceeded. ... This is defined as the surge cycle of the compressor.. --------------------- Mohammad Imran HVAC Engineer

Water treatment process

Community Water Treatment Drinking water supplies in the United States are among the safest in the world. However, even in the U.S., drinking water sources can become contaminated, causing sickness and disease from waterborne germs, such as Cryptosporidium, E. coli, Hepatitis A, Giardia intestinalis, and other pathogens. Drinking water sources are subject to contamination and require appropriate treatment to remove disease-causing agents. Public drinking water systems use various methods of water treatment to provide safe drinking water for their communities. Today, the most common steps in water treatment used by community water systems (mainly surface water treatment) include: Figure illustrating the water treatment cycle, showing coagulation, sedimentation, filtration, and disinfection Figure courtesy of EPA Coagulation and Flocculation Coagulation and flocculation are often the first steps in water treatment. Chemicals with a positive charge are added to the water. The positive charge of these chemicals neutralizes the negative charge of dirt and other dissolved particles in the water. When this occurs, the particles bind with the chemicals and form larger particles, called floc. Sedimentation During sedimentation, floc settles to the bottom of the water supply, due to its weight. This settling process is called sedimentation. Filtration Once the floc has settled to the bottom of the water supply, the clear water on top will pass through filters of varying compositions (sand, gravel, and charcoal) and pore sizes, in order to remove dissolved particles, such as dust, parasites, bacteria, viruses, and chemicals. Disinfection After the water has been filtered, a disinfectant (for example, chlorine, chloramine) may be added in order to kill any remaining parasites, bacteria, and viruses, and to protect the water from germs when it is piped to homes and businesses.