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.

Role of vacuum in RAC

A vacuum is maintained in the condenser so that steam can easily flow and more work can be extracted from the steam in the turbine. How does the condensate extraction pumps take suction from such a low pressure condensor. ---------------'-----' Mohammad Imran HVAC Engineer

Filter Driers

Filter driers are devices used in a HVAC system that are a combination of filter and dryer (or drier). A filter is used to remove any particle such as dirt, metal or chips from entering the refrigerant flow control. The refrigerant flow control device could be thermostatic expansion valve or simply a capillary tube.

The filter is sometimes also referred to as a strainer. It is critical that these particles are filtered out and prevented from going into the metering device. It can cause blockage to the passage flow of the refrigerant in the expansion valve and cause improper operation to the system.

A drier as its name imply is used to remove the moisture from the refrigerant. Sometimes it is also referred to as dehydrator or dryer. It is necessary to remove moisture from the system otherwise it may freeze inside the tube causing the flow of refrigerant to be restricted. The moisture will also cause the formation of acids and sludge when in contact with oil in the system.

These devices are usually used in bigger system where the refrigerant circuit is designed for field service. Residential units that are charged with refrigerant at factory level and hermetically sealed do not use these devices as the possibility of moisture and particles entering the system is minimal.

Types of Filter

There are basically two types in used today.

• Liquid Line Type
• Suction Line Type

Liquid Line Type is placed after the condenser coil and before the expansion valve. The liquid refrigerant that flows from the condenser to the expansion valve is filtered from particles and moisture before entering it. Good filter will filter out particles that are 20 micron or above from the system.

Some higher end device has sight glass that enables the technician to look into it to see the level of refrigerant. Some have chemical in it that indicate the amount of moisture in the system based on the color of it.

The Emerson EK-164 liquid line drier shown below is able to remove moisture and acid from the liquid refrigerant. It can also remove particles that are bigger than 20 micron from the refrigerant system. It has a maximum operating pressure of 680 psig and painted with a corrosive resistance epoxy powder paint. Suitable for outdoor installation.

Emerson EK-164 liquid line filter driers being installed on site.

Suction Line Type is placed after the evaporator and before the compressor. This device is used to protect the compressor especially after any failure that contaminates the system.

Motor failure in the compressor usually cause acid and other contaminants to be introduced into the refrigerant system hence it is important to have the suction line filter dryer installed.

Capacitor Failure

Valve and Actuator

Two components are heavily relied upon in the industrial and manufacturing sectors, and these are the actuator and the valve. And while both of these implements are related, they do serve very different functions.

Here are the factors that separate actuators from valves.

What Does a Valve Do?

The primary job of a valve is to control the flow of a fluid or gas within a line. There is an array of valve types, and each one operates uniquely, however, in the end, the core principles are the same. Some of the most common valve styles are 2-way valves and 3-way valves, both of which operate with either air pressure, electrical current, or hydraulic fluid.

What Does an Actuator Do?

An actuator is an implement that is built into the valve housing which dictates when the valve will open or close through the use of a controller system. As with valves, there are some different types of actuators to choose from, depending on the application in which it will be used. A few examples of actuator types are manual linear actuators, rotary actuators, and fluid power rotary actuators.

What is the Difference Between a Valve and an Actuator?

As it has been shown, valves and actuators are two completely separate components; however, they do work together to accomplish a common task. Therefore, it can be said that a valve is a physical part of a system that opens and closes to dictate the amount of fluid being allowed to pass through, while the actuator tells the valve when to operate.

For instance, in a heated flooring system, fluids of varying temperatures are pumped beneath the floor structure to help maintain a preset temperature. And while the system will work with only a valve, there will be no way to control the functioning of the valve, other than by manual methods. This would mean that a human would have to continually monitor the temperature of the floor, and adjust the valve when changes are necessary.

However, if an actuator is installed with the valve, the actuator can be set through the use of a computer controller to open and close the valve at a specific time or to meet certain criteria, and in this case, the criteria would be the fluid temperature.

Conclusion

Often valves and actuators are mistakenly considered to be the same thing, but in fact, they are two very different components. While a valve is used to control the amount of fluid or gas flowing through a pipe, it must either be set in a specific position or manually controlled. However, through the use of an actuator, which is an implement that is installed directly into the valve, the valve can be programmed to open and close at specific intervals.

The actuator is typically controlled by a computer system that uses various sensors which dictate the action of the actuator and thus the valve. In the end, valves and actuators are completely separate components in a fluid transfer system, but they are used together to achieve a single goal.

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Cause of water leakage from RAC

Why is Air Conditioner Leaking Water Inside

Here’s a common question we get during Florida summers, “Why is my AC leaking water inside my home?There are multiple causes of this problem.

But first, turn your AC’s thermostat to “Off” to prevent further damage to your home.

To understand why this is happening, you need to know how water forms on your AC in the first place.

Why does water form in my air conditioner?

Your AC’s inside unit contains the evaporator coil (pictured on the right) that cools the warm air blown over it. This causes condensation (moisture) to form on the coil, just like how water droplets form on a cold glass of water on a hot day.

The moisture on the coil drips into a drain pan and down a condensate drain line (a white PVC pipe) that leads out your home.

So, with all that in mind, here are a few things that cause that water to leak into your home.

Cause 1: Clogged condensate drain line

A clogged condensate drain line is the most common cause of water leaking from your AC into your home.

If the drain line gets clogged with dust, dirt, sludge or mold, that water backs up into your home. In that case, you’ll need to unclog it. There are multiple unclogging methods, like using a wet/dry vac on the condensate line.

But the surefire way is to have a professional use a special vacuum to suck the blockage material

Cause 2: Damaged/rusted drain pan

Got an old air conditioner (12-15 years)? The drain pan may be damaged or rusted through, so water just falls right through. You’ll need to replace the pan.

Cause 3: Broken condensate pump

Is your furnace and indoor AC unit installed in the basement? If so then there is a condensate pump that pumps the water outside. But if the pump breaks, the water isn’t being pumped outside anymore. You will need to repair or replace the pump.

Cause 4: Dirty air filter

A dirty air filter blocks airflow over the evaporator coil. When that happens, the evaporator coil gets too cold and freezes over. When it melts, it drips an excess amount of water that the pan may not be able to handle.

Check your air filter to see if it’s dirty and change it if needed. You should be changing it every 1-3 months (depending on the season)

Cause 5: Low refrigerant

Similar to a dirty air filter, low refrigerant will lower pressure in the AC system, causing the evaporator coil to freeze over. When the coil melts, water overflows the drain pan.

You’ll notice you’re low on refrigerant when:

• The air conditioner isn’t cooling well
• You hear a hissing or bubbling noise (indicating a refrigerant leak)

Depending on the severity of the refrigerant leak you’ll either repair the leak or replace the whole AC unit.

If you need a new one, read our article,

Need a professional?

If changing the air filter did not help, contact Cool Today to 

Also, ask us about installing a float switch on your air conditioner if it does not have one already. This switch will shut down the air conditioner in case it overflows with water again.

Compressor failur cause

So you’ve been told that your AC compressor’s “gone bad.” This will likely lead you to a series of questions. Questions like, how did this happen? How much is this going cost me? And what exactly is an AC compressor, anyway?

What Is an AC Compressor?

First things first: The compressor in an air conditioning unit is the “heart” of your system. It is usually located with the condenser and the fan in the outside “box” portion of your AC unit. Contrary to popular perception, AC units don’t add cool air to a space, but rather take heat out of it. The compressor’s role in this process is a critical one.

Refrigerant chemical enters the compressor as a cool gas, and the compressor squeezes it until it is a very hot gas under very high pressure. This allows it to run through the condensing coils and allows the heat to dissipate outside, and eventually evaporate in the end of the cycle through another set of coils, actually removing the heat from the air through this process, blowing it out of the house until the inside is a comfortable temperature.

How Did It Happen?

Compressors are actually very dependable (lasting on average between 12-15 years) so typically, when your AC compressor has gone bad there’s an underlying cause that needs to be addressed lest the problem reemerge even after the unit has been replaced.

There are many ways a compressor can give up the ghost. Nearly all of them are easily preventable with proper, routine maintenance. Some of the usual offenders include:

• Refrigerant floodback
  The liquid refrigerant doesn’t completely vaporize in the evaporator, returning into the compressor cylinder and damaging it with runaway pressure. There are many ways this can happen, from refrigerant overcharge to improper settings.
• Lack of lubrication
  An oil leak, oil trapped in the suction line, and oil pump failure are some of the ways in which the compressor can fail due to oil contamination.
• System Contamination
  The causes of compressor failure due to system contamination can include such elements as air, moisture, dirt, and acids which can form with the addition of heat and pressure.
• Electrical problems
  The main causes of electrical failure include imbalances in the voltage or current, resulting in overheating and failure.
• Overheating
  A compressor may overheat if there is not enough suction cooling, lack of condenser cooling, or if there is air in the system, raising both the pressure and temperature.

Refrigerant colour code

CFCs

Number	Cylinder Color	Refrig. Name	Application
R-11	Orange	Trichloromonofluoromethane	Centrifugal Chillers
R-12	White	Dichlorodifluoromethane	Reciprocating and rotary equipments
R-13	Light Blue	Monochlorotrifluoromethane	Used in low stage of cascade systems
R-13B1	Coral	Bromotrifluoromethane	Low to Medium temperature applications
R-113	Purple	Trichlorotrifluoroethane	Low capacity centrifugal chillers
R-114	Dark Blue	Dichlorotetrafluoroethane	High capacity Chillers
R-500	Yellow	Refrig. 152A/12	Industrial and commercial reciprocating compressors
R-502	Light Purple	Refrig. 22/115	Reciprocating and rotary equipments
R-503	Aquamarine	Refrig. 23/13	Low temperature commercial refrigeration

HCFCs 

Number	Cylinder Color	Refrig. Name	Application
R-22	Light Green	Monochlorodifluoromethane	Residential, commercial and industrial
R-123	Light Gray	Dichlorotrifluoroethane	R-11 replacement for centrifugal chillers
R-124	Deep Green	Chlorotetrafluoroethane	Medium pressure chillers
R-401A	Coral Red	R-22 + R-152a + R-124	Medium temperature systems
R-401B	Mustard Yellow	R-22 + R-152a + R-124	Transport refrigeration, domestic refrigerators
R-402A	Light Brown	R-22 + R-125 + R-290	Ice machine, vending, supermarket and food service
R-402B	Green Brown	R-22 + R-125 + R-290	Supermarket, food service and transport

HFCs

Number	Cylinder Color	Refrig. Name	Application
R-23	Light Gray	Trifluoromethane	Low temperature refrigerant
R-134a	Light Sky Blue	Tetrafluoroethane	Automotive industry and refrigeration systems
R-404A	Orange	R-125 + R-143a + R-134a	Medium and low temperature
R-407C	Chocolate Brown	R-32 + R-125 + R-134a	R-22 Replacement
R-410A	Rose	R-32 + R-125	Replacement for residential air conditioning
R-507	Light Brown	Refrig. 23/13

https://www.blogger.com/blogger.g?blogID=4744402466049114883#editor/target=post;postID=3680206906830045754

MOHAMMAD IMRAN

HVAC Engineer

This will cause the following symptoms failure of Exoension Valve:

• Low evaporator (suction) pressure;
• High evaporator and compressor superheats;
• Low compressor amp draw;
• Short-cycling on the low-pressure control;
• Somewhat high discharge temperature;
• Low condensing (head) pressure;Low condenser split; 

Safety factor in HVAC field.

The Seven Greatest Safety Threats to HVAC Contractors

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Safety Threats to HVAC Contractors

The HVAC industry provides many professionals with rewarding and secure careers. Controlling the internal climate environments of offices, homes, and other spaces is considered a necessity today. In addition to this growing demand, the technology used in HVAC equipment requires knowledgeable and experienced personnel.

However, both this technology and other factors mean there are certain occupational hazards and risks that accompany the HVAC profession. Taking time to be knowledgeable about these factors will improve the efficiency of any HVAC firm and its employees while minimizing potentially catastrophic risks.

While there are a virtually unlimited number of dangers in any such business, there are seven issues that top the list of concerns for HVAC firms and workers. Below is a brief discussion of those risks that you can evaluate relative to your own operations:

1. Wiring-related Risks. Of course, the primary risk for any electrical equipment work is electrocution. When working with wiring day in and day out, it is easy to become complacent about picking up a cable or wire and attempting to work with it. It is essential to always treat every wire as live and handle all wiring and cabling with the care they deserve.
2. Equipment-based Risks. Specific risks are addressed below, but the very size, weight and complexity of the majority of HVAC equipment presents special dangers to personnel. Moving components such as fans and pulleys present unique dangers, especially when they are part of larger units. The many sharp edges and components of an HVAC unit present multiple risks of cuts, punctures, scrapes and other dangers.
3. Environmental/Exposure Risks. The chemicals used as refrigerants can be a danger to personnel, especially when working with larger and older systems that have developed leaks. Another major factor is the issue of asbestos exposure, often a concern in the same older facilities.
4. Fatigue-related Issues. Each of the other risks listed here are magnified by the factor of fatigue and complacency. It is possible to execute a dangerous connection or other operation hundreds of times and then make a critical error at some point because of fatigue or inattention. Many HVAC installations are made under tight deadlines to meet construction schedules and this increases the chance for a team of installers to be worked to a point where such accidents are more likely. The other side of this issue is complacency, or executing a dangerous step so many times that there is a loss of appreciation for its inherent danger.
5. Safety Violations. Many accidents occur when one person is injured because another breaks a standard safety procedure, such as removing an interlock or failing to properly secure tools when working at a height. Following safety rules is not just important for the individual, it is essential for protecting co-workers as well.
6. Burns and related Injuries. The danger of working with extremely hot and moving components often exists when performing regular or emergency maintenance or repairs on installed equipment. This is especially the case when some parts seem to be off and cool while other components nearby are operating at extreme temperatures. The larger the installation being serviced, the greater the risk of misjudging the status of any one unit or component.
7. Falls and Crushing Injuries. When installing or removing larger HVAC units, the work often involves use of third-party cranes and equipment. Workers have to pay special attention to their risks when working at heights or when moving multi-ton HVAC components.    

Coefficient of performance ( COP )

Coefficient of performance. The efficiency of a refrigerator or heat pump is given by a parameter called the coefficient of performance (COP). The COP of a refrigerator is given by the following equation: COP = Desired Output/Required Input = Cooling Effect/Work Input = QL/W.

Fan Coil Unit F.C.U

Fan Coil Unit Systems. A fan coil unit(FCU) contains a fan which draws the air in a space into the unit then blows it over a cooling or heating coil. The air comes out of the FCU either cooler or hotter than before.

WORKING PRINCIPLE OF AN AHU

Air Handling unit or AHU is an assembly of air conditioning components (such as fans, cooling coils, filters, humidifiers and dampers) integrated into a self-contained package and installed as a single unit, which is connected to system of metal duct work that distributes the conditioned air.

We difference two types of AHU :

• simple flow: the AHU whether works in 100% fresh air, or air intake, or works with the two of them.
• dual flow: the AHU is working with the most optimal configuration, by chosing between quantity of fresh air, total treated air, air intake, return air, according to the situation.

How does a simple flow AHU work ?

It is actually very easy to understand : the AHU pumps the designed external air, which will be treated in temperature and humidity, as well as quality of composition with different type of filters. This treated air will be carried to respective areas by means of ducting.

For a dual flows AHU, besides the first objective explained previously, the AHU will extract the air from the areas that can’t be recycled back in the AHU  (air too polluted or areas which requires a percentage of extracted air), and will be rejected out of the structure.

Objectives of the AHU :

• Fresh air intake (which replaces the air polluted)
• Air treatment (by filtration)
• Humidity and temperature control of the air supply
• Structure easy to install in each type of architectural configuration
• Minimal surface facilities required (specification important due to the m² price today).
• Noise reduction (no need to open any windows)
• Integrated regulation with an software adapted to health services
• Plug and Play unit.
• Reduction of the ductwork and installation – Important saving of time and money..

The AHU provide pre cooling (pre heating) of the ventilation air and thus take care of only a relative small part of the cooling (heating) load. In addition the energy for pre cooling (pre heating) does not come from the AHU itself, but is provided by an external source, such as a chiller (boiler or furnace).

Some AHUs like dual stream VMC are working with exchanges boxes for effecting heat energy recovery, thanks to the use of the heating recovered to heat up the air intake.

The dual flows AHUs know how to work according to different working systems.

The different types of filtration:

• Total recycling : no fresh air is brought, air traitment is working as closed circuit, only with the ambient air,
• Partial rcycling : part of the air treated is rejected and replaced by fresh air.
• 100% Fresh air : the air intake flow equals to the air supplied. It becomes therefore interesting to retrieve the energy brought by a heat recovery unit on the air intake “polluted”.