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Buy McQuay Expansion Valve Parts

McQuay Expansion Valves are key parts of the ACU Split System Air Conditioners. A thermal expansion valve - TXV- which can be made apart of the evaporator coils, will bring about improved refrigerant management. If low suction pressure occurs, then the probable cause could be that the bulb of the TXV has lost its charge. Systems like the Enfinity water source heat pumps are much more effective and bring about savings due to use of such parts like these efficient valves.

Motorized Valve

McQuay Motorized Valve and Relay kit is a field-installed accessory for use with a MicroTech III Unit Controller or Mark IV Unit Controller. The Motorized Valve and Relay is provided with either two pins (female) or three pins, depending on the valve selected. The 2 and 3 the motorized valve will open on a call for compressor operation. Valves for unit sizes 007 to 019 are 1/2" while unit sizes 024 to 070 are 3/4".

Thermal Expansion Valves

Expansion valves are used to modulate refrigerant flow to the evaporator. There are several types of expansion valves including:

• Fixed area restrictor (capillary and orifice types)

• Automatic (constant pressure)

• Thermal expansion (TX)

• Electronic

For field-piped systems, the TX and electronic types are commonly used. Electronic valves require significant controls to operate and normally are used if they were included as part of the original equipment.

TX valves (Figure 15) are excellent for DX systems because they modulate refrigerant flow and maintain constant superheat at the evaporator. As superheat climbs, the TX valve opens allowing more refrigerant to flow. As superheat drops, the valve closes to maintain superheat.

TX valves are sized by:

• Refrigerant type

• Refrigeration circuit capacity

• Pressure drop across the valve

• Equalization (internal or external)

For smaller systems, an internally equalized TX valve is acceptable. For larger systems (greater than 2 PSI (13.8kPa) pressure drop across the evaporator, or if a distributor is used) an externally equalized TX valve is recommended. An external line accounts for the pressure drop through the evaporator which becomes an issue on larger evaporator coils.

TX valves and distributors (common with air coils) should be installed in vertical pipes. If a TX valve with a distributor is installed in a horizontal pipe, there is a possibility that the liquid portion of the two-phase flow downstream of the TX valve will fill the distributor tubes on the bottom, leading to different refrigerant flow rates in the individual tubes. This is not an issue with nozzles (common with chillers), so horizontal installations are acceptable.

TX valves should be sized as close to capacity as possible. Use of nominal TX valve capacity is discouraged. Under-sizing up to 10% is acceptable if there will be significant part load operation. Higher superheat conditions at full load are allowable.

There must be one TX valve for each distributor. For large DX field applications there are often multiple refrigeration circuits, each with its own compressor, evaporator circuit, and TX valve. Evaporator circuits may be in a common evaporator coil such as interlaced, face split, or row split type. On occasion where there are multiple evaporators on a common refrigeration circuit, separate TX valves and solenoid valves are required for each evaporator.

Hot Gas Bypass

Hot gas bypass is a method of maintaining compressor suction pressure (creating a false load) during light loads. This has the affect of modulating compressor capacity below the minimum unloading point without cycling the compressor. It is accomplished by returning hot (discharge) gas from the leaving side of the compressor back to a point on the low-pressure side of the refrigeration circuit.

Hot gas bypass lines include a solenoid valve and a hot gas bypass valve. Some manufacturers provide a single device that provides the functions of both a solenoid and control valve. The solenoid valve is energized when hot gas bypass is required. The hot gas bypass valve modulates the refrigerant flow through the line to maintain the suction pressure.

Mcquay manufactures products like the Enfinity systems which provide low cost installation, standard or extended range or geothermal application flexibility, superior indoor air quality, cheaper maintenance and service, quiet and highly reliable operation. Systems like the Enfinity water source heat pumps are much more effective and bring about savings due to use of such parts like these efficient valves. Making such user friendly products, the company has become one of the major players in the HVAC market. At HVACPLUS, we are host to almost all parts required for the different applications developed by the company. Apart from this we are also host to many other top heating, ventilation, Air conditioning and refrigeration systems makers like Trane, AAF, Carrier, Barber Coleman, York, Honeywell, Herman Nelson and many more.


McQuay expansion valves are important components of the ACU Spit System Air Conditioners. One of these valves is the TXV, or thermal expansion valve, which is created separate from the evaporator cols, and brings forth better management of refrigerant. Low suction pressure can happen, and if it does, then the likely cause will be that there has been a loss of charge in the TXV bulb. The Enfinity water source heat pumps are more effective and efficient than most others and can help customers to save their dollars.

Motorized Valves

The McQuay Motorized Valve and Relay kit can be installed in the field and is an accessory that can be used with various controllers. This motorized valve and relay contains two or three pins, and this varies depending on the valve. The motorized valve opens on a call for operation of the compressor. There are several sizes of units that these valves operate with.

Thermal Expansion Valves

These expansion valves are utilized to keep refrigerant flowing to the evaporator. These valves include:

Capillary and orifice fixed area restrictors

Constant automatic pressure

TX or thermal expansion

Electronic valves

Systems that are field-piped use electronic types and TX types of valves. The electronic valves call for certain controls to run normally and are used along with the equipment in its original state.

TX valves are great for DX mechanisms because they maintain flow of refrigerant and the consistent application of the evaporator's superheat. When superheat increases, the valve opens and lets more refrigerant flow properly. When superheat decreases, the valve is closed.

TX valves can be categorized by the following sizes:

Type of refrigerant

The capacity of the refrigeration circuit

Dropping pressure across the valve

External or internal equalization

The systems that are smaller use a TX valve that provides internal equalization. Pressure can also drop when crossing the evaporator. A distributor can be used as well, which requires a TX valve that offers external equalization. This external line means that the pressure drop across the evaporator turns into an issue for the evaporator coils that are larger.

The common air coil valves and distributors need to be placed in pipes that are vertical. If a TX valve along with a distributor is placed in a pipe that is horizontal, it is possible that the liquid of the flow which is downstream from the TX valve will fill up the tubes of the distributor on the bottom, which leads to different flow rates of refrigerant in the separate tubes. With nozzles that are found commonly with chillers, this is not an issue, so it is acceptable to use horizontal installations.

The TX valves need to be kept sized close to their capacity as much as possible. The use of the capacity of nominal TX valves is not encouraged. It is possible to undersize these valves up to ten percent if there will be a larger part load of operation. The higher conditions of superheat at full load capacity are permissible.

Each distributor needs to have at least one TX valve. The larger DX applications of the field often allow for several circuits for refrigeration. Each of these has an individual compressor, a TX valve, and an evaporator circuit. Circuits for the evaporator may be in the same evaporator coil including row split types, face splits, or interlaced circuits. There can also be more than one evaporator on a single refrigeration circuit and individual separate valves, including solenoid and TX valves, are needed for each evaporator.

Bypass of Hot Gases

The bypass of hot gases is a way to keep the suction pressure of compressors, which create a load that is false, during the lighter loads. The effect of keeping compressor capacity modulated and lower than the least unloading point means that the compressor does not need to cycle. This is achieved by returning the discharged vapors from the discharge side of the compressor to the point on the refrigeration circuit that is the low pressure side.

The bypass lines have a solenoid valve and bypass valve for hot vapor. A few of the manufacturers allow an individual device that allows the uses of both a control and solenoid valve. The solenoid valve becomes energized when the bypass of the hot vapors is needed. The bypass valves control the flow of refrigerant via the line to keep the suction pressure constant.

McQuay makes products such as the Enfinity systems, which offer installation that is low-cost, a standard or extended array of applications for geothermal adaptability, improved quality of indoor air, lower cost service and maintenance, and operation that is quiet and dependable. Systems such as the Enfinity water source heat pumps are proficient and can help save money and energy due to valve efficiency. The user-friendly products such as the ones that McQuay manufactures have helped McQuay become a major name in the HVAC field. At HVACPLUS, we offer a large array of parts needed for an expansive range of applications. Separate from this, we also host supplies that are made by many different manufacturers, including Barber Coleman, Trane, York, Herman Nelson, Honeywell, Carrier, and AAF, all of whom are important companies in the heating, ventilation and air conditioning and refrigeration field.