Buy McQuay Expansion Valve Parts

McQuay Expansion are key parts of the ACU Split System Air Conditioners. A thermal expansion - 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 .


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

Thermal Expansion

Expansion are used to modulate refrigerant flow to the evaporator. There are several types of expansion 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 require significant controls to operate and normally are used if they were included as part of the original equipment.

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

TX are sized by:

• Refrigerant type

• Refrigeration circuit capacity

• Pressure drop across the

• Equalization (internal or external)

For smaller systems, an internally equalized TX 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 is recommended. An external line accounts for the pressure drop through the evaporator which becomes an issue on larger evaporator coils.

TX and distributors (common with air coils) should be installed in vertical pipes. If a TX 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 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 should be sized as close to capacity as possible. Use of nominal TX 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 for each distributor. For large DX field applications there are often multiple refrigeration circuits, each with its own compressor, evaporator circuit, and TX . 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 and solenoid 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 and a hot gas bypass . Some manufacturers provide a single device that provides the functions of both a solenoid and control . The solenoid is energized when hot gas bypass is required. The hot gas bypass 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 . 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.