Category: Controlling Refrigerant

HVAC Crankcase Pressure-Regulating Valves

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HVAC Crankcase Pressure-Regulating Valves

Crankcase pressure-regulating valves are designed to prevent overloading of the compressor motor. They limit the crankcase pressure during and after a defrost cycle or after a normal shutdown period. When properly installed in the suction line, these valves automatically throttle the vapor flow from the evaporator until the compressor can handle the load. They are […]

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HVAC Float valve

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A float valve, either high-side or low-side, can serve as a metering device. The high-side float, located in the liquid line, allows the liquid to flow into the low side when a sufficient amount of refrigerant has been condensed to move the float ball. No liquid remains in the receiver. A charge of refrigerant just […]

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HVAC Capillary tubing

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Small-bore capillary tubing is used as a metering device. It is used on everything from the household refrigerator to the heat pump. Essentially, it is a carefully measured length of very small diameter tubing. It creates a predetermined pressure drop in the system. The capillary has no moving parts. Because a capillary tube cannot stop […]

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Thermostatic-expansion valve

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Thermostatic-expansion valve

The thermostatic-expansion valve, used primarily in commercial refrigeration and air-conditioning, is a refinement of the automatic-expansion valve (see Fig. 11-3). A bellows or diaphragm responds to pressure from a remote bulb charged with a substance similar to the refrigerant in the system. The bulb is attached to the suction line near the evaporator outlet. It […]

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Automatic-expansion valve

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Automatic-expansion valve

The automatic-expansion valve controls liquid flow by responding to the suction pressure of the unit acting on its diaphragm or bellows (see Fig. 11-2). When the valve opens, liquid refrigerant passes into the evaporator. The resulting increase in pressure in the evaporator closes the valve. Meanwhile, the compressor is pulling the gas away from the […]

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Hand-expansion valve

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Hand-expansion valve

Of the several types of metering devices. the hand-expansion valve is the simplest (see Fig. 11-1). Used only on manually controlled installations, the hand-expansion valve is merely a needle valve with a fine adjustment stem. When the machine is shut down, the hand-expansion valve must be closed to isolate the liquid line.

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