Trane TRG-TRC004-EN manual RQVWDQW9ROXPH6\VWHP

	period three
	The Compressor in a System
notes
	from the air used for space conditioning. In contrast, the refrigerant inside the
	evaporator of a direct-expansion (DX) system absorbs heat directly from the
	air used for space conditioning.
	The airside system responds to changing space loads by varying either the
	temperature or the quantity of air delivered to the conditioned space. A
	constant-volume system provides a constant quantity of variable-
	temperature air to maintain the desired conditions in a space. A variable-air-
	volume (VAV) system, however, maintains the desired space conditions by
	varying the quantity of constant-temperature air.
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Again, a constant-volume system supplies the same quantity of air to the space and varies the temperature of this air to respond to changing loads.

In this example single-zone, constant-volume DX system, in order to respond to changing space loads, the capacity of the compressor is controlled by directly sensing space temperature. The compressor is loaded or unloaded based on how close the actual space temperature is to the set point temperature.

Loading and unloading the compressor results in a temperature change of the air leaving the evaporator coil.

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