Trane trg-trc005-en manual Condensing Temperature Control

period two

Condensers

notes

A reduction in condensing pressure lessens the power required to compress the refrigerant. Unfortunately, if the condensing pressure falls too low, the expansion valve may not be able to produce the flow of liquid refrigerant needed to satisfy the demand at the evaporator. In some systems, as the condensing pressure drops, the compressor suction pressure also drops, resulting in evaporator frosting and possible compressor shutdown due to a low-pressure safety device.

While it is not essential to control condensing pressure to a constant value, provisions should be made to control it within acceptable limits.

Condensing Temperature Control

flow-regulating valve

condenser

condenser water pump

Figure 17

One common method of controlling the capacity of a water-cooled condenser is to vary the rate at which water flows through the condenser.

For example, assume a water-cooled condenser is piped to a municipal water system. To control the capacity of the condenser, a flow-regulating valve is installed on the leaving-water side of the condenser. As the load on the system decreases, the regulating valve senses the lowering condensing pressure. The valve reduces the flow rate of the water until the heat-rejection rate of the condenser balances the system load at an acceptable pressure and temperature.

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