Trane trg-trc005-en manual Condensers

notes

condenser is to flood the condenser coil with liquid refrigerant. A condenser coil tube that is filled with liquid refrigerant no longer acts as a condensing surface. Progressive flooding of the condenser coil tubes reduces the capacity of the condenser and raises the condensing pressure.

During normal, warm ambient conditions, valves B and C are open and valve A is closed. Assume that the system load is falling and, at the same time, the outdoor air temperatures has fallen to the point where the rate of heat rejection from the condenser balances the load at a condensing pressure less than desired. This minimum condensing pressure is the set point for valve A. As the condensing pressure decreases, so does the pressure in the discharge line. Valve B acts as a pressure regulator, and when the discharge-line pressure falls below its set point, valve B closes.

This causes the condensing pressure to drop farther. Sensing this reduction in condensing pressure, valve A opens and directs hot, high-pressure refrigerant vapor into the receiver. This increases the pressure in the receiver, controlling it to the desired condensing pressure. Because the pressure in the receiver is now higher than the pressure in the condenser, the check valve C does not allow the refrigerant to flow back into the condenser.

With valve B closed and valve A modulating to maintain the pressure in the receiver, the pressure in the discharge line begins to increase. When it exceeds the set point for valve B, the valve opens and again allows hot refrigerant vapor into the condenser. However, since the condensing pressure is still below the pressure in the receiver, the refrigerant cannot flow through valve C. This causes the condensed liquid to remain in the condenser, where it backs up, or floods, the condenser tubes.

The flooding of tubes causes the condenser to progressively lose capacity. When it has flooded enough that its capacity is reduced to the point where the condensing pressure rises above the pressure in the receiver, the higher- pressure condensed liquid will flow through check valve C into the receiver. This increases the pressure in the receiver above the minimum condensing pressure set point, closing valve A.

Condenser coil flooding provides the capacity modulation range needed to produce acceptable condensing pressures at reduced loads and correspondingly-low outdoor temperatures.