CHICAGO — Four-way reversing valves are at the heart of heat pump systems, and are indeed necessary to their function. An ASHRAE technical committee is looking for input as to how much capacity is lost through their operation, and how it should be tested.

The forum, “Are Internal Leakage and Heat Transfer Required in a Standard for Method of Testing for Capacity of Four-Way Reversing Valves,” asked these “essential” questions:

  • What are the causes of the leakage?
  • How important is it?
  • Is it significant?

It was pointed out that in the action of a four-way valve, the slide moves away from the ports in either the low- or high-pressure streams. “They interfere with each other,” an engineer stated, resulting in a loss of both heat and mass transfer.

“You lose mass flow and reduce suction pressure drop.” This, in turn, affects the efficiency and capacity of the compressor.