Defrost Icing Problems - American Standard Heat Pump

by adam kiger
(kernersville nc)

This unit is an American Standard heat pump, 2.5 ton 13 seer, R-22. It ices up every time it is 42 degrees or colder and raining outside. The refrigerant charge is good with 10 degrees F of superheat. It also has new board and heat pump defrost sensor on it. I think the rain freezes on top of the unit but they always cut it off before I get there. I have noticed that there are a lot of these American Standards that are operating like this this year. But mainly this one is having the most problems. It does have an 10 year older Trane air handling unit on it.

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Mar 29, 2013
Sounds like an American Standard problem
by: Anonymous

If many American Standard heat pumps are doing this, it may be a design flaw. Have you tried contacting American Standard regarding this problem?

It sounds like the rainwater is freezing as it moves across the evaporator coil. At 42 F the evaporator temperature must be at or below freezing in order to meet the load. The heating season should be over soon, but in the meantime if you can't find a solution, is there a way that you can put up a temporary rain shield. This would give the heat pump a few more degrees before freezing becomes an issue.

Of course you need a permanent solution.

Does the defrost try to come on?

Is there auxiliary heat available in the building? If so, can it be controlled to turn on sooner?

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