testing heat pumps

[Ron E. Perkerewicz]

recently saw where a realtor filed a claim against an inspector for testing a heat pump on a cold day and the colis froze up damaging the unit. any comments on when do you not test the AC, below 60 degrees ?

[Blaine Wiley]

You can test heat pumps down to just about as low as you want. The aren't real efficient as you go below 35 degrees or so, but they'll still run. The coils on a heat pump will frost over in certain weather conditions, and the unit should go into defrost mode. If the coils were frozen over, it indicates a problem with the unit, and should have been written up.

Unless you're properly trained, don't test the A/C below 60 degrees.

[David A. Andersen]

A heat pump is not an "air conditioner" which is subject to the 60° standard.

A heat pump has a crankcase heater on the compressor to keep refrigerant from entering the oil.
A heat pump has an accumulator which prevents refrigerant in a liquid state from entering the compressor during the low ambient conditions. This device also prevents oil, which may have pumped out of the compressor at start up from returning in a large quantity back to the compressor causing compressor failure.

The only damage I have seen to coils due to ice was a distortion effect on the bottom of the outdoor coil where ice was not adequately defrosted due to an improper adjustment in the the defrost termination thermostat. No permanent damage occurred other than a small amount of potential reduced capacity due to restricted airflow through the bent fins.

That story/claim sounds very bogus to me.

[Ed Figueroa]

Normally for heat pumps, if it works one way it will work the other way. Rule of thumb...test heat in temps below 60, and cold in above 60.

[David A. Andersen]

Normally for heat pumps, if it works one way it will work the other way.

I would be somewhat reserved about making that statement in this business.

Heat pumps are very complex machines. No home inspector is going to fully test a heat pump in the heating mode during a home inspection.

Seeing someone asked, these are the basic steps to test a heat pump in the winter (actual performance of this test is much more complex) .

1. Disable the heating elements for the auxiliary heat.
2. Turn on the thermostat and evaluate the heating performance of the heat pump refrigerant circuit.
3. Disable the outdoor fan while the heat pump is running to cause the outdoor coil to frost over.
4. Jump the terminals at the defrost thermostat sensor.
5. Accelerate the time clock on the defrost circuit board until the unit initiates the defrost cycle.
6. Ohm out the defrost termination sensor and insure there is continuity. If not, run the unit without the outdoor fan longer until the sensor closes.
7. Reinstall the defrost thermostat termination sensor to the circuit board. Initiate a defrost cycle and insure the defrost termination sensor takes the unit out of defrost when the ice is gone from the out door coil.
8. Place the thermostat in the emergency/auxiliary heat mode and insure that all heating banks energize in sequence.

In the scenario of this thread it is highly likely that the heating system was not operating properly at the time of inspection. However, due to the scope of home inspection and the required licensing and certification by the EPA this evaluation would/could not be performed during a standard home inspection.

The reason for the alleged damage due to icing of the coils is likely the result of one of the defrosting components not performing as intended. An HVAC specialist is the only one in this scenario that could be responsible for an inspection and alleged damage to the equipment.

Rule of thumb...Don't use rules of thumb...