Certainly not normal. If your description of supply temps is accurate, it suggests your compressor is not operating at 50+ degree.

This should be monitored on your next heat wave. You can certainly hear the compressor running if you are outside next to condenser.

IMO

Checked and the compressor is running. Strange that the lack of heat only occurres only when the outside temp is 45 -50 or above. Has occurred several times at temperatures lower than those. Frost lines, defrost mode, aux heat all work fine. Tech that came out checked R22 and the pressures are ok.

30 minute cycles are very high I would go at least 60.

"Has occurred several times at temperatures lower than those."

Are you saying the problem is now occurring even when the temperature is below 45-50 degrees?

Could this be a symptom of a sticking reversing valve?

"Could this be a symptom of a sticking reversing valve?"

For mike,

Please elaborate on your statement...

One should not be getting a defrost call above 40 degrees...

IMO

What brand of system is it? Demand or time/temp defrost?

If you don't have any temp difference at grills above 50 degrees the compressor is either not running or not pumping. Is your indoor coil clean? Filter clean? If indoor airflow is obstructed it would cause pressure to go sky high when it is warmer outside( thus more heat to absorb) and the compressor pressure relief will pop and compressor will be running but not pumping.

Tigerdunes,

My thinking is the outdoor temperature drops below freezing at night which would require a defrost cycle and requiring the valve to reverse. On some cycles the valve could be partially stuck or leaking. I thought this might be a possibility given the OP describes it as an intermittent problem.

The tech that came out 2 weeks ago checked pressures and voltages and said no problems found. He did not look into the compressor compartment or check the evaporator coil in the flow line. Based upon the reply comments to my post, especially the one about "restricted air flow," I am going to have a different tech come out. Spoke with him this morning and he said to wait until outside temp is 50 or above so he can get better inspection results that may point to the problem. I have noticed that the volume of air out of the register(s) seems to be less than I remember. All inside filters are changed every two weeks to assure no restriction. Restricted air flow just may affect the line pressures. As to the problem below 45/50 degrees, I only remember this happening once or twice and it was right at the 45/50 temp point. Thanks to all. You are a really great bunch of specialists. After the tech visit, I will update as to his findings. May take a week or two. The label on the Heat Pump shows that it is made by International Comfort Products with Model # PHAD36N1K4.

James,
That package unit requires the top to be pulled to inspect evaporator coil.Also it is prone to mold growing in blower wheel and clogging it up, thus reducing airflow.
Hopefully this new tech can get to the bottom of your problem.

Follow up inspection by second technician revealed multiple problems that caused the compressor to overheat and shut down when temperatures were above 40 +/- degrees. Cost to repair would be very high due to using old R22 gas. Decided to replace with new 15 SEER, 3 Ton Maytag System. Warranty + the Supplier swayed me. Now installed and working great. One call back as installer forgot to put jumper in thermostat that calls for Aux heat. Other than that, very happy with system.