RUUD Heat Pump Tripping on overpressure

I had a RUUD UPKA-030JAZ that had a rust leak in the accumulator that released all of the freon. It ran several days before we discovered the problem. I am sure that it overheated the oil in the compressor.


We found someone who would replace the accumulator, instead of selling us a new $4800 system. They did a very good job & it worked great until winter, when we started getting frequent tripping of the overpressure switch. This unit requires switching the reversing valve for heating. I suspected that the overheated oil had gummed up the valve and it was switching slowly, producing a momentary pressure spike. As my unit is controlled by a PLC, I had the unique opportunity to prove my hypothesis. I put a time delay so that the compressor would not start until a second after the valve shifted. The tripping ALMOST stopped.

Determining the exact pattern of the remaining tripping was much more difficult. I finally realized that it only tripped when the temperature was as hot as possible to still require heat (i.e. 50s or 60s). It did not trip AT ALL when the temperature was very cold (I allow it to run down to 30 degrees).

I determined that it only tripped during the defrost cycle, since this is the only time that I do not have control over the timing of valve and compressor. BECAUSE it did not trip at lower temperatures when defrost cycles were much more frequent, the pressure had to be just marginally too high (the pressure is higher at higher ambient temperature).

The average serviceman will not tell you this, and may not even know this.  It is worth the effort to convince them, even if it costs another service call, if it saves you $4800!

I got the serviceman who originally replaced the accumulator to 1) install Supco oil treatment which is a Teflon additive, and 2) lower the pressure slightly. I have had no further problems and expect to get many more years of service!