I am working on a R22 Lennox Split Heat Pump 3 ½ ton. The unit will trip on the compressor relief valve in heating. I was unable to test the unit S/C and S/H accurately, due to the High Side pressure building up so fast with in a minuet will be hitting 400psi and blow the low side would sit at about 50psi. I tested the RVR from cooling to heating, and even tested the unit in cooling for a bit, pressures were ok. When in cooling my high side was 135 and low 50psi with an outdoor temp of 45degres and indoor temp of 75 degrees. I then switch back to heating and the same problem would occur. I have good air flow and in cooling the spilt seemed to be acceptable. The only other issue to mention, was when I arrived the customer stated that this summer they had a service company repair a pin hole leak somewhere in the system. I looked all over the coil, could not see any repair, or where they made the repair. I also did not see a new filter dryer installed, only the old one still in the system. I am puzzled the unit seems ok in cooling, the SH in cooling about 8 degrees, could the RV be not setting all the way in heating, or is there an issue with the TXV, with the possibility of recent sealed system work, I have a concern that there may be a restriction.
Any Ideas? Happy New Year