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Waterfurnace geothermal high pressure lockout

kygeo Member Posts: 2
I received a high pressure lockout on my unit. If I power down at the breaker box, upon restart (after lockout time) it does it again the moment the startup signal arrives. So the blower starts but nothing else. Usually the loop pump and condenser wouldnt even try to start for another minute or two, so it seems to fast for it to detect a flow problem. I haven't had refrigerant added in the 11 years I've been here... So that shouldn't be too high either. Thoughts????


    JUGHNE Member Posts: 8,650
    I had a similar problem on a water to air HP. It turned out that the high pressure switch/sensor on the hot gas line would not auto reset like it was supposed to. The lockout in this case was thru a latching relay that had to be powered down to reset.
    With power off you can test that HPCO with a meter. With no abnormal pressure conditions it should be closed.

    If I recall the solution was several good whacks with the rubber handle of a screwdriver. The internal mechanism did reset itself and this avoided replacing the pressure sensor. You just have know where to hit it........hi tech repair ;)
  • BobC
    BobC Member Posts: 5,208
    In the old days we would take the cover off the relay (or contacts) and use a clean dollar bill to burnish the contacts

    The old tombstone thermostat (late 30's ?) in my apartment had to be burnished yearly until I replaced it with a round honeywell with mercury bulb.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
    JUGHNE Member Posts: 8,650
    The contacts I refer to are the internal switch of the HPCO which is soldered into the hot gas line of the compressor. They are hermetically sealed as part of the refrigeration system and are a NC contact.

    The case I had was where the switch was stuck open after a hi limit event and would not reset internally. It was either recover R-22, open system, replace HPCO, flow N2 gas, evacuate, and recharge.

    It was a stroke of luck that the wracking released it back to NC position.
  • pecmsg
    pecmsg Member Posts: 2,200
    Pinch off tool, cut out bad control, Braze in new control, open tubing.

  • JStar
    JStar Member Posts: 2,752
    We'll need to see pressures and temperatures to make any accurate diagnosis.
  • kygeo
    kygeo Member Posts: 2

    Convinced that the high pressure light was wrong (system was cool and it was kicking on immediately), I shorted the switch. Everything came, except the Grundfos loop pump... ok, so maybe the high pressure light was "predicting" that state because it didn't receive a water flow signal within the half second of startup? So.... I took the pump power off the control board and wired it directly. Pump came on; so it is working. So maybe it just wasn't receiving the signal to turn on. Turn unit on... high pressure light still comes up and shuts it down. So I shorted the high pressure switch again (ground loop pump still running while wired separately). Voila... I have cooling. Everything is going great. The compressor discharge line is not very hot (115F), so I feel comfortable I don't have a high pressure issue. After about 3 hours of cooling the house successfully, all of a sudden the vents start blowing hot air (100F) instead of 63F. Hmmmm.... I go check and the ground loop from the unit is still several degrees warmer than the inlet. The coil surface is 40F. The compressor discharge is still 115F. Everything looking good.... so I check the auxilliary heat and it is on. So I'm heating my cooled air. Now.... a day later, I've been running cold air with three fixes: ground loop wire on permanently, high pressure switch shorted, and auxilliary heat unplugged. Any thoughts on why these three things would happen at once???

    JUGHNE Member Posts: 8,650
    edited August 2015
    Have you put a set of gauges on this. If you don't have any or are not familiar with the refrigeration cycle I would suggest calling a pro.

    I would never leave the high pressure switch shorted for any length of time at all without watching the actual head pressure on a gauge.

    A compressor in a geo heat pump is a pretty big ticket item to leave to chance. If they fail the route is to quite often replace the entire unit. :o IMHO

    Also a 115* line sounds like a liquid line temp. The compressor discharge line is hot enough that you will know when you find it.
    (Unless something has changed in AC/HP compressors lately, usually you spit on it and it is sizzling.)

    If you can't find the hot gas line, I would suggest calling a pro you know.

    IT sounds like you have a major control board issue. But without knowing pressures everything is a guess.