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heat pump wiring

Had a split system one stage carrier heat pump which didnt have 24 volts feeding defrost boatd. I had no 24 vlt to unit on y &c. Had r&c 24 vlt and if I put the r&c to board it kicked over condenser. I picked up a spare wire and jumped r to the new wire which now was going to be y.wire.i measured 24 volt between this nee wire and c but wouldnt pull any thing in. Is this a false reading, ground reading or something? 24 volts to r&c which had same reading pullef board in. What the heck is that reading of 24 volts and not working. I suspect bad wires as problem but why the fake reading. Tstat is new, but I was jumping terminals at tstat to be sure while doing tests. New tstat , good controls in condenser, 24 vlt trans working and new tsat. What is up?


  • wogpa67
    wogpa67 Member Posts: 238
    The defrost board needs a constant 24v. Doesn't matter what brand. Once it loses the 24v you are on the timer.
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    If you put current in one end of a wire and it doesn't come out the other end, the wire is broken.

    R & C should be energized all the time. R being 24v ac hot and C being 24v ac common. The thermostat connects the R terminal to whatever terminal meets the requirement for the current call. In the case of a call in heat pump mode, it would normally complete the circuit to the Y, G, In cooling the norm would be the Y, O, G
  • Paul_69
    Paul_69 Member Posts: 251
    Thx.what about the 24 volt reading that did nothing even though my meter read 24 volts. On y&c.and 24 vlts on r&c would pull in unit if I temporally moved to see if would pull in contactor
  • Jamie Hall
    Jamie Hall Member Posts: 22,114
    On that meter reading -- keep in mind that your meter has a very high resistance -- probably several megohms or more. It might read 24 volts, but if you put any real load on the circuit and there is resistance in the circuit, you'll see a drop to very low voltage. Try measuring the voltage with a load -- such as the unit.

    Could be a bad wire, bad connection, bad source.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • unclejohn
    unclejohn Member Posts: 1,833
    It's a bad wire. Pull a new 8 wire out to the condenser. Think of the 24v you are reading as ghost voltage, it's there until work needs to be done. Like pull in a contactor then it goes away.