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Three Zone Oil Furnace Short Cycles On One Zone

lghdoclghdoc Member Posts: 2
I have a three zone forced water oil heating system. When the bedroom zone calls for heat, the furnace short cycles repeatedly. The other two zones work normally, independently and together. The issue is only when the bedroom calls for heat by itself or with one or both of the other zones. The Honeywell thermostat anticipators are set for longer cycling. I swapped thermostats and valve heads and the issue stays with the bedroom zone. I also swapped the valve heads and kept the wires in place so that the living room thermostat would control the bedroom zone and short cycling continued. When doing so, I verified the bedroom zone valve was the zone calling for heat by turning the other thermostats off, and I was able to pull the valve lever down on the affected zone. Hot water is flowing through the bedroom zone pipe but again it short cycles, so the bedroom doesn't get enough heat. Please advise. Thank you


  • HVACNUTHVACNUT Member Posts: 3,349
    Just so we're clear, the burner short cycles?
    You have to manually open the zone valve to get heat to the problem (bedroom) zone?
    Controlling the zone valve for the bedroom from another thermostat swapping heads and having it still short cycle doesn't really make sense.

    It's not the thermostat because you swapped it.

    It's not the head because you swapped it.

    It's not the control wiring because because you've tried wiring the bedroom zone valve to a known (living room) working circuit and it (the burner?) still short cycles.

    That you had to manually open the zone valve is a little perplexing.

    To get heat for now, you can turn the bedroom thermostat off, manually open the bedroom zone valve, and you'll get heat in the bedroom anytime another zone calls.

    Do you have an electrical meter to check ohms?

    Can you post some pics of the boiler and zone valves?
  • GBartGBart Member Posts: 753
    Timing of the short cycle and is it the burner going on off?, is it a few minutes, few seconds, short cycling is a vague term
  • lghdoclghdoc Member Posts: 2
    edited October 2018
    Thanks for your response. Short cycle time was a few seconds. I didn't have to manually open the valve, I did so to verify that it was the only zone calling for heat, and to check that the lever moved easily confirming the valve was open. However the issue is resolved and the cause was simply air in the affected zone. I drained water and air from the zone with instructions from Youtube In hindsight, hearing the water gurgle as it entered the baseboard pipe was apparently a clue, though I didn't realize air in the system could cause this issue. Thanks again
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