weird thermostat voltage issue

Discussion in 'General Electronics Chat' started by tkeoki, Oct 10, 2009.

  1. tkeoki

    Thread Starter New Member

    Oct 10, 2009
    2
    0
    I'm trying to figure out an issue on a thermostat connected to a zone control board that's connected to a Water Source Heat Pump. See attached wiring diagram.

    Existing thermostat(White Rabbit TP32W02) works on any connector: Unit, P9, P1, P2, P3 or P4. The new thermostats (3 of them--Diversitech PS32H) only work when connected to Unit or P9. However when connected to P1 - P4, the circuits Y1, Y2, Y3, O, W and G are energized the second the wire is connected, even though the thermostat is off.

    For example, I verify that the thermostat is off and a reading of 0 volts between C and G. if I connect R, C, and G, The measured voltage between R & C is 25.3 volts, and between C and G is 3 volts??(enough to energize the circuit and turn the fan on). If I turn the fan on at the thermostat, the voltage between C and G changes to 25 volts.

    I've removed the wiring out of the equation by using a short 3 ft section.

    I'm not sure where this 3 volts is coming from on the circuits that are supposed to be off. Any other measurements you'd need me to take to help troubleshoot this? Thanks.

    *all voltage is A/C

    Thomas
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    I can't seem to see the thermostats, or SW3 on your diagram?
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    395
    I think is upper left on zone 1??
     
  4. tkeoki

    Thread Starter New Member

    Oct 10, 2009
    2
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    Yup, its the top left with h(24v), c(common) and g(fan) wired.
     
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