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-   -   Theremostat volt reading (https://www.askmehelpdesk.com/showthread.php?t=279877)

  • Nov 11, 2008, 06:33 PM
    chan025
    Theremostat volt reading
    Thank you HVAC1000. I took your advice and jumped the thermostat terminal from R and W. The heat had started. Right now, I replaced the thermostat but I have one question to ask you. When I set it to heat, after the furnace has been turned on, I checked on the PC board between C and W and I read only 2or3 volts. Isn't it suppose to be reading 24 volts because the heat is running?
  • Nov 11, 2008, 06:38 PM
    mygirlsdad77

    Curious
  • Nov 11, 2008, 09:01 PM
    hvac1000
    Isn't it suppose to be reading 24 volts because the heat is running?

    NO it will not read 24 volts since the circuit is already complete.

    You posted to a different location than your original post. Confusing to all of us. Post on the same thread as the original from now on. Glad you got it going.
  • Nov 12, 2008, 08:30 AM
    KISS

    Mmmm: R and W; V= ~0 when on
    ... C and W; V = 24 V when on

    Between C & R; 24 V all the time.

    There is a typo or misread. Between R & W is a contact and therefore it will read 0V when closed and likely 24V when open.

    Since W makes a connection to R, and between R and C there is a transformer, the voltage between C and W will read 24 V when the furnace is on and 0V when it is not.

    Furnace on should read call for heat.
  • Nov 12, 2008, 08:30 AM
    KISS

    Mmmm: R and W; V= ~0 when on
    ... C and W; V = 24 V when on

    Between C & R; 24 V all the time.

    There is a typo or misread. Between R & W is a contact and therefore it will read 0V when closed and likely 24V when open.

    Since W makes a connection to R, and between R and C there is a transformer, the voltage between C and W will read 24 V when the furnace is on and 0V when it is not.

    Furnace on should read call for heat.

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