Seems my new millvolt gas valve turns off PILOT and MAIN BURNERS?

Discussion in 'HVAC Heating & Cooling' started by mnalep, Oct 12, 2015.

  1. mnalep

    mnalep Member

    Joined:
    Apr 29, 2008
    Location:
    Redford, Michigan
    I have a problem with the new combination (White Rodgers 36C03U-433) valve that I just bought and installed on my milllivolt (thermopile generator) on Luxaire SH-125 gas furnace.

    The old valve had a pilot line that was fed off of a separate gas cock mounted just before the main gas cock valve.

    This is different from the new installed WhiteRodgers 36C03U-433 valve where the pilot line feeds out of, and is controlled by, the new combination valve. Could this be the reason the pilot goes out on high LIMIT - it is no longer independant of the combination valve control unit?

    The new valve seems to work fine up until the point where the limit switch is tripped - and at that event the combination valve 'clunks' and main burners close - and the pilot flame goes out. So at that point the furnace is no longer operational unless I manually relight the Pilot.

    The millivolts reading was 400 Mv on my new combination valve at the TH-PG and PG terminal screws with only the Pilot on. It drops to about 375 Mv when the burners come on.

    When the LIMIT activates and turns the main burners off, the millivolts readings immediately drop, and the main burners AND THE PILOT flame both go off. (That is how I knew the pilot went out at that moment - the millivolts sudden drop and observation that pilot was out.)

    Could I have a faulty gas valve (even though it's brand new)?

    The Thermopile generates 400 MV while connected to the combination valve. I think that is adequate?

    I am really stumped. I can even turn the gas cock on the combination valve off, and on, several times, and the PILOT stays lit while the burners go off and on. The PILOT stays lit when the main burners fire up, and when the blower motor comes on.

    It seems wrong that the LIMIT switch should turn off the main burners and the PILOT FLAME! Seems the Pilot Flame should continue to be fed gas even after the main burners shut off.

    Is my new gas valve (White Rodgers 36C03U-433) not compatible?

    My old valve was a Honeywell VS87A9X4X2, for the thermopile generator pilot.

    Thanks, Matt
     

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  2. mnalep

    mnalep Member

    Joined:
    Apr 29, 2008
    Location:
    Redford, Michigan
    Old valve chain pictures
     

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  4. mnalep

    mnalep Member

    Joined:
    Apr 29, 2008
    Location:
    Redford, Michigan
    New valve installed picture:
     

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  5. Tom Sawyer

    Tom Sawyer In the Trades

    Joined:
    Nov 29, 2010
    Location:
    Maine
    Incompatible gas valve
     
  6. mnalep

    mnalep Member

    Joined:
    Apr 29, 2008
    Location:
    Redford, Michigan
    Hi Tom,

    I just asked the seller, and they say the thermopile needs replacing. They say 400Mv is too low to hold pilot open when the limit shuts down the burners, nand need to be 700-750Mv even while attached to the gas combination valve.

    Then, the person at WhiteRodgers says the limit shuts off the main and pilot burners. If so, how does the pilot ever get relit? (except by a human, that is)
     
  7. Tom Sawyer

    Tom Sawyer In the Trades

    Joined:
    Nov 29, 2010
    Location:
    Maine
    It's the wrong gas valve. Made for HSI. You need to use like a honeywell VR800
     
  8. mnalep

    mnalep Member

    Joined:
    Apr 29, 2008
    Location:
    Redford, Michigan
    I just googled that VR800. That is for a 24V system. Mine is a millivolt system with Pilot Generator (Thermopile).

    I was just re-reading the installation sheet that came with the valve. It does show how to hook up the 36C03U-433 with a pilot generator and limit for 750 Millivot system. But I just notice something I missed when I order this combination gas valve.

    The instructions sheet specifies that the 36C03U is for use with:
    STANDING PILOT = YES, but,
    PROVEN/INTERMITTENT PILOT = NO.

    It seems to me that the STANDING PILOT was the way m old Gas chain was installed (with a separate gas cock for the PILOT FLAME in front of the gas valve unit.

    Also seems that the way the instructions have me installing the PILOT LINE into the COMBINATION GAS VAVLE itself would be what they are calling PROVEN/INTERMITTENT pilot? (IF so, the 36c03U seems to require the STANDING PILOT line hooked into the PILOT GAS COCK - as the valve does not support the Proven PILOT whic h I think is that he thermopile is doing - proving the pilot ased on millvolt readings?).

    This I could do but I'd have to ensure the PILOT outlet from the 36C03U must b completely sealed off. I was thinking I could turn the PILOT ADJUSTMENT screw all the way down to basically close the PILOT outlet on the valve. I was then wondering if there is available a break-away compression fitting that is a cap for the pilot outlet(for a secondary measure of safety to prevent all pilot gas from leaving the combination valve.

    What do you think - is shutting down the PILOT output like this possible, while using the stand alone pilot gas cock?

    Here is a link to the installation sheets the 36c03U Combinatin valve:
    http://www.emersonclimate.com/Documents/White-Rodgers/instruction_sheets/0037-7349.pdf
     
  9. largewon62

    largewon62 New Member

    Joined:
    Jan 3, 2016
    Location:
    Chesapeake, Virginia
    I know this is an old thread, but you cannot use just any valve, you must use the one the manufacturer calls for.
    Also, you need to figure out why the high limit keeps kicking off. You may kill your family.
     
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