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  1. #1
    Join Date
    Feb 2010
    Location
    Milwaukee, WI
    Posts
    62

    Main burner blowing out pilot

    Need help working on a Residential climatrol furnace. I forgot the model #. I just installed a universal 24v gas valve and new thermocouple the other day. I got a call back today. Tenant complaint of no heat. I went to check it out again and the pilot went out. I relighted it. I checked the gas pressure and it was reading at 3.5 wc. During the 8 or 9 cycle the main burner would puff back and blow out the pilot. I can't figure out what to do the problem. A little help would be nice.

  2. #2
    Join Date
    Feb 2010
    Location
    Ontario Canada
    Posts
    1,339
    You need a slow opening valve, or a step opening valve...I do not know what you call them down there.
    Never give up; Never surrender!

  3. #3
    Join Date
    Dec 2010
    Location
    Toronto
    Posts
    1,253
    Are you reading 3.5" at the inlet to the valve while running? If so, you should probably have 4.5" minimum for the valve to work properly. It needs a pressure differential to operate the diaphram properly.

  4. #4
    Join Date
    Feb 2010
    Location
    Milwaukee, WI
    Posts
    62
    So I have to get a slow opening valve? I'll look into it.

    Yes, I am reading 3.5 at manifold. I haven't check the inlet yet. So you are saying I might not have enough gas pressure?

  5. #5
    Join Date
    Aug 2011
    Location
    Ontario
    Posts
    379
    Check heat exchanger & venting for blockage. But most likely not a slow opening valve.
    There is no bad beer, some just taste better than others.

  6. #6
    Join Date
    Dec 2010
    Location
    Toronto
    Posts
    1,253
    Quote Originally Posted by xxcels View Post
    So I have to get a slow opening valve? I'll look into it.

    Yes, I am reading 3.5 at manifold. I haven't check the inlet yet. So you are saying I might not have enough gas pressure?
    I've seen it before where too low of a line pressure, which can be due to the utility meter, doesn't allow the appliance reg to work properly in the way you are describing.

  7. #7
    Join Date
    Nov 2011
    Location
    Charleston, Wv.
    Posts
    1,269
    I've always considered the minimum inlet pressure to be 7"wc.

    what's the make/model? should specify if it needs a step valve. If it doesn't you may have a flu blockage.

  8. #8
    Join Date
    Dec 2006
    Location
    Litchfield,Il
    Posts
    565
    I also think you may have a flue restriction. You also have a good strong pilot right? just asking. is this propane? if so the pilot has to be clean 1st thing.
    If your not getting the results you desire then change. People change from either desperation or inspiration.

  9. #9
    Join Date
    Feb 2012
    Location
    Alabama
    Posts
    378
    Quote Originally Posted by SolarMike View Post
    I've seen it before where too low of a line pressure, which can be due to the utility meter, doesn't allow the appliance reg to work properly in the way you are describing.
    +1

  10. #10
    Join Date
    Feb 2012
    Location
    Virginia
    Posts
    34
    First thing of course is to be sure you have a strong enough pilot flame. Second, is there any flame blowback or rollout when the burners ignite? Third, did this happen before you replaced the gas valve?

  11. #11
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    6,914
    If this is a natural draft furnace with an open hood, a blocked flue will have no effect on the burner.

    Is the pilot getting blown out, or is the pilot valve closing due to insufficient DC milivoltage?

    Make sure the pilot flame is sharp and completely engulfs the thermocouple. Measure the dc milivolts.

    If the thermocouple is just barely holding the valve open, the flame only has to flutter away from the t-couple for a couple seconds to drop out the valve.

    If it is indeed blowing it out, check for a restricted heat exchanger and if its ok install a slow opening valve.

  12. #12
    Join Date
    Feb 2010
    Location
    Milwaukee, WI
    Posts
    62
    Quote Originally Posted by JPJ13 View Post
    First thing of course is to be sure you have a strong enough pilot flame. Second, is there any flame blowback or rollout when the burners ignite? Third, did this happen before you replaced the gas valve?
    There seem to but no Data plate on the unit but the cover of the manual

    M# 174-0 Series
    Gas furnace

    Yes, I checked the pilot and there is a strong pilot flame. I putted a new thermocouple there too, measuring at 25mv.

    I lowered the manifold pressure to 3.0" wc but still the problem persist

    This is a natural draft furnace and I checked the flue vent and it seem to be clear. The heat exchanger look clear to me but I will have to double check when I go back. I didn't bring my tools with me.

    I went to double check it today and I have a flame blowback when the main fired up. It will not do this all the time but 1 of 5 tries and it would blow out the pilot.

  13. #13
    Join Date
    Feb 2012
    Location
    Virginia
    Posts
    34
    Burner blowback or rollout upon startup should have nothing to do with the type or style of gas valve. Typically on that style of furnace you are going to have clogged burner ports or dirty heat exchangers. Here is another thought, the times when you have flame rollout, is the blower motor already on during that ignition?

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