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  1. #1
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    Nov 2014
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    Pilot tube gas pressure

    I was working on an old rheem unit today with literally no numbers or manuals in it. This is a gas unit and the pilot tube is not lighting. The spark looks good but will not light. The inlet gas pressure is the same as the pilot pressure (7.5”). Shouldnt pilot pressure be closer to manifold pressure (3.5”). I’m unsure if this varies unit to unit though i havent had many issues with pilot tubes in my career.

  2. #2
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    Oct 2011
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    Pilot is equal to inlet unless otherwise specified.
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  3. #3
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    Jun 2011
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    Quote Originally Posted by Bglenn525 View Post
    I was working on an old rheem unit today with literally no numbers or manuals in it. This is a gas unit and the pilot tube is not lighting. The spark looks good but will not light. The inlet gas pressure is the same as the pilot pressure (7.5”). Shouldnt pilot pressure be closer to manifold pressure (3.5”). I’m unsure if this varies unit to unit though i havent had many issues with pilot tubes in my career.
    is this a " light off tube " that extends across the burners with tiny holes on the burner side ? possible the tiny holes are rusted close, that will prevent the light off tube from lighting ..... you can buy another light off tube, or clean out each hole using a small strand from a piece of copper stranded wire or something else ..... not sure what pressure those operate at ...... also, spark alignment is somewhat critical .....

  4. #4
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    Nov 2014
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    Thread Starter
    Quote Originally Posted by hvacskills View Post
    is this a " light off tube " that extends across the burners with tiny holes on the burner side ? possible the tiny holes are rusted close, that will prevent the light off tube from lighting ..... you can buy another light off tube, or clean out each hole using a small strand from a piece of copper stranded wire or something else ..... not sure what pressure those operate at ...... also, spark alignment is somewhat critical .....
    The spark ignitor is mounted to a plate with 2 screw holes so you cant really move the sparker. That was my thought also but it looks like it’s sparking at a good spot. I’ll pull the tube and try to clean it out. Thanks

  5. #5
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    Aug 2015
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    Buffalo,NY
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    So you have electronic ignition but it sounds like you have a true pilot burner? Dose it light with a match? I’m guessing the office in the pilot burner is plugged. Just take it apart and clean the office. Also on the gas valve by the pilot tube usually there is a screw head. If you take that out under should be a small flat head screw. That’s your pilot adjustment. If you have gas coming out of the valve for ignition your problem is between the valve and pilot burner.

    Now if you have a spreader bar, which is an aluminum tube with holes ontop for gas to come out that could be dirty preventing gas from weeping out to fire off. Also usually there is a mixer on there with an orfice as well.

    Have you verified you have a good spark and or ground for the spark? A strong spark with enough room for that hot spark to jump and fire off?




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  6. #6
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    May 2004
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    Quote Originally Posted by Bglenn525 View Post
    I was working on an old rheem unit today with literally no numbers or manuals in it. This is a gas unit and the pilot tube is not lighting. The spark looks good but will not light. The inlet gas pressure is the same as the pilot pressure (7.5”). Shouldnt pilot pressure be closer to manifold pressure (3.5”). I’m unsure if this varies unit to unit though i havent had many issues with pilot tubes in my career.
    As stated pilot pressure can be what ever inlet pressure is. The pilot adjustment is not a regulator, only a needle valve. Look for spider webs or any bugs making a home.

  7. #7
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    Nov 2014
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    Thread Starter
    Quote Originally Posted by hvacskills View Post
    is this a " light off tube " that extends across the burners with tiny holes on the burner side ? possible the tiny holes are rusted close, that will prevent the light off tube from lighting ..... you can buy another light off tube, or clean out each hole using a small strand from a piece of copper stranded wire or something else ..... not sure what pressure those operate at ...... also, spark alignment is somewhat critical .....
    Went back today and cleaned out the holes with a peice of stranded copper wire. Lit up like it was new. Posts like this is why i love this website haha...thanks man

  8. #8
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    Jun 2011
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    Quote Originally Posted by Bglenn525 View Post
    Went back today and cleaned out the holes with a peice of stranded copper wire. Lit up like it was new. Posts like this is why i love this website haha...thanks man

    cool, glad that worked, as another poster mentioned sometimes you can come across cob-webs blocking the tube ..... another thing you might want to keep an eye on with an older unit like that is the light off tube / burner ground, as the unit ages sometimes you will lose your ground to the light off tube / burner and the ignition control wont sense the light off tube / burner flame, so keep an eye on all of your ground connections .... what I have done, and even with units just a few years old as a preventative measure, is run a ground wire ( 16 gauge, 14 gauge ) directly from the light off tube / burner to the ignition control ground wire ......

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