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Thread: Hiel H9mpd075

  1. #1

    Hiel H9mpd075

    I ran into a problem with a H9mpd075 furnace today that has me stumped. The burners ignite inside the burner tubes about .75 inches in front of the orifices, they burn there for about 30 seconds before jumping to the front of the burners where they belong. Furnace is on propane with an inlet pr. of 12 iwc, manifold pr 10 iwc. No adjustment of the manifold pr had any effect (tried from 6 iwc to 11 iwc). Anyone run into this before?

  2. #2
    Join Date
    Jul 2012
    Location
    Cincinnati ohio
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    252
    I've never seen that before. Is the inducer possibly not getting up to speed until after that 30seconds and not pulling the flame in?

  3. #3
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,470
    Very interesting. I had a furnace that wanted me to cut out some metal on the intake ports. this was in the manual.

    Have you tried unhooking the intake pipe or taking the burner box cover off to see if this would make it ignite properly?

  4. #4
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,470
    Maybe you have some cold fuel? Does the furnace have a drip leg piped into it?

  5. #5
    Has a new inducer assy. and the pr switch closes no problem.

  6. #6
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,470
    was the proper orifice used on the new inducer if it has one?

    I have seen pressure switches close when there wasn't enough pressure or not open when it became clogged with water. Have you verified pressure with a manometer?

  7. #7
    Join Date
    Feb 2008
    Location
    Altmar, New York, United States
    Posts
    5,113
    i have seen this but not all the burners. does it make a whistling noise? or any noise? did you see any soot when you changed the inducer? a semi plugged hx will do this. also i have seen it stop after a cleaning.

  8. #8
    The inducer for this furnace has the proper size inlet for the model. I checked to be sure the correct inducer was installed because each BTU size requires a specific inducer. Checked the burner orifice size, #55 correct for our altitude, there is a dripleg on the gas line, I disconected the combustion air pipe, no change.

  9. #9
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,470
    How many burners are effected?

    Are there any air shutters on the burners? Some models they want you to put a screw in each burner. Have you verified all the steps have been followed with the conversion?

  10. #10
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,470
    Have you put a manometer on the gas valve to see how it's opening. Maybe the valve is hanging up when it opens. This furnace does have the dumbvalve, correct?

  11. #11
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,470
    How old is the furnace?

    Put a combustion analyzer on it. I'm sure the furnace will tell you something then.

  12. #12
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    2,072
    Could there be a spider web in the manifold? I've seen some weird burner action (but just on individual burners) that had a spider web.

    I would check the draft, too. I've had some improper venting make burners do odd things.

    +1 for the combustion analyzer suggestion.

    I'm eager to hear what you find.

  13. #13
    Thanks for all your suggestions. So far the only thing I haven't tried is the combustion analyser, didn't have it in the van. Yes it does have the dumb valve, I hate those things. I'v replaced over 500 since they came out, and have seen them do some pretty strange things but never this. I watched the manifold pr when the valve opened and there was no fluctuation, steady 10 iwc from start till the flame jumped to its proper place. i'v pulled the orifices to check for blockage. I pulled the instructions for the propane kit and there is no mention of installing screws in the venturi and I have installed over 100 of the kits with no problems on any other furnace. Well I guess I'll beat my head against this wall tomarrow. Again thanks.

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