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Heil / Honeywell "smartvalve" gas furnace issue

prc_2 Member Posts: 2
The culprit: Heil propane furnace (H 9MPD1 series) with Honeywell SV9451 smart valve, running on LPG

First problem: no pilot produce during ignition cycle. I took the tube to the pilot off, and carefully cleaned the jet (in the past, speck of rust or corrosion have blocked it, and caused a similar problem). This didn’t work. Next step was to adjust the pilot flame using the set screw. At this point, I got a nice, steady pilot, and the furnace came on as expected. I watched it over the next few cycles just to make sure everything was OK, and then noticed a different problem.

The problem now is that on some cycles, especially when the furnace is starting up after not running for a number of hours, only three of the four main burners ignite. Doesn’t happen everytime - when I see this, I shut down immediately, wait minute, and then start up again, and typically all four burners then ignite. The one that fails is the one farthest from the valve, at the end of the gas feed pipe. When it does ignite, it produces a strong blue flame just like the other three.

Any ideas?


  • Tinman
    Tinman Member Posts: 2,804
    Incoming gas pressure and manifold pressure need to be checked. Are you certain you were adjusting just the pilot pressure?
    Steve Minnich
    JUGHNE Member Posts: 10,572
    I would second the gas pressure issue.
    Sometimes the LP supplier will service the regulators. You probably have one at the tank and one at the house.

    If you had to adjust the pilot flame to be higher, then the incoming pressure may be down. If so, when corrected, the pilot would need readjustment.
  • prc_2
    prc_2 Member Posts: 2
    Thanks for the good suggestions. I think I found and solved the problem without the manometer.
    I took the burner out, and noted that the thin spaces between the flanges that connect the burners were choked with scaly rust. I scraped them clean, blew them out, and have not had any additional problems.
    Will replace the burner and check gas pressure then.
  • SuperTech
    SuperTech Member Posts: 1,919
    Definitely check the gas pressure. Also make sure the furnace is vented correctly and draining correctly if it's a 90+ efficiency. Rust build up on the burners is definitely not normal and something is causing it. If it isn't forced draft check the draft using the same manometer. If it does have a draft inducer check the wheel and make sure it isn't rusty or restricted in any way.

    No matter what make sure you have a good Carbon monoxide detector!