Delayed ignition IBC dc20-125 propane
Happy St Paddy’s Day!
Service tech, licensed 3yrs. I can be long-winded, so I’m gonna try to leave out the filler. Service call for no heat, 11 on the board. Ended up finding the supply sensor shorted due to high heat exposure. Signs of heat damage inside boiler cabinet on exhaust pipe and insulation on upper left. Found the upper left side bolt loose and the gasket sealing the front plate to the heat exchanger was heavily damaged. It was deemed that at bare minimum, a front plate kit (due to warped aluminum face) and temp sensor would be needed. Got those and installed earlier today…
…boiler would go through its sequence of operation but no ignition. Got tech support on the line. I did swap out the regulator at the tank after the pressure drop was deemed excessive (start @11” then would drop to 8.5-9” during trial for ignition) After reg swap, 11.5” with drop to10.5” tfi. Still no ignition. Ended up pulling igniter, PitA, warming with a torch and bending it away from the burner. Now I have ignition! Yay!
I had the thermostat turned up and had heat on return relatively quick, small house. Open a tap, boiler kicks up and soon had hot water at the tap. Close the tap and boiler heads into post-purge. Everything seems grand. This entire process was less than 10min, from first successful ignition to ending call for domestic. The thermostat is still up and zone board is still calling so whatever the delay time was, like 15sec?, the boiler then cycles to fire. This is where it got sketchy and why I’m posting here now.
I’m 10ft from the boiler and it sounds like a gun goes off. This happens 2 more times before I can get my wits and turn the thing off. I’ve experienced delayed ignition before but this one was different. Definitely shook me up a bit.
Had tech support back on the line. I have a new burner kit and igniter coming overnight.
The front plate kit included: burner gasket, burner screws and o-rings, ground spring, fan gasket, inlet gas valve o-ring, new conversion “hood?” and flapper, the front plate with gasket and mounting bolts. Installed all that. Put in the new supply sensor.
The second call with T.S. they stated that the burner may be loose prompting the funky ignition. I pulled everything apart, the burner itself was snug and the new gasket was in place. The burner mesh did have some bubbles, like old loose skin or maybe an air bubble behind an amateur level paint job…could this really be the cause of my near soiling myself event?
My service manager came out and brought a new igniter. But it had the same effect as the old before I bent it, no spark/no ignition. During that brief moment that I thought all was good , I could see the aforementioned modified igniter glowing through the sight window. It appeared to right up against the burner then. I can only surmise that before bending the old and then trying the new one, that the tip was buried in the mesh. I think that as I’ve typed this out, I’m convincing myself that it is the burner and it must’ve also been corrupted and the 1 time it fired well for me was a fluke.
Anyway, anyone ever seen this? I’m going back tomorrow, hopefully, I want to be better prepared. Is there anything else I should be looking at?
did not test combustion,
Last service was June so 9 months. I think my company is eating this one.
Renter said they’ve been hitting reset for a couple months and each time “it seems to last not as long” I have no idea if the landlord was aware.
Guess I forgot to leave out the filler. Thanks for reading. I’ve been coming here from time to time for research. Appreciate this place
Comments
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Any chance you lost the orifice out of the gas valve doing all that work?
I did have this issue before but it was because the boiler was never converted to propane. Commercial property and none of the piping was labelled to indicate that the property was using propane. This was downtown and nobody ever thought of propane because why would you. Natural gas everywhere. It sounded like straight pipes on a Harley. it wasn't till i disconnected the gas that i smelled the propane. The boiler need a propane venturi.
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Can confirm it had been converted and the Orfice is in place.
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Measure the downstream vacuum on the gas valve. You should have a vacuum on the downstream side with combustion blower running and the gas valve closed. When the gas valve opens your vacuum should drop to almost nothing or just a have little vacuum. If your not in that neighborhood you'll have to adjust the gas valve. If the gas valve don't adjust its bad.
Did you change the gas valve?
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did not change the gas valve. Didn’t realize it’s a negative pressure valve at first, either. Kept looking for pressure after it’d open seeing none.
Am I gonna be able to try this vacuum idea at the combustion test port? I think I get what you’re suggesting…get the digital manometer ported in somehow…there is a flue sensor at the bottom of the HX but it’s kinda hard to access.
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i'm not familiar with IBC but most if not all have 2 test ports. Most are dungs or Honeywell.1 upstream on the gas valve and 1 downstream. Normally they are pretty much side by side on the top of the gas valve. Attach your gauge downstream. you might have to stretch your hose over the port. you need a thermostat screw driver to open the access port. sometimes they are real tight. i have an 8-way screw driver with a thermostat flat head that works great to open
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ahhh yes now I’m following. That goes back to the negative pressure valve I mentioned. There’s no measurable gas pressure on the outlet when it opens. But I didn’t try to see if there’s a vacuum. I was using my analog manomater so I don’t think that’d show a vacuum anyway?
If a new burner doesn’t solve things, this sounds like a good test, thanks! I did seem as though the explosiveness was an excess amount of gas
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You don't have 2 ports on your manometer?
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Not on the analog. I have a digital one that does
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Put it on the plus symbol. Then initiate a call for heat and watch
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good morning! Back on-site. pedmec, on the outlet side of this gas valve, during prepurge -1.3”wc and when the valve opens it drops to -.3”. Trial for ignition is like 4-5sec, if that. It cycles through an equally quick postpurge and the pressure jumps to -2.8”. The fan modulates up twice audibly then back down twice before the sequence starts again. I did this with the igniter disconnected and am about to attempt firing fo realz…
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seems the new burner was the final piece. Everything fired up and worked well, no more explosive starts! My anxiety was up, not gonna lie
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