Triangle Tube boiler is back firing
Thank you in advance to all who respond. My Prestige 175 which is a 2009 model, has never done this and all the sudden it is back firing. Literally shooting fire out the air intake tube that feeds the power blower. I service this unit myself, and have done so for years, and have never had this happen. I have read some threads of people who say this happens occasionally, but my unit never has until now. I'll done a lot of cleaning and checking, the last thing left for me to do is either replace the blower, or wait for my combustion analyzer to arrive on Tuesday and check the air/fuel mixture. But the unit will fire up no problem (I leave the cover off) and it begins to heat the water which is warming an indirect tank. I can see fire in the heat exchanger, and runs for 2 minutes, then a loud pop and blue flame comes out the air intake tube (turn down snorkel), and the flame in the combustion chamber is still on, but it keeps on back firing until I hit the off switch. So it seems to build up fuel in the blower and then starts to combust. Thank you in advance to anyone that has seen this before and can provide some insight.
Comments
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This might seem obvious but I'll say it anyway. This is a dangerous condition. Shut it off.
A combustion analyzer and a manometer are needed to tune it properly. An experienced tech is best. Delayed ignition pops and harmonic fog horn stuff happen with theses units when the tune is wrong. What you are describing is not that. Guessing about what's causing combustion on the intake side isn't smart. I would want to take this unit apart and inspect everything carefully proving all parts are undamaged before I attempted to tune it. If there is an existing part flaw, tuning it to compensate for it is a bad idea. Look closely at the venturi but also the blower, burner, gas valve ,heat exchanger and complete flue. Static and dynamic gas pressures checks are a must. Throttle and bias adjustment next if needed. Triangle tubes tuning instructions are good. Carefuly check your studs that hold down the top of the combustion chamber. I've found many sheared off. Loosen the nut only. Don't tighten them more to check them.
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Propane or natural gas?
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
propane
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as I said on H-Talk.
this unit has NOT been serviced Properly. No combustion analysis performed.Shut it down.
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When was the last time the heat exchanger tubes were cleaned? Propane and 2009, they could be well clogged up. Is this happening on low fire? Meaning, the boiler fires up then modulates down and then it starts to back fire? The logic of the gas valve to the blowers air movement is to always maintain a negative pressure and fix ratio. If the HX is clogged and restricts the blowers low speed air flow and the gas valve is tuned very rich or leaks, I can see this happening. Don't tinker with propane. Paying for competence, if you can find it, is well worth the cost.
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I would think a few different safety’s would shut that down long before that can happen!
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Is that picture from a Space-X launch?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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only they don’t use PVC as the firing cone!
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