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Old 01-14-2012, 10:58 PM   #31
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Burner flame sputters


Sorry for the delay, things have been a little busy. And sorry, no pics.

Anyways, looks like replacing the heat exchanger worked. The burner no longer sputters. However, the tech thinks the exchanger may have been plugged and not leaking.

When he was removing the exhaust pipe between the furnace and chimney liner, he found some debris that he said was due to corrision in the liner. He said the liner may be too large of a diameter for the size of furnace and rise of my house. A 6" liner was installed but it should have been a 4" liner. 66000btu + approx 40 ft rise.

Where the exhaust is located on the furnace, any debris from the pipe would fall into the left most exhanger chamber 1st. Comments?

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Old 01-14-2012, 11:02 PM   #32
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Burner flame sputters


for the size of furnace a six inch liner is over kill.. even at a height of forty feet.

With out looking at the chart I would say a four inch liner for sure with insulation sleeve around exterior of line or a five inch.
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Old 01-14-2012, 11:04 PM   #33
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Burner flame sputters


Glad you got it fixed...and get a CO detector.
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Old 01-15-2012, 07:46 AM   #34
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Burner flame sputters


It was definitely leaking. Bad weld/crimp joint or whatever they use which opened up from heating and expansion. It was DIRECTLY related to the fan coming on and air pressure so a blockage would not cause a problem as it would do it when the fan was off. There is a pressure switch to stop the burner if the chimney is blocked or from blockages so that was not the problem. Having seen that type of flame many times from cracked heat exchangers I could tell. Blockages give you a slow buildup of gases and slow flame rollout out the front of the burners. Your flame problem happened quickly and at the exact time the fan started. Debris cannot get into the heat ex as it gets stuck in the exhaust fan first.
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Old 01-15-2012, 10:30 AM   #35
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o
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Originally Posted by yuri View Post
It was definitely leaking. Bad weld/crimp joint or whatever they use which opened up from heating and expansion. It was DIRECTLY related to the fan coming on and air pressure so a blockage would not cause a problem as it would do it when the fan was off. There is a pressure switch to stop the burner if the chimney is blocked or from blockages so that was not the problem. Having seen that type of flame many times from cracked heat exchangers I could tell. Blockages give you a slow buildup of gases and slow flame rollout out the front of the burners. Your flame problem happened quickly and at the exact time the fan started. Debris cannot get into the heat ex as it gets stuck in the exhaust fan first.
that's good to know. The exchanger is crimped at the edge and riveted in the center. There were some dark Grey discolored areas in several different spots on all 3s
exchangers. The rest of it was a normal stainless color.

Do you think the corrosion and oversized liner is something I should deal with or leave alone?
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Old 01-15-2012, 12:03 PM   #36
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Burner flame sputters


If the chimney goes thru the middle of the house and stays warm it should be OK. If it goes thru an exterior wall and can get cold then that is a huge problem as condensation can occur. Then it should be downsized and replaced with a B vent ( pipe within a pipe ) type liner/vent to meet the code.
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Old 01-16-2012, 05:45 PM   #37
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Burner flame sputters


Thanks Yuri. Yes the Chimney is in the center of the house. The last 5 feet of the liner is exposed but is encased in a steel liner covered with vent cap.

About 6 years ago, after the furnace and liner install, we had some chimney work done. The exterior of the brick was re-pointed and a cenement cap was placed over the chimney for asthetic purposes. Unknown to us at the time, the mansonary guys cut the liner vent cap and squashed it down to fit the cement cap on. There were still exhaust openings but the cap basically lost 50% of its venting area. Could this have caused excessive condensation in the liner? The brick chimney was removed approx 5 years ago when our roof was done. I'll try and dig up some old pictures.

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Old 01-16-2012, 05:50 PM   #38
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yep. it could have.
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Old 01-16-2012, 06:30 PM   #39
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Burner flame sputters


If it worked OK for 6 yrs then it should not have caused your heat exchanger problems or any condensation. However it should not have 50% of its area reduced and that does not meet the code and can cause pressure switch tripping problems or tripping of the spill switch etc. Sounds to me like you should get a proper 4" B vent installed for the safety of your family and to meet the code irregardless of the aesthetics. Make sure they size it properly taking into account the horz run from furnace to chimney and look it up in the code book. Should also have B vent from the furnace to the chimney.

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