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Exploding furnace continued

6420 Views 45 Replies 14 Participants Last post by  BayouRunner
In frigid Feb I posted this thread regarding loud explosions. Since that time I've cleaned the thing ad infinitum and still the house-shaking booms. So I no longer think it's a dirty furnace. Check out the attached image.



Sounds I hear:
00:00 I hear an actuator whirring. It's about the happen!
01:07 I hear a soothing series of clicks accompanied by the high pitched creaking of a rusty duct opening from the flue area.
01:15 Clicks and rusty sound stop.
01:18 Loud click (gas valve opening?) followed by gas flow sound.
01:22 BOOM!

Observation:
4 seconds between gas flow and detonation. Blue flame rollout from the top. Smell of gas and soot. Bigger the boom, the more distinct the gas and soot smell.

Hmm.....
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Looks like its time for a new furnace. Just saw your other post. Too late now but I usually pull the whole burner assembly out and clean it. They get debris inside and out as well. I wouldn't even think about trying it again but if you are get a good tech to look at it. Turn off the gas in the meantime and remove the power
thats one way to clean the cobwebs out of it...................
4
Thank you for your concerns for my safety but I have been surviving under these conditions all winter. I am a single middle-aged man with no kids. If I were married I am pretty sure my wife would have had me fix/replace the fiery beast two years ago.

1. Initial ignition centered around pilot. You can make out the blue flames over the two center ribbons.


2. Boom! Blue flames coming out from bottom and top. How did the flame get all the way up there?


3. Worst is over. Orange coming in on bottom.


4. All orange at the bottom. Stable and humming.


The video shows 4 seconds of gas flow before ignition.
How could just a few seconds of gas flow cause such a massive explosion?

Key point: this never happens on the initial boiling cycle. It happens when I'm frequently cycling to get from say 55 degrees to 65 degrees.
Perhaps gas is getting trapped in the system between cycles. Anyone ever hear of such a thing?
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There is something wrong with your burners. I suspect that there is some blockage causing the gas to come back out of the burners. This is really dangerous and I would not run this furnace at all. I've been doing this work for over 40 years. I urge you not to use the furnace, I don't feel any internet diagnose would be the way to go with this one. I enjoy helping people out and to help them save a buck. But I really feel you need to get some professional help on this one.
BayouRunner,

Thank you for your concern. I don't believe there's blockage though. While I could not pull out the entire assembly, I did ramrod the ribbons with a venturi
brush as suggested from the earlier thread as well as rebrush the tops vigorously and leaf blow.

I felt the openings leading from the gas manifold to the ribbons, and wow, they are truly pinholes -- literally anything wider than a pin can't be thrust into the manifold. So the amount of gas that could conceivably accumulate in 4 seconds seems not enough to cause the explosion. It's just bewildering.
Thanks again.
Unless you have some advanced tools needed for proper diagnosis, I'd urge you to shut the furnace down and have it looked at. I know this is a DIY site but that furnace is an outright hazard to you and your home, and likely requires more then an Internet DIY site can provide. I've personally witnessed such equipment burn down buildings and severely injure service personnel.
Allowing that to continue, can and will cause severe irreversible damage to the equipment.
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I have a feeling there is gas leaking into an area other than where it is designed to be entering. When the LEL ( lower explosive limit ) is reached ( air to gas ratio ) the BOOM happens.

If it happened once in my furnace it would be history.
Not an expert but can read manuals.
http://www.utcccs-cdn.com/hvac/docs/1009/Public/0A/OG-BS1A-03.pdf

Pg. 8 of 12
COMBUSTION AREA AND VENT SYSTEM
. . . Accumulations on the main burners can result in the burners firing out of normal sequence. This delayed ignition will create an alarmingly loud sound.
CAUTION: If your boiler makes an especially loud noise when the main burners light, shut down your boiler and call your dealer.
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Looks like someone bypassed the roll out switches on it.
In frigid Feb I posted this thread regarding loud explosions. Since that time I've cleaned the thing ad infinitum and still the house-shaking booms. So I no longer think it's a dirty furnace. Check out the attached image.



Sounds I hear:
00:00 I hear an actuator whirring. It's about the happen!
01:07 I hear a soothing series of clicks accompanied by the high pitched creaking of a rusty duct opening from the flue area.
01:15 Clicks and rusty sound stop.
01:18 Loud click (gas valve opening?) followed by gas flow sound.
01:22 BOOM!

Observation:
4 seconds between gas flow and detonation. Blue flame rollout from the top. Smell of gas and soot. Bigger the boom, the more distinct the gas and soot smell.

Hmm.....
just build a mantle around it and call it a fireplace..........
beenthere said:
Looks like someone bypassed the roll out switches on it.
I was wondering why they hadn't tripped
I hope the OP gets some pro help before he turns into a statistic.

Google "exploding house from faulty furnace".


https://www.google.com/search?q=exp...vT7uDLAhUHNSYKHUchDaUQsAQIHA&biw=1307&bih=606
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I hope the OP gets some pro help before he turns into a statistic.

Google "exploding house from faulty furnace".


https://www.google.com/search?q=exp...vT7uDLAhUHNSYKHUchDaUQsAQIHA&biw=1307&bih=606
I spent 3 weeks in a burn unit, and several months in physical therapy, due to an "exploding furnace". I still suffer from the effects, and wear the scars, 5 years later.
If this, or loosing your home to fire, is worth it for a DIY project, then carry on. But not being able to shower, and having to wake up in the middle of the night to take more pain medication and slather on more burn cream, sure can get a little annoying.
You have a time bomb ticking away in your home there.
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If the burners are dirty and it has not be burning cleanly then the flue passages where the smoke go thru have soot on them or are partly plugged and you are not getting enough draft thru the boiler. You are getting a incorrect draft>fuel to air mixture and that is part of the problem. Your gas valve may also be sticking and not opening fast enoough.

You really need a Pro to check for all these problems. Good chance it is also producing and leaking CO carbon monoxide out the front from improper draft.

On startup when cold it will have a different amount of draft up the chimney/thru it than when warm from running. That is not the real problem though.
Looks like someone bypassed the roll out switches on it.
Yes, I'm embarrassed to say I disabled the spillout some years ago to keep the furnace going.

The responses to invoke professional help are well received. Fortunately, I've made it through another winter unscathed, and it's warm enough outside to stop having to roll the dice. I will spend the big bucks.
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Yes, I'm embarrassed to say I disabled the spillout some years ago to keep the furnace going.

The responses to invoke professional help are well received. Fortunately, I've made it through another winter unscathed, and it's warm enough outside to stop having to roll the dice. I will spend the big bucks.
It's highly dangerous to disable any safety device. I'm not trying to start a disagreement but if this is your idea of a "fix" then you don't have the ability, skill or knowledge to be working on the equipment. It's stupid ideas such as these that lead to people dying.
Turn that thing off immediately.
You didn't "fix" anything by bypassing the switch. You created a very dangerous situation.
Not trying to be dramatic or mean but it can build up enough gas and pressure when it explodes so that the vent pipe may blow off the boiler leading to the chimney. They are not meant for high pressure or explosions and if it is thin or old and corroded may get a hole blown in it. You may die from CO.

I have heard stories of the front door of furnaces being blown off from delayed ignitions.

I have had a dozen or more bad delayed ignitions but lucky I learned to stand to the side of the furnace. Worst incident was a furnace flooded with oil that caught fire and would not stop. Had to call the fire dept to babysit it until it burnt out.
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