Just never know when you need a breaker to trip.

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david

Senior Member
Location
Pennsylvania
Woke up this morning the house was cold the basement lighting circuit had tripped. Gas furnace wired to the same circuit fused blown at furnace.

No matter what our background we just never know when we will need the fail safes built into a mechanical system and a electrical system to work
 

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qcroanoke

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
david said:
Woke up this morning the house was cold the basement lighting circuit had tripped. Gas furnace wired to the same circuit fused blown at furnace.

No matter what our background we just never know when we will need the fail safes built into a mechanical system and a electrical system to work
Click to expand...

Wow! Glad you and family are ok!
Did you have a smoke detector in the area?
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
david said:
Woke up this morning the house was cold the basement lighting circuit had tripped. Gas furnace wired to the same circuit fused blown at furnace.

No matter what our background we just never know when we will need the fail safes built into a mechanical system and a electrical system to work
Click to expand...
That looks extreme indeed.
Not enough information in the photo for full forensic analysis, but I would sure suspect the temp sensor or relay in the box near the top left.
Also possible would be a blow-back on ignition of the burner for some reason, with the heat damage affecting only the wiring and depositing the smudge from the insulation near the top.

Let us know what the HVAC dude has to say.

PS: I hope that bushing hanging on the thermocouple lead is part of a universal assembly and is simply not used with your mounting configuration.
 
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david

Senior Member
Location
Pennsylvania
I will speculate,

the fuse blew at the furnace and shut off the gas allowing the fire source in the control area to lose fuel. (gas). The compartment had been exposed to the gas fire long enough to ignite the insulation on the wiring in the control compartment causing a short circuit to the branch circuit feeding the appliance and tripping the branch circuit breaker. After burning most of the insulation in the control compartment the secondary fire ran out of fuel and went out.
 
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GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
david said:
I will speculate,

the fuse blew at the furnace and shut off the gas allowing the fire source in the control area to lose fuel. (gas). The compartment had been exposed to the gas fire long enough to ignite the insulation on the wiring in the control compartment causing a short circuit to the branch circuit feeding the appliance and tripping the branch circuit breaker. After burning most of the insulation in the control compartment the secondary fire ran out of fuel and went out.
Click to expand...
That sort of thing is one reason that modern furnaces tend to be built with sealed combustion chambers and forced combustion air fans (with flow switches.)

Possibly there was a wind eddy problem where the flue pipe from the furnace ends. Or maybe a suction source like a clothes dryer running in the same too-tightly-sealed basement.
 
T

templdl

Senior Member
Location
Wisconsin
david said:
I will speculate,

the fuse blew at the furnace and shut off the gas allowing the fire source in the control area to lose fuel. (gas). The compartment had been exposed to the gas fire long enough to ignite the insulation on the wiring in the control compartment causing a short circuit to the branch circuit feeding the appliance and tripping the branch circuit breaker. After burning most of the insulation in the control compartment the secondary fire ran out of fuel and went out.
Click to expand...

I'm thinking along the same lines as you are. It certainly wasn't electrical. Either there was a backflash out of the combustion chamber or the burners weren't lit immediately and there was a gas built up enough that it entered the area pictured the burners finally ignited extending the flam to the area as pictured and the electrical control circuit which by pure luck tripped the branch circuit breaker shuting off the valve shutting off the gas.
The lord had to be looking out for you on this one.
 
D

david

Senior Member
Location
Pennsylvania
Please note i am taking an educated guess as to what caused this fire.

We closed on this house last summer. After closing we became aware that the air conditioning pump out side had stopped working.

The house has a one year home warranty that was to cover most of that repair. The outside unit needed replaced. The inside coils for the new unit did not match in size the existing coils. I had to pay extra for the hvac guys to reconfigure the duct work for the new inside coils. The new air system worked great all summer.

I remember when the HVAC guys where getting ready to leave the one tech. ask me if I had a lighter. He said he needed to relight the pilot for the furnace. The hot water tank and furnace are in the same utility area.

I told him I keep a box of matches above the utility door. I said I keep them there to be out of reach from the six year old. He said thanks. I went about my business they finished the job and left.

When I pulled the furnace cover this morning I noticed the small stick of left over match laying between the middle and left flow tube that directs the gas into the fire box. The match stem caught my eye only because I always roll up a wick from a piece of paper when I am lighting a gas appliance.

I then notice and you can see in the picture that the left tube was out of place knocked slightly off the gas nozzle feeding the tube.
I speculate that the HVAC tech last summer when he lit the pilot reached in with a wooden match between the middle and left feed tube to light the pilot accidently pushed against the left tube and did not notice it out of place. The vibration from the blower motor further displaced the tube or just the right amount of gas entered the control chamber from the dislodged feed tube and ignited last night causing a fire in the compartment
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
david said:
I then notice and you can see in the picture that the left tube was out of place knocked slightly off the gas nozzle feeding the tube.
I speculate that the HVAC tech last summer when he lit the pilot reached in with a wooden match between the middle and left feed tube to light the pilot accidently pushed against the left tube and did not notice it out of place. The vibration from the blower motor further displaced the tube or just the right amount of gas entered the control chamber from the dislodged feed tube and ignited last night causing a fire in the compartment
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I would not call that "slightly out of place"! :) If there is no overlap at all, they are disconnected pure and simple.
If the unit was that way before the fire, it certainly would explain it.
Does the first repair guy have malpractice insurance?
If it was that way after he lit the pilot, he must not have tested energizing the burner with the pilot lit. A really bad practice IMHO, even it if was the middle of summer.
 
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david

Senior Member
Location
Pennsylvania
To keep the house off the market I had to rent the house prior to the bank closing the loan.

We lived there last winter and the furnace worked fine all winter.

I had to replace the hot water tank but I replaced that myself. I had no problem with the furnace last winter.

The tube was displaced before the fire and the only ones in there where the HVAC guys last summer.

There will be no legal action, thankfully no one got hurt. There is a lot of burnt smell that will take some time to get rid of.

The HVAC contractor is a real decent guy, the technician he sent out made a mistake,
I did make them aware of the fire and the owner came out and looked at the furnace. He did put the tube back in place and he came up with an estimation of around $750.00 to rewire and replace components in the furnace.
 
readydave8

readydave8

re member
Location
Clarkesville, Georgia
Occupation
electrician
david said:
To keep the house off the market I had to rent the house prior to the bank closing the loan.

We lived there last winter and the furnace worked fine all winter.

I had to replace the hot water tank but I replaced that myself. I had no problem with the furnace last winter.

The tube was displaced before the fire and the only ones in there where the HVAC guys last summer.

There will be no legal action, thankfully no one got hurt. There is a lot of burnt smell that will take some time to get rid of.

The HVAC contractor is a real decent guy, the technician he sent out made a mistake,
I did make them aware of the fire and the owner came out and looked at the furnace. He did put the tube back in place and he came up with an estimation of around $750.00 to rewire and replace components in the furnace.
Click to expand...
He wants $750 to fix something he broke?
 
kwired

kwired

Electron manager
Location
NE Nebraska
GoldDigger said:
That sort of thing is one reason that modern furnaces tend to be built with sealed combustion chambers and forced combustion air fans (with flow switches.) I think that may be more of a side effect, and the real reason they have changed designs has more to do with efficiency.

Possibly there was a wind eddy problem where the flue pipe from the furnace ends. Or maybe a suction source like a clothes dryer running in the same too-tightly-sealed basement.
Click to expand...

Some units had a "flame roll out" sensor that may have stopped this from proceeding to the damage level that happened here.
 
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