How did this clothes dryer circuit start a fire?

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TAH said:
The ground was not intact back to the panel. At the dryer, he put the green wire where the red wire was supposed to go.
I took that green wire off the red terminal, and the motor won’t spin at all.
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I think he was just trying stuff until he got the motor to spin and the breaker to not trip. Then he figured he had it correct
 
TAH said:
The ground was not intact back to the panel. At the dryer, he put the green wire where the red wire was supposed to go.
I took that green wire off the red terminal, and the motor won’t spin at all.
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Oh, I missed that. Just went back and saw where you had said that.

So basically one hot and the bare neutral got swapped in the dryer makeup compartment.

What happened in the receptacle is irrelevant to the circuit because it was connected color-to-color
 
hbiss said:
You wouldn't happen to have the make and model of this dryer so we could look up the schematic, would you??

-Hal
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I’ve asked the fire marshal for that at least 10 times and he has failed to get it to me. I will post it when or if he does
 
hbiss said:
The 120V motor circuit had 240 on it only when the dryer was turned on. How often was it used during those 3-4 days?


The white was landed on the breaker along with the black. So it's 240V between one phase and neutral on the dryer terminal block.



There would have been a BIG arc when someone plugged in the dryer plug- unless the breaker was off.



It was. With 240V on it.


-Hal
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Yep, I’m not disputing that. Basically what I stated.
 
TAH said:
The ground was not intact back to the panel. At the dryer, he put the green wire where the red wire was supposed to go.
I took that green wire off the red terminal, and the motor won’t spin at all.
Click to expand...

Ahh, I missed that too.

TAH said:
At the dryer terminals the 3 wire with ground dryer cord was wired black to black, white to white, green to the terminal that normally receives the red conductor, and red to nothing. The bonding jumper from the white terminal to the dryer casing was left in place.
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James L said:
So basically one hot and the bare neutral got swapped in the dryer makeup compartment.
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Ok. You still had 240 between white and black which puts 240 between L1 phase and the Neutral on the dryer terminal block as well as 120V on the dryer frame through the bonding jumper.

The bare or ground was connected to the ground bar at the panel. At the dryer it connects to the L2 phase.

So at the dryer terminal block you had:

L1 to L2=120V
L1 to N= 240V
L2 to N= 120V

Apparently the dryer motor and controls were wired L2 to N which is why it worked and stopped when you disconnected the ground from the L2 terminal.

So the question is how is that dryer wired internally and what would happen if there were 240V between L1 and N.

I just might be that this fire started because of the dryer frame having 120V to ground on it and it arcing to something in the presence of something combustible like lint.


-Hal
 
I agree with Augie and Hal that having the dryer frame connected to one of the phases leaves a lot of vulnerabilities in the vent system. The vent system would have no intentional isolation from other metallic objects which might provide a ground return path, possibly at some distance from the dryer. Poor connections at such points of contact could cause arcing and/or heating and possibly start a fire. Lint inside the duct would be easily ignited. Also portions of the vent system might be hidden so that a smoldering fire might not be noticed.

I'm very sorry for your tragic loss.
 
synchro said:
I agree with Augie and Hal that having the dryer frame connected to one of the phases leaves a lot of vulnerabilities in the vent system. The vent system would have no intentional isolation from other metallic objects which might provide a ground return path, possibly at some distance from the dryer. Poor connections at such points of contact could cause arcing and/or heating and possibly start a fire. Lint inside the duct would be easily ignited. Also portions of the vent system might be hidden so that a smoldering fire might not be noticed.

I'm very sorry for your tragic loss.
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I agree. Looks like the venting system may be the culprit here.
 
Another thought is that foil backed insulation could provide a conductive path from the vent duct over to something that's grounded and which might be some distance away. And so arcing and/or heating from a poor connection might occur at that distant point and cause a fire.
 
hbiss said:
You wouldn't happen to have the make and model of this dryer so we could look up the schematic, would you??

-Hal
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Appliance Tech here. Unless this is a weird off brand we can assume a lot of things as most dryers are very similar in their circuits. There is no way this machine ran and heated with the way described above, unless the heater also failed to ground. Electric dryers need 240 for the heater which is Black L1 and Red L2. 120 for the motor. L1 Black and N white.

Heat circuit:
From the dryer t-block L2(red) goes directly to the motor centrifugal switch. (This is not in the motor windings circuit just a switch that closes when the motor is running). From the motor to the heater through a HighLimit T-stat and High limit fuse (back up for T-stat failure both are on the heater can). From there goes to the cycling control (either a mechanical t-stat on blower then a timer or a computer board which takes the thermistor reading from the blower). From the control L1 comes from the t-block black.

Motor:

Black Line1 terminal blcok to timer through to the motor thermal fuse, then a start switch, belt switch, door switch and now the motor. From motor wire goes to Neutral terminal block. (some models the door switch is on the neutral side of the motor.
Here's a old video I did a while ago chatting about a mechanical Whirlpool built model.

 
TAH said:
This fire killed my 14-year-old son. And I am devastated. I can’t believe my son died in an electrical fire. All of your help, thoughts, and input are greatly appreciated
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:eek:
Condolences , i am both an electrician, and a former FF
Other than sorry for your loss, there are no words.....

~RJ~
 
If the vent had current though it and lent in the vent itself, I would say it’s a high possibility that’s how this fire started.

I too am sorry for your lost, I pray that the God of peace will comfort you and your family at this time.


“ shoot low boys their riding shetland ponies”
 
Thank you to all of you. Your input is greatly appreciated. This is a nightmare for me.
I know this dryer wiring started the fire, probably because of the voltage to the duct, but really trying to figure it out has become extremely important to me. I just have to know.
I have an old dryer set up in my yard and I have been testing it. If you read my original post there’s lots of details in there. If anyone can think of other diagnostics I can do, I’d be happy to do them and post them.
I can’t reconcile why this took 3 to 4 days for the fire to start and why it appears the fire may have started at or near the circuit breaker panel.
 

This is great.
I think the heater was only working at some fraction of normal.
The incomplete circuit to the motor is a factor to consider.
I think the vent was flexible foil. Terrible stuff.
 
First and foremost, very sorry for your great loss.
I don't have much to offer as to the cause beyond what already stated by others. But I have seen an overload that the breaker didn't clear, very old panel and breakers, and after several overloading events over a period of time (days to maybe week and a half, the time period a contractor was using a bad saw) had weakened the connections through heating and cooling enough that one final event set the panel burning, just happened to be working nearby to witness the beginning of ignition and able to get to the main disconnect and shut power off before it actually burst into flame. Got hot enough to actually welded the breaker onto the bus, and melt the feeder. Found the causing event because after panel was replaced the same contractor came back and used the same saw and tripped the breaker, tested and found the saw was indeed faulty.
 
It seems to me that he brought 240 volts to the dryer receptacle but wired that 240 Volts line to neutral in the receptacle where it should have been 120 V.

I don't know how the thing ever actually worked at all
 
petersonra said:
It seems to me that he brought 240 volts to the dryer receptacle but wired that 240 Volts line to neutral in the receptacle where it should have been 120 V.

I don't know how the thing ever actually worked at all
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It only works when you wire the ground to L1. As far as I can tell, the circuit seems to be working in the opposite direction of the way it was intended. Like a 120VAC motor that runs on a reverse polarity receptacle. The dryer vent seems to be searching for the completion of the circuit.
I have this all set up in my yard so I can test different scenarios
 
Fred B said:
First and foremost, very sorry for your great loss.
I don't have much to offer as to the cause beyond what already stated by others. But I have seen an overload that the breaker didn't clear, very old panel and breakers, and after several overloading events over a period of time (days to maybe week and a half, the time period a contractor was using a bad saw) had weakened the connections through heating and cooling enough that one final event set the panel burning, just happened to be working nearby to witness the beginning of ignition and able to get to the main disconnect and shut power off before it actually burst into flame. Got hot enough to actually welded the breaker onto the bus, and melt the feeder. Found the causing event because after panel was replaced the same contractor came back and used the same saw and tripped the breaker, tested and found the saw was indeed faulty.
Click to expand...
This is possible. It was a 2-30 square D QO breaker, which I have a lot of faith in, but I will run the mocked-up dryer many times to see if it damages the circuit breaker in any way.
 
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