Had a call where they said their dryer was sparking on hot water heater

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joshmurphy

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General Maintenance
I had a call the other night, and they told me that their stackable washer/dryer had sparked against their water heater.

I found that the breaker was also tripped. I discovered that the bonding strip was still in place on the back and it’s a 4 wire system. So I went ahead and removed that.

the washer/dryer and water heater were about a pinky width away from each other. Pretty much touching.

I know that the ground and neutral should not have been bonded, but I can’t see how it would spark against the water heater on a properly working system (no open neutral or open ground) and cause enough current to trip the breaker. Should I look further into this issue?

I should also note that I’m not an electrician, I’m currently in school to become one. I have a lot of experience from working in the maintenance field and that’s why I wanted to double check on this dryer issue. In case I need to call someone out. Thanks
 
Could be a lot of things. Best to call in a pro. Not just any old electrician though. A substantial percentage, maybe even a majority, won' t have a clue as to how to go about effectively troubleshooting this. Get an experienced service tech.
 
The neutral current of a residential washer dryer is probably the FLA of the motor, so perhaps 12 amps.
Since the neutral was bonded to the frame there was a parallel path for that neutral current, possibly 4 paths.
Since your in school learning ohms law take a second and diagram out this circuit.
You have a 120V load and 4 return paths;
The #10 white in the dryer circuit
The #10 Bare EGC in the dryer circuit

The #10 EGC in the water heater circuit, assuming its electric.
The metallic piping to the water heater if any.

Depending on the resistance of the water heater you could have had 1-4 amps trying to flow over it.
My electric water heater is next to the dryer, there is also a #4 bare bonded to the cold water pipe right at the water heater, as well as the #10 equipment grounding conductor with the 25A circuit.

Once you removed that strap there is no more parallel path.
If the sparking persists I would look into it further.
 
Most likely the water heater is not bonded, and either the water heater, or something connected to the waterlines (if metal) is faulted. Did you check for voltage between the water heater and the dryer? Turning the water heater off, voltage disappears? If no voltage, turn on the hot water until the water heater kicks on, then check again. Just a few of things to check.
 
Are we sure the appliance doesn't simple have a fault current energizing its frame therefore shorting out against a bonded water heater.
Try a tick tracer or widow maker what ever you guys call it there .. see if the chassis beeps or get your digital or induction tester find a good ground, not the water heater... and see if you get a reading off the appliance frame.

Unless the water system is energized and the appliance ground is the only properly grounded reference, very much unlikely.
 
It's more likely that the water heater is well bonded, and the dryer is 3-wire and the neutral is compromised.
 
hillbilly1 said:
Most water heaters nowadays are connected with non metallic plumbing, and if the dryer neutral is comprised, it would be acting up, or not run. OP did not mention that.
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and dryer wouldn't be moving to cause intermittent contact unless it were running either, so neutral must be good enough to allow motor to run at some level.
 
LarryFine said:
It's more likely that the water heater is well bonded, and the dryer is 3-wire and the neutral is compromised.
Click to expand...
The OP did say directly this is a 4-wire system. Trainee or not, I'm guessing he can count past 3.
 
If it's a stackable then it makes sense. I bet it only sparked when the washer was running. The dryer would use both phase conductors and the load will be balanced. But washers use line to neutral, so the load will send some of the current back on the neutral and the rest of the load back through the parallel path when it touches. Good call identifying the ground neutral connection at the equipment. I bet you would have gotten a heck of a shock if you were the bridge between the washer and water heater
 
Sea Nile said:
If it's a stackable then it makes sense. I bet it only sparked when the washer was running. The dryer would use both phase conductors and the load will be balanced. But washers use line to neutral, so the load will send some of the current back on the neutral and the rest of the load back through the parallel path when it touches. Good call identifying the ground neutral connection at the equipment. I bet you would have gotten a heck of a shock if you were the bridge between the washer and water heater
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Actually dryers are not a balanced load, the drum motor is 120 volts, so it can be used on a 208, or 240 volt service.
 
Does water heater have an EGC? Gas unit with natural convection for venting likely has no electrical connection at all other than possibly being bonded via metal water piping system. If you have one of those types of WH and there is no water pipe bonding (if you have metal piping system) in the premises the chance of voltage between piping and the electrical system grounded conductor certainly can be increased.
 
kwired said:
Does water heater have an EGC? Gas unit with natural convection for venting likely has no electrical connection at all other than possibly being bonded via metal water piping system. If you have one of those types of WH and there is no water pipe bonding (if you have metal piping system) in the premises the chance of voltage between piping and the electrical system grounded conductor certainly can be increased.
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True, the op did not mention wether it was electric or gas, we are just going on the assumption it was electric because the dryer is electric. We also don’t know if it’s a metallic or non-metallic water piping. Maybe the op will come back with more info.
 
hillbilly1 said:
Most likely the water heater is not bonded, and either the water heater, or something connected to the waterlines (if metal) is faulted. Did you check for voltage between the water heater and the dryer? Turning the water heater off, voltage disappears? If no voltage, turn on the hot water until the water heater kicks on, then check again. Just a few of things to check.
Click to expand...

I think this theory is best, given what we know, because you will not get a noticeable arc from breaking a parallel path if the first path has a properly low impedance to carry the full current. Not at 12A anyway. In this case, the dryer had not one but two paths back to the source (neutral and EGC), so the likelihood that both were compromised is reduced by half, one could argue.

Options to troubleshoot:
- turn off all breakers, fasten voltage probes to the two appliances, then turn on breakers one by one until you see voltage, then turn off and trace that circuit. There's no particular reason to believe the circuit in question will be for either appliance.
- Another option would be to test continuity between the MBJ and the water heater or the pipes attached to it. If no continuity, fix that with breakers off, then turn them on and see which one trips.
 
A non-contact tester will tell you which appliance is energized, as will a simple voltage test to a known ground.
 
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