What could happen if stove bond iffy on 3 wire?
- Thread starter Cletis
- Start date
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JFletcher
Senior Member
- Location
- Williamsburg, VA
Well...
The worst that could happen is that poorly installed bond comes loose, leaving the frame of the dryer isolated from a fault path.
A fault from one of the grounded conductors or the motor happens to occur while somebody is drying a huge pile of oily shop rags in a large petrochemical processing plant, inconveniently situated next to a nuclear power plant, and biological weapons manufacturing facility....
(There are no zoning ordinances in SimCity)
I'll spare you the lurid details and intermediate storyline, but sufficed to say that the improperly installed bond was butterfly zero that ultimately resulted in the entire destruction of the known Universe.
That's the worst that could happen...
Back to real life now, if the dryer frame is not bonded to the neutral conductor, and a fault occurs in the dryer, is going to sit at 120 volts and probably zap somebody when they're pulling wet clothes out of the washer and putting them into the dryer.
Eta: ditto with a stove, which is what you asked about, just substitute a cooking misadventure into the above storyline.The stove frame would be energized, and potentially zap somebody who is touching a bonded object.
The worst that could happen is that poorly installed bond comes loose, leaving the frame of the dryer isolated from a fault path.
A fault from one of the grounded conductors or the motor happens to occur while somebody is drying a huge pile of oily shop rags in a large petrochemical processing plant, inconveniently situated next to a nuclear power plant, and biological weapons manufacturing facility....
(There are no zoning ordinances in SimCity)
I'll spare you the lurid details and intermediate storyline, but sufficed to say that the improperly installed bond was butterfly zero that ultimately resulted in the entire destruction of the known Universe.
That's the worst that could happen...
Back to real life now, if the dryer frame is not bonded to the neutral conductor, and a fault occurs in the dryer, is going to sit at 120 volts and probably zap somebody when they're pulling wet clothes out of the washer and putting them into the dryer.
Eta: ditto with a stove, which is what you asked about, just substitute a cooking misadventure into the above storyline.The stove frame would be energized, and potentially zap somebody who is touching a bonded object.
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
First, the bond is the appliance cabinet to the neutral, allowing the neutral to provide grounding, not the other way around, so the neutral must be a wire installed to neutral requirements.
Second, the neutral conductor must remain on the neutral terminal, and either the wire grounding conductor, or a metal strap, must connect the appliance cabinet to the neutral terminal.
Added: A few years ago, we investigated a severe shock to a child caught between the range and the sink. Someone had relocated the range, feeding the power cord up from the crawl.
The real kicker: at the other end of the cord, someone ran a single strand of each conductor of the original range conductors through the hole in the blade of the plug, and taped them.
Over time, the tension pulled the cord's neutral conductor out of the crimped-on spade or ring terminal, which energized the cabinet. They mentioned the clock and lights recently quit.
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Results
Results
I'm going to ruin the anticipation here. Here is what happened. I got a call for a new stove that "blew up with flames coming out back and large booms"! So off I went. Here is what I discovered.
Burn marks all over blower motor under stove
Melted 3 prong stove cord (just 12"-24" section) this was part under the stove on top of motor housing
Melted motherboard and capacitor on stove
Bonding strap was attempted to be put on green screw but someone skinned it and tried wrapping but barely even touching green screw with most threads melted but on a couple left with burn marks around green screw
Totally melted stove cord right in middle with conductor exposed
On 40 amp 2 pole federal pacific 40 amp breaker that eventually tripped
Stove worked for about 2 months then the above happened
Pics coming...
Ran new 6/3 and 4 prong 50 amp outlet
Results
I'm going to ruin the anticipation here. Here is what happened. I got a call for a new stove that "blew up with flames coming out back and large booms"! So off I went. Here is what I discovered.
Burn marks all over blower motor under stove
Melted 3 prong stove cord (just 12"-24" section) this was part under the stove on top of motor housing
Melted motherboard and capacitor on stove
Bonding strap was attempted to be put on green screw but someone skinned it and tried wrapping but barely even touching green screw with most threads melted but on a couple left with burn marks around green screw
Totally melted stove cord right in middle with conductor exposed
On 40 amp 2 pole federal pacific 40 amp breaker that eventually tripped
Stove worked for about 2 months then the above happened
Pics coming...
Ran new 6/3 and 4 prong 50 amp outlet
JFletcher
Senior Member
- Location
- Williamsburg, VA
Heh, I wasn't *too" far off...
You probably want to have a look at that two pole 40 amp FPE as well. Can't wait to see the pics.
You probably want to have a look at that two pole 40 amp FPE as well. Can't wait to see the pics.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
The loose bonding screw/strap was not the cause of all this, the result maybe, but not the cause. That's if the grounded conductor was landed in the neutral terminal on the stove. There had to be a fault to the frame and the loose bonding connection caused a high resistance resulting in the heated/burnt items in the path. Also why the breaker didn't trip when the fault occurred.
Ok. I agree with you. Here is what is puzzling so far. It didn't overheat (or enough to melt) at connections (which were solid) it overheated and melted where cord was pinched between stove exhaust housing and under stove where slid in?? So it sounds like there was a fault that would not clear and stove metal got hot somehow?
kwired
Electron manager
- Location
- NE Nebraska
Was power supply cord neutral conductor landed on "neutral" or "appliance frame" side of the bonding jumper? Was "neutral" end of bonding jumper connection tight?
Presuming the supply cord conductor(s) was anything between 10 AWG and 6 AWG, I don't see enough current flowing, especially as a result of open neutral issues, to get it hot enough to melt the cord, unless there was short circuit or ground fault current flowing and OCPD failed to open in timely manner. You did mention it was a FPE breaker.
info
info
Yes, the grounded conductor landed on neutral bolt very solid BUT the #10 stranded white bonding jumper was skinned (and maybe for cut off??) and the installer attempted to wrap around green screw but wasn't even behind it just barely touching metal frame.
info
Yes, the grounded conductor landed on neutral bolt very solid BUT the #10 stranded white bonding jumper was skinned (and maybe for cut off??) and the installer attempted to wrap around green screw but wasn't even behind it just barely touching metal frame.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Obviously, the damaged cord energized the cabinet.
Yes, but what would make a cord fail 12-24" from the connection?? very odd phenomena. I'm sure it happens. Maybe when they jammed stove back in it got pinched/nicked ? but that some really thick stove cord insulation though
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
And possibly put 240V across a 120V control board (compromised neutral).
Also, the stove ran fine for about 3 months after the install. It seems if they nicked it right away it would have went bad right away or way quicker ?? I could barely put a brand new razor blade through that stuff that's why it's hard to believe that happened but I'm sure its possible
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
It is barely theoretically possible that some pinching configurations could result in local inductive heating which might end up eventually causing insulation failure.
Also, it is possible that the wire used to make the connection was not properly rated for the temperature conditions at that location within the stove.
Just blue sky thinking, not likely explanations.
Also some plastics which are hard to cut can still cold flow over time under sufficient pressure.
Also, it is possible that the wire used to make the connection was not properly rated for the temperature conditions at that location within the stove.
Just blue sky thinking, not likely explanations.
Also some plastics which are hard to cut can still cold flow over time under sufficient pressure.
JFletcher
Senior Member
- Location
- Williamsburg, VA
No $0.10 pop-in connector or NM clamp on the cord where it goes through the metal, no wonder the original installer got the cord pinched between the frame and motor or wherever.
The devil is always in the details...
I don't think we need Quantico to figure out that extremely poor installation is what caused this failure.
Eta: was trying to quote the picture in post number 13
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