For those of you who like receptacle stabs

[goldstar]

I went on a service call yesterday after a HO called said that on Xmas day they heard a pop in the kitchen and then started to smell things burning in several rooms. They began unplugging everything they could. Unfortunately.....they were too late. Some 15 or 20 years ago the rocket scientist who wired their kitchen decided to run a 12/3 RX to a kitchen counter JB and back-stab the feed neutral into the receptacle (BTW, there were no GFI's in the kitchen). Wrapped around the screws were the neutrals feeding each of the two MWBC's. Aside from the receptacle and wires burnt at that location the following appliances were among the victims : refrigerator, microwave, range-oven, computer, monitor, modem, (CATV box, television, stereo, VCR in the next room). He mentioned that his insurance was $5K deductible. I think he's exceeded that. In addition to those problems I checked the breaker panel. Each neutral was landed on the ground bar along with its respective EGC under the same screw. Several (including the MWBC in question) were loose. I'm surprised this house didn't burn down.

 

[hurk27]

I went on a service call yesterday after a HO called said that on Xmas day they heard a pop in the kitchen and then started to smell things burning in several rooms. They began unplugging everything they could. Unfortunately.....they were too late. Some 15 or 20 years ago the rocket scientist who wired their kitchen decided to run a 12/3 RX to a kitchen counter JB and back-stab the feed neutral into the receptacle (BTW, there were no GFI's in the kitchen). Wrapped around the screws were the neutrals feeding each of the two MWBC's. Aside from the receptacle and wires burnt at that location the following appliances were among the victims : refrigerator, microwave, range-oven, computer, monitor, modem, (CATV box, television, stereo, VCR in the next room). He mentioned that his insurance was $5K deductible. I think he's exceeded that. In addition to those problems I checked the breaker panel. Each neutral was landed on the ground bar along with its respective EGC under the same screw. Several (including the MWBC in question) were loose. I'm surprised this house didn't burn down.

$5k insurance deductible? Wow, I have a $100 and its common around here to be $500.00 but most insurance company's wont cover for faulty wiring, lightning yes, surge from power company maybe, but not from electrical problems within the home. good surge suppressors might have helped with some of those loads, and they would have had that guarantee to fall back on at least

 

[esox39]

I went on a similar call on Friday night. The guy was changing a old receptacle, the last one in line, and the neutral was wrapped around the silver screw then around the green screw. They were using the conduit as the neutral. Lost the microwave, stove, Xbox, TV, cordless phones. He also had to throw the power strips on the deck because they smelled so bad from burning up.

 

[jim dungar]

...back-stab the feed neutral into the receptacle (BTW, there were no GFI's in the kitchen). Wrapped around the screws were the neutrals feeding each of the two MWBC's.

Sounds like poor installation methods more than poor equipment design.

It is not the current HO's fault, too bad they have to bear the results.:weeping:

 

[growler]

Wrapped around the screws were the neutrals feeding each of the two MWBCs. Aside from the receptacle and wires burnt at that location the following appliances were among the victims : refrigerator, microwave, range-oven, computer, monitor, modem, (CATV box, television, stereo, VCR in the next room). He mentioned that his insurance was $5K deductible.

Around here you don't see many MWBCs in residential and it's probably a good thing. If a neutral opens on a branch circuit it's not a big deal just an open circuit.

With all the crappy wiring done by homeowners, handymen and home investors I can see this happening a lot if MWBCs were common practice in this area.

I went on a call some time back where the owner had ran a sub panel off the main and didn't even run a neutral to the sub panel. He burned up a few things. :happysad: You should have seen his face when I asked where was the neutral conductor.

 

[realolman]

....the rocket scientist who wired their kitchen decided to run a 12/3 RX to a kitchen counter JB and back-stab the feed neutral into the receptacle (BTW, there were no GFI's in the kitchen). Wrapped around the screws were the neutrals feeding each of the two MWBC's......

I don't see why he would be a "rocket scientist" for anything except 300.13 (B)

It doesn't seem to me to have anything to do with back stabbing or MWBC's

re the neutral and ground under the same screw

http://www.mikeholt.com/technical.p...&type=u&title=NEC - Question/Answers (1-4-2K)

 

[realolman]

I thought that the neutral had to be the only one under the screw and I see that 408.41 says that is true. I don't believe this was always the case, though..... NEC 2002 maybe?

 

[goldstar]

I don't see why he would be a "rocket scientist" for anything except 300.13 (B)

It doesn't seem to me to have anything to do with back stabbing or MWBC's

re the neutral and ground under the same screw

http://www.mikeholt.com/technical.p...&type=u&title=NEC - Question/Answers (1-4-2K)

Not sure I'm following you or who you're replying to. IMHO, if you were someone who customarily back-stabs receptacles the least you could do is wrap the feed neutral of the MWBC around the screw and then back-stab the outgoing neutrals. That way if one of those neutrals came out of the stab - no big deal - just an open circuit.

As far as neutrals and grounds being under one screw, this may have been a normal practice some years ago. However, if you stop and think about ther logic of that practice for a moment (and not focus on any NEC language), if there are 2 or 3 ground wires (all of the same size) under one screw and that ground bar indicates that it is approved for use for up to 3 wires then there is no problem. If one of those ground wires comes loose, while it may have some inherent dangerous affects it will not cause anything to burn up. On the other hand, if there were several neutrals under one screw and as luck would have it, if the neutral from a MWBC happened to come loose you would end up with the same scenario as in the OP.

 

[hurk27]

Not sure I'm following you or who you're replying to. IMHO, if you were someone who customarily back-stabs receptacles the least you could do is wrap the feed neutral of the MWBC around the screw and then back-stab the outgoing neutrals. That way if one of those neutrals came out of the stab - no big deal - just an open circuit.

Because 300.13(B) doesn't allow it.:happyno:

 

[Cow]

Because 300.13(B) doesn't allow it.:happyno:

The OP complains about shoddy installation practices and then suggests another code violation as a remedy.

Classic.

 

[realolman]

As far as neutrals and grounds being under one screw, this may have been a normal practice some years ago. However, if you stop and think about ther logic of that practice for a moment (and not focus on any NEC language), if there are 2 or 3 ground wires (all of the same size) under one screw and that ground bar indicates that it is approved for use for up to 3 wires then there is no problem. If one of those ground wires comes loose, while it may have some inherent dangerous affects it will not cause anything to burn up. On the other hand, if there were several neutrals under one screw and as luck would have it, if the neutral from a MWBC happened to come loose you would end up with the same scenario as in the OP.

I agree with you completely ....about the grounds and neutrals under the same screw... ... I was wrong.:dunce:

 

[weressl]

I went on a service call yesterday after a HO called said that on Xmas day they heard a pop in the kitchen and then started to smell things burning in several rooms. They began unplugging everything they could. Unfortunately.....they were too late. Some 15 or 20 years ago the rocket scientist who wired their kitchen decided to run a 12/3 RX to a kitchen counter JB and back-stab the feed neutral into the receptacle (BTW, there were no GFI's in the kitchen). Wrapped around the screws were the neutrals feeding each of the two MWBC's. Aside from the receptacle and wires burnt at that location the following appliances were among the victims : refrigerator, microwave, range-oven, computer, monitor, modem, (CATV box, television, stereo, VCR in the next room). He mentioned that his insurance was $5K deductible. I think he's exceeded that. In addition to those problems I checked the breaker panel. Each neutral was landed on the ground bar along with its respective EGC under the same screw. Several (including the MWBC in question) were loose. I'm surprised this house didn't burn down.

I am just wondering how the alleged loose wires caused the equipment damage?

 

[realolman]

now I know there is a hook to your question because I know you are extremely knowledgeable... but I'll bite to see what it is.

I don't know what damage it would or wouldn't cause but without the neutral, wouldn't the plugged in appliances act as voltage dividers across 220v according to their impedance.... which may or may not be healthy for some of them

 

[weressl]

now I know there is a hook to your question because I know you are extremely knowledgeable... but I'll bite to see what it is.

I don't know what damage it would or wouldn't cause but without the neutral, wouldn't the plugged in appliances act as voltage dividers across 220v according to their impedance.... which may or may not be healthy for some of them

He was talking about a SINGLE circuit and the associated neutral, unless there were other miswiring details that are not in the OP. On a single cable/circuit the broken neutral will cause open circuit, nothing else.

The 'voltage division' would involve a minimum of one of EACH leg of the transformer and associated shared neutral. The OP was talking about 12/3 RX, presumably phase, neutral and ground.

Were I the insurance adjustor, I would need more details.

 

[realolman]

....... Some 15 or 20 years ago the rocket scientist who wired their kitchen decided to run a 12/3 RX to a kitchen counter JB and back-stab the feed neutral into the receptacle (BTW, there were no GFI's in the kitchen). Wrapped around the screws were the neutrals feeding each of the two MWBC's. ...........




........Several (including the MWBC in question) were loose. I'm surprised this house didn't burn down.

I thought it was a MWBC ... but hey I'm wrong all the time

 

[jim dungar]

Were I the insurance adjustor, I would need more details.

I think you need to reread the OP. It said there was 12/3 BX feeding to a junction box. The neutral terminals of the back-stabbed receptacle served as the common point for several multi-wire branch circuits.

 

[gndrod]

The OP complains about shoddy installation practices and then suggests another code violation as a remedy.

Classic.

There is a conflict in the overall description. Reading MWBC hookup in the kitchen counter JB indicates there are other downstream room wiring from the kitchen. (violation #1) This job must have been bootlegged somewhere along the way. Any trouble shooting would be a mess especially with termination misapplications described.

To have all that equipment zapped at the same time would be a major system wiring fault to begin with. Having the neutral open then short to the other phase leg would be good for starters if the 'pop' emanated from the 12-3 MWBC kitchen JB and the EGC's stayed intact. This is just speculation of course.

 

[gndrod]

Because 300.13(B) doesn't allow it.:happyno:

I agree...a bad idea.

 

[George Stolz]

I've got something to say to those fools who use 18-2 for doorbells too - I saw a 4500W water heater on a 18-2 chime wire and it burned all the way through! :angel:

 

[gndrod]

I've got something to say to those fools who use 18-2 for doorbells too - I saw a 4500W water heater on a 18-2 chime wire and it burned all the way through! :angel:

Dang, I won't say another word about speculation.