Thread: Neutral CCC

I understand that the neutral can be a CCC, but havent seen it (the far back conductor) hotter than the hot conductor, ever.
This was taken at an inspection, well actually, while on an inspection a neighbor asked me to scan her panel, so I was only there for 2 minutes and sorry no information avail. I do know that the only load imposed was the bathrooms ceiling light, she said. Just an unusual anomaly.

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Improperly wired MWBC?
Resistance due to a poor connection?

Kinda what I thought too. Honestly, just wanted to go home after long 5 hour inspection, my brain was fried & dogs were barking.

I'd be really surprised if that amount of heat was generated off just a ceiling fan, you'd think there would be some discoloration at the white wire termination to indicate a hot-spot.

Can't really tell from your photo but if I saw that, I'd also look to see if that was a neutral off a 3-wire circuit, perhaps both hots are on the same phase causing the neutral to carry the sum-total amps of both circuits

ie: red wire draws 12 amps (normal)
blk wire draws 12 amps (normal)
white wire carries 24 amps (problem)

If breakers (on 3-wire example) are on correct & opposite phases, the white wire amps in the above example would be 0

I agree...I think I will go back over to look into this. Pretty interesting. Would a bathroom circuit be a 3 wire?

Originally Posted by Marc M

I agree...I think I will go back over to look into this. Pretty interesting. Would a bathroom circuit be a 3 wire?

They might have pulled 12/3 with one leg feeding the required 20A GFCI protected receptacle and the other leg feeding lights/fans/etc.

Curious as to why she wanted you to look at her panel though. What did she suspect?

Originally Posted by Corn Walker

They might have pulled 12/3 with one leg feeding the required 20A GFCI protected receptacle and the other leg feeding lights/fans/etc.

Curious as to why she wanted you to look at her panel though. What did she suspect?

Man...! She was the definition of DIY. She just said here bathroom was just remodeled and she was watching over them and she said they seemed like total hacks. So , she saw me scanning a panel and recognized the camera from HOMES ON HOMES or whatever, and asked me if I wouldn't mind checking her panel.
She is going to email me the results after the electrician looks at it. I will post them here.

Originally Posted by Marc M

I understand that the neutral can be a CCC, but havent seen it (the far back conductor) hotter than the hot conductor, ever.
This was taken at an inspection, well actually, while on an inspection a neighbor asked me to scan her panel, so I was only there for 2 minutes and sorry no information avail. I do know that the only load imposed was the bathrooms ceiling light, she said. Just an unusual anomaly.

Yes, it's a visible anomaly but how hot is it? I scan panels all the time and it is not unusual to see one wire that shows "hotter" than the others. It's relative to the other wires and the range that the IR camera is set to. Unless it exceeds the temperature of the wire rating, it may not be a big issue. Getting a temperature reading off something as small as a 12 ga wire is difficult since it does not fill the target spot and is therefore inaccurate.

The anomaly only points out "a potential problem" and that there's more to do to diagnose this like using a clamp-on amp meter etc.

As a Thermographer, doing so would far exceed the scope of work you are supposed to be doing. When I scan commercial panels, there is always a qualified electrician there to open and close the panels and follow up on any findings. Per my insurance company, I'm an "Industrial Photographer" and am not acting as an electrician.

Originally Posted by Joe Klampfer

I'd be really surprised if that amount of heat was generated off just a ceiling fan,

You'd be surprised.

For some reason it is MUCH more common for the neutral conductor to burn up that a hot. I have seen this many times and on circuit that are not always heavily loaded.

More often than not it is not an improperly wired MWBC, but a poor connection to the neutral bar. Funny thing is I almost never see it in cases where more than one neutral is terminated in the same hole or where a neutral and ground are terminated together. Typically it is a complaint single neutral in a hole that burns up.
Weird.

Originally Posted by Dana Bostick

Yes, it's a visible anomaly but how hot is it? I scan panels all the time and it is not unusual to see one wire that shows "hotter" than the others. It's relative to the other wires and the range that the IR camera is set to. Unless it exceeds the temperature of the wire rating, it may not be a big issue. Getting a temperature reading off something as small as a 12 ga wire is difficult since it does not fill the target spot and is therefore inaccurate.

The anomaly only points out "a potential problem" and that there's more to do to diagnose this like using a clamp-on amp meter etc.

As a Thermographer, doing so would far exceed the scope of work you are supposed to be doing. When I scan commercial panels, there is always a qualified electrician there to open and close the panels and follow up on any findings. Per my insurance company, I'm an "Industrial Photographer" and am not acting as an electrician.

Completely correct...I see wires which are waaay warmer than others all day long that are not of issue. GFIs, AFCIs, pool pumps, A/Cs, etc under load. But this is a neutral. Not very typcial in residential scans.

DIYers replacing a Single pole switch with a combination device, wiring error in a lighting/switch loop where power from the panel was at the light, or wiring error switching the neutral (light wired backwards).

See errors a lot in 2-wire (with or w/o ground) switch loops by DIYers and "Handy" types who don't identify where power from the panel is, esp. who are unfamiliar with older non-re-identified conductors in switch loops - power at the light, switch, or preceeding j/b.

Would be interesting to note at the shell of the light fixture - if it has been wired backwards. Test shell see if it is energized.

Is there a combination gfci single receptacle and single pole switch in the bathroom now? or just a SP switch and a combination gfci/duplex receptacle? Combination switch (two switches - one for fan?) Was there anything plugged into the receptacle? was it wired to just protect the face?

Was the light fixture one with a regular resistive edison type lamp? a compact fluorescent lamp? a compact LED lamp? a low-voltage fixture with its own power supply/step down transformer? Regular single pole switch? dimmer? Low-voltage dimmer? fixture have a fan? speed control?

Loose connection at new light fixture box or at switch/receptacle box even wirenutted neturals behind switch might have been dislodged (high resistance connection), forcing lots of 12 gu. into tiny single or 2-gang plastic box without much room esp. crammed in without accorian folding (prefer using deeper boxes and larger ones with reducing plaster rings) can dislodge connections.