Thread: Where are the Circuir Ground Conductors?

This is a branch distribution panel (1 of 2 within the home) with approximately 2-dozen or so breakers/circuits and only four circuit ground conductors (a single 12-gauge conductor has been run with 20 or so circuit conductors). There is a large (8"x12"x12") junction box within the attic where these ground conductors have been spliced together...I'm being asked to provided a reference as to why it's mentioned in the report.

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It appears the wire is run in conduit. If so, no ground wire would be required if the conduit is metal as the conduit could serve the purpose. If a ground wire is present only one ground wire is required per conduit and it has to be as large as the largest circuit conductor. As long as the box in the attic is large enough for all the wires present (this one is good for 500 or so #12s) it would be OK to have all the grounds spliced together in the box. Short of this being a bussbar or terminal strip of some type it's not likely that anything else would be listed for a large number of wires. Unknown from your description is whether the wiring method after the J-box is NM-B or conduit so not sure what's happening there.

Probably of more concern is the wire size and breaker rating as this is a prime spot for derating based on conduit wire fill. 20 current carrying conductors would require a 50% derating and this would mean a 15 amp circuit would require a #12 wire, and this even before ambient temperature derating was done.

Anyway, assuming the connections for the grounds are OK in the J-box (and the wire is large enough for the circuit size) the single #12 ground in the conduit is a non issue.

I'm betting the wire size IS an issue.

Thanks Bill. Non-metallic cable is run from the attic junction box to each fixture. In 12 years and 5000+ inspections I've never seen this before and I've never seen an junction box this big.

Originally Posted by Bill Kriegh

Probably of more concern is the wire size and breaker rating as this is a prime spot for derating based on conduit wire fill. 20 current carrying conductors would require a 50% derating and this would mean a 15 amp circuit would require a #12 wire, and this even before ambient temperature derating was done.

I'm betting the wire size IS an issue.

Needed repeating and emphasis added to the derating for ambient temperature as those conductors run into the attic, thus ambient temperature would be required.

Looks like there is probably 25 current carrying conductors (not counting the white conductors as I suspect they are shared neutrals for multiwire circuits); 21-30 current carrying conductors derates to 45% of the ampacity for derating; you are in Long Beach California so you probably have attic temperatures of 130 degrees (give or take, and that give or take affects the derating factor, if the attic temperature never exceeds 131, the derating factor is 0.76, if the attic temperature is between 132 and 140, the derating factor is 0.71, but let's go with 0.76); let's presume those are 90 degree C rated insulation conductors (trying to give the best end rating possible).

The ampacity for derating for those conductors is 30 amps, times the ambient derating factor of 0.76 equals 22.8 amps, times the derating factor for the number of conductors of 45% equals 10.26 amps, which means the largest breaker allowed for those circuits would be 10 amp breakers.

And that is the BEST CASE scenario.

Just an awesome post Jerry...Thanks.

Originally Posted by Marc Morin

Thanks Bill. Non-metallic cable is run from the attic junction box to each fixture. In 12 years and 5000+ inspections I've never seen this before and I've never seen an junction box this big.

I'm trying to envision a 8x8x12 with all these circuits entering it and then outgoing nm with egc's . I would love for you to post a picture(s).

Do you know what code cycle (2002, 2005 ...)was enforced when this resourceful wiring took place??

This home was a major remodel in 2006 and no, I didn't get a photo of the large j-boxes. They were obviously listed boxes with lots and lots of knock-outs with all wiring routed neat and tidy. Yeah, a picture would be nice....

Originally Posted by Marc Morin

This home was a major remodel in 2006 and no, I didn't get a photo of the large j-boxes. They were obviously listed boxes with lots and lots of knock-outs with all wiring routed neat and tidy. Yeah, a picture would be nice....

I was asking about the code cycle as there are some issues if you have multiwire branch circuits sharing neutrals as Jerry suspects (me too) originating in your pictured panel.

It's always nice to see good workmanship as you state but still doesn't mean that the installation is compliant. I would like to see the jb with the cover off cause I've just got one of those feelings .....

One time when I found a big junction box in an attic, it was due to a fire in the garage which had burned up the E panel. The electrician cut off all the burnt ends and made a couple of dozen splices in the attic J box.

Originally Posted by Roger Frazee

I was asking about the code cycle as there are some issues if you have multiwire branch circuits sharing neutrals as Jerry suspects (me too) originating in your pictured panel.

It's always nice to see good workmanship as you state but still doesn't mean that the installation is compliant. I would like to see the jb with the cover off cause I've just got one of those feelings .....

Well, I deferred the whole thing for review by an electrician so there you have it...thanks for all the posts!