Discuss Correct grounding of metal junction box w/splices for 3 circuits in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Noah Katz

DIY
Reaction score
3
I have 3 circuits (microwave, disposal, and dishwasher) entering a metal box where the THHN wire will be spliced to Romex.

I spent half an hour reading 2020 NEC Article 250 but didn't see multiple circuits specifically addressed.

To ground the box do I just need to pigtail off of one circuit's ground wire and attach to the box, or do I pigtail all 3 circuits' ground wires together?

In case you're wondering, the conduit is metal, which I believe is sufficient for grounding, but I don't trust all of the mechanical joints nor the fittings' set screws.
 
I have 3 circuits (microwave, disposal, and dishwasher) entering a metal box where the THHN wire will be spliced to Romex.

I spent half an hour reading 2020 NEC Article 250 but didn't see multiple circuits specifically addressed.

To ground the box do I just need to pigtail off of one circuit's ground wire and attach to the box, or do I pigtail all 3 circuits' ground wires together?

In case you're wondering, the conduit is metal, which I believe is sufficient for grounding, but I don't trust all of the mechanical joints nor the fittings' set screws.
Noah pig tail all the grounds to the box and you will be good
 
Cool, thanks.

Another question that I realize I need an answer to - should I pigtail all of the neutrals together?

I have a feeling NEC says no, but on the plus side, the extra copper would reduce voltage drop when less than full load capacity is being utilized, and it would be a wash if all circuits were fully utilized.
 
Cool, thanks.

Another question that I realize I need an answer to - should I pigtail all of the neutrals together?

I have a feeling NEC says no, but on the plus side, the extra copper would reduce voltage drop when less than full load capacity is being utilized, and it would be a wash if all circuits were fully utilized.

No, never join neutrals from different circuits together, this creates a very dangerous hazard for anyone working on the circuit in the future.
 
Cool, thanks.

Another question that I realize I need an answer to - should I pigtail all of the neutrals together?

I have a feeling NEC says no, but on the plus side, the extra copper would reduce voltage drop when less than full load capacity is being utilized, and it would be a wash if all circuits were fully utilized.
Yes you need to pig tail all the whites together also
 
They are from different circuits!!
If the THHN is the feed for the 3 appliances you would probably have 1 hot 1 neutral and one ground coming from the panel you would have to tie all the neutrals together. If 3 separate feeds that would be different. It sounds to me like all 3 appliances are on the same circuit. Noah how many THHN wires are do you have besides the 3 cables. I’m not saying it’s the proper installation, I’m saying it sounds like there all on the same circuit
 
If the THHN is the feed for the 3 appliances you would probably have 1 hot 1 neutral and one ground coming from the panel you would have to tie all the neutrals together. If 3 separate feeds that would be different. It sounds to me like all 3 appliances are on the same circuit. Noah how many THHN wires are do you have besides the 3 cables. I’m not saying it’s the proper installation, I’m saying it sounds like there all on the same circuit
I see your point OP needs to clarify.
 
If the THHN is the feed for the 3 appliances you would probably have 1 hot 1 neutral and one ground coming from the panel you would have to tie all the neutrals together. If 3 separate feeds that would be different. It sounds to me like all 3 appliances are on the same circuit. Noah how many THHN wires are do you have besides the 3 cables. I’m not saying it’s the proper installation, I’m saying it sounds like there all on the same circuit

I hope they are not all on the same circuit- that would overload a single circuit.

The OP could have two circuits sharing one neutral (MWBC) and in such a case yes all the neutrals would be tied together in the J-box. Make sure the breaker is a double pole, or both single pole breakers have their handles tied together.

If the OP has two or more circuits each with its own neutral coming from the breaker box then yes each neutral needs to be separate in the J-box.
 
I have 3 circuits (microwave, disposal, and dishwasher) entering a metal box where the THHN wire will be spliced to Romex.

I guess that is a bit ambiguous.

These are three separate circuits as required by 2020 NEC, each on it's own breaker, black/white/green THHN runs for each.

I'll keep the different circuits' neutrals isolated, and thanks westward10 and Dave for pointing out the hazard of doing otherwise.
 
I guess that is a bit ambiguous.

These are three separate circuits as required by 2020 NEC, each on it's own breaker, black/white/green THHN runs for each.

I'll keep the different circuits' neutrals isolated, and thanks westward10 and Dave for pointing out the hazard of doing otherwise.

Three separate circuits, 3 separate neutrals, we are all set! :)
 
After further thought, I realize I really don't see the hazard in pigtailing all of the neutrals together, since they're all connected together at the neutral bus bar in the panel.

What am I missing?
 
After further thought, I realize I really don't see the hazard in pigtailing all of the neutrals together, since they're all connected together at the neutral bus bar in the panel.

What am I missing?
Noah you are not missing nothing. The panel is the first disconnect after the meter and yes the neutrals and grounds can be terminated on the same bar. Any subfed panel after your main panel you have to separate the neutrals from the grounds
 
Any subfed panel after your main panel you have to separate the neutrals from the grounds

I'm not talking grounds vs. neutrals.

Two people said there was a hazard in connecting the neutrals from different circuits together.

They're already connected together at the panel neutral bar, so how is the hazard created?
 
I'm not talking grounds vs. neutrals.

Two people said there was a hazard in connecting the neutrals from different circuits together.

They're already connected together at the panel neutral bar, so how is the hazard created?
If you have more than 1 circuit sharing neutrals and you turn 1 breaker off to work on it the neutral will still have voltage on it from the other circuits sharing that same neutral. That’s the danger they are talking about
 
After further thought, I realize I really don't see the hazard in pigtailing all of the neutrals together, since they're all connected together at the neutral bus bar in the panel.

What am I missing?


A neutral that is supposed to be dead, would now be live to whom ever is working on it. This is not to code.
 
If the circuits are separate then keep the neutrals separate, joining them all together can create a hazard for anyone working on the circuits if they are not all isolated.

While it is not definitive, his first line is "I have three circuits..." I would take that to mean 3 individual circuits. If not, then I would expect it to be 1 circuit.

Paul
 
Hmm, I didn't get a reply notification; anyway

A neutral that is supposed to be dead, would now be live to whom ever is working on it. This is not to code.

How could a neutral be anything but dead when it's grounded at the panel?

Regardless, the crux of the matter which no one has addressed, is how it can make any difference if the neutrals are tied together at a junction box when they're already tied together at the panel.
[automerge]1590038053[/automerge]
While it is not definitive, his first line is "I have three circuits..." I would take that to mean 3 individual circuits. If not, then I would expect it to be 1 circuit.


I definitized it a bit later on:

These are three separate circuits as required by 2020 NEC, each on it's own breaker, black/white/green THHN runs for each.
 
Regardless, the crux of the matter which no one has addressed, is how it can make any difference if the neutrals are tied together at a junction box when they're already tied together at the panel.

In a normal circuit if a fault develops in the neutral then the circuit will stop working,someone will notice and get it fixed.
In your proposed arrangement if a fault develops in one of the neutrals the circuit will continue to work due to the other two neutrals being linked to it, however the fault will cause those two neutrals will be overloaded, but nobody will notice due to everything working. This overload could then lead, ultimately, to a fire.

Any GFCI (RCD) installed now or in the future to protect the circuit will trip instantly due to the imbalance caused by the joining of the neutrals.

Anybody working on the installation in the future will be unaware of this arrangement being in place, expecially considering it is specifically prohibited by your electrical code.
 

Reply to Correct grounding of metal junction box w/splices for 3 circuits in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock