Correct grounding of metal junction box w/splices for 3 circuits

[Noah Katz]

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.

 

[Megawatt]

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

 

[Noah Katz]

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.

 

[westward10]

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.

 

[davesparks]

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.

 

[Megawatt]

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

 

[westward10]

Yes you need to pig tail all the whites together also

They are from different circuits!!

 

[Megawatt]

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

 

[westward10]

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.

 

[Cookie]

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.