Electrical Question

Friend has a shop that is wired with single strand run through conduit.

There are 3 20 amp circuits and 2 15 amp circuits.

The 20 amp are 12 gauge wire with only one 12 gauge neutral and one 14 gauge ground for all 3 20 amp circuits.

The 15 amp circuits are 14 gauge wire with only one 14 gauge neutral and shares the 14 gauge ground with the 20 amp circuits.

So to clarify a little there are 3 12ga hot wires,1 12ga neutral,2 14ga hots, 1 14ga neutral and 1 14ga ground to to service 5 circuits.

Question- Is there enough neutrals and grounds to service the 5 circuits? How many neutrals and grounds should there be?

Thanks

Gary

Gary;

No,there are not enuf nuterals. And increase the size of the ground wire to #12. It looks like he has 3 20 amp circuits and 2 15 amp circuits. He should have a nuteral with each circuit. 5 hots and 5 nuterals. Use the green as a redundent ground.

Stephen

That's what thought. Didn't matter much if only one circuit was used at a time, but he is going to have fans and compressors running at the same time now and I told him he was asking for trouble.

I told him I would help him pull more through the conduit. It's 3/4 conduit so he has the room.

Gary

Are you SURE there are Five (5) circuits?
It is not uncommon to share a neutral for 2 circuits. I have 6 circuits that I ran in my house through 1" conduit. 4 20 amp and 2 15 amp.
I used only 3 neutrals. I did not pull a ground wire. I had to get a permit and passed the electrical inspection 2 years ago.

Okay heres the deal: If you run a "branch circuit" out of a panelboard it should have its own black hot phase wire (protected by a circuit breaker), its own white Neutral (a grounDED conductor) plus a green/bare safety equipment ground. The Neutral is the return current conductor and is sized (ampacity) same as the hot phase conductor since its probably returning the same amount of amps.

IF YOU SHARE A NEUTRAL WITH TWO DIFFERENT BRANCH CIRCUITS THAT HAPPEN TO BE FED OFF THE SAME PHASE (Like L1 or L2) YOU CAN OVERLOAD THE WIRES AMPACITY RATING do not do that !!!!!!!!!!!!

For each branch circuit Id run a hot phase conductor and a Neutral AND NOTTTTTTTT USE A COMMON NEUTRAL FOR TWO DIFFERENT BRANCH CIRCUITS as you could overload the Neutral (if two circuits served by a single Neutral are on the same phase)

THAT BEING SAID There is such an NEC permissible thing called a "multi wire branch circuit" where a single common Neutral can indeed be used to serve as the return current conductor for two different phases BUT THAT IS NOTTTTTTTT A GOOD THING FOR LAY PERSONS TO MESS WITH AND NOT TO BE USED FOR HEAVY INDUCTIVE LOADS......

Soooooooo if I specified branch circuits out of a panelboard and ESPECIALLY for home shop use by lay persons I would insist each branch circuit have its own Neutral and would NEVER use any multi wire branch circuits (where single common Neutral serves two circuits)

NOTE I am long retired as an electrical distribution design engineer but can still safely say multi wire shared Neutral circuits should NOT be used for home shop type circuits. If theres 5 branch circuits Id have 5 hots and 5 Neutrals IM NOT SAYING IT CANT STILL WORK IM JUST SAYING IF YOU RUN A SINGLE COMMON NEUTRAL ON TWO CIRCUITS THAT HAPPEN TO BE ON THE SAME PHASE YOU CAN EASILY EXCEED THE WIRES AMPACITY.

If its a true multi wire branch circuit where each opposite phase carried say 16 amps the net Neutral current would be ZERO BUT YOU HAVE TO BE SURE THE NEUTRAL FEEDS TWO OPPOSITE PHASES

If I missed anything I hope the other gents can add to this but I would still run a Neutral for each branch circuit i.e. 5 branch circuits = 5 Neutrals (NO sharing).. Of course, 14 gauge wire is okay for a 15 amp branch circuit and 12 gauge for a 20 amp

John T Retired electrical engineer

It is code legal to share a neutral with two hots. But, the two hots must be on different busses and ideally should be on a two pole breaker. And the conduit can be used as ground. I know others may disagree but section 250.118 clearly states that conduit can be used as ground. I've done so with the local AHJ's blessing numerous times.

Youre RIGHT Have him run a Neutral for each branch circuit. Trying to use a common Neutral when the circuits may be on the same phase IS ASKING FOR TROUBLE See may post above

John T

This conduit is PVC. So the the conduit ground is out of the question here.

Gary

Thanks John T. That all makes sense to me.

Gary

"Common Neutrals" are allowed with some qualifications.

Not sure if it is NEC or a practice I have adopted since I can"t seem to locate it now, but I limit common neutrals to 2 adjacent "hot" wires thus if both circuits are in use the neutral actually has a smaller current in it due to the circuits being 180* out of phase. Same applies for 3-phase circuits.

Current code calls for common neutral circuits to be protected by a multi-pole breaker. Used to be able to use a handle tie.

Years back his building might have passed code and as such would be grandfathered in today, but as you make additions and revisions it should be brought up to current standards.

John T. said it so much better than I did. His reply was not there when I started mine.

A 2 pole breaker INSURES the hots are on two opposite phases, whereby the Neutral currents can cancel each other out NOTWITHSTANDING harmonics caused by inductive loads (i.e. do NOT use for high inductive circuit loads) .

Yep proper approved conduit can serve as an equipment groundING conductor provided allllllll the proper joints and unions and connectors are approved but its still NOTTTTTT a good thing for jack leg or amateur or lay persons to try to install or use, the NEC provides for safe minimum but thats NOT to say increased safety especially for amateur use isnt better. When I designed my boss would throw my design out the door if I left out bare/green safety equipmenmt grounds in lieu of relying on conduit lol BUT YOURE CORRECT IT CAN BE LEGALLY USED (just not if I were the designer or end user, I value some extra wire cost well worth my or my familys life)

YES it can be inspector approved, Im just saying its NOT how I choose to design, to each their own however no skin off my nose...

God Bless, fun discussion, thanks

John T

WE agreeeeeeeee, I like your addition of

"Current code calls for common neutral circuits to be protected by a multi-pole breaker. Used to be able to use a handle tie."

That insures opposite phases whereby Neutral current can cancel out

Fun chat, thanks

John T

If the service is three phase. Then one breaker each on the A,B & C phase. Then yes, one neutral is fine.
If this is a single phase service. The installer didn't have a clue or didn't care.

I'd add that I've seen conduit get bumped and bent. Over time, the tension from the bend pulls it out of a socket which may not be noticed. Then the ground is lost. Structures move and wood dries out over time and twists and warps, all of which can move conduit.

For the novice following this thread, a typical single phase breaker box has the busses alternate as you go down the box. That is why a double pole breaker on one side can give you 220/240 volts because it is tied into two separate buses. In Gary's situation if 3 20 amp breakers were stacked together in a breaker box sharing a neutral, then the top and bottom ones would be on one buss and the middle on another buss. Gary would have to check to see how the breakers are spaced in the box as well as if there is 3 phase or not.

Exactly but you wouldn't believe how many cheapskates will tell you. That conduit or the sheath of flexible makes a suitable ground conductor.