Multi – Multi wire branch circuits - Electrician Talk - Professional Electrical Contractors Forum

Gravy · 01-20-2010, 04:21 PM

I am looking for the specific code that prohibits a single oversized grounded (neutral) conductor when you are installing multiple full boats.

For example a 3 phase panel 120/208 with two (20 amp/ckt.) full boats (six ungrounded conductors) what prohibits me from running a single #8 awg grounded conductor as opposed to two #12’s?

I have talked with a couple of guys here at work and the best we can come up with is that it is simply bad practice but I would like to be able to cite a specific code it violates. I’m still looking into this so if I find something before I get any responses I will post them here. Thanks for your help.

raider1 · 01-20-2010, 04:29 PM

You won't find a specific code section that prohibits what you described.

But, 2008 NEC section 210.4(B) requires a means to simultaneously disconnect all ungrounded conductors of a multiwire branch circuit. It could be rather tough to find a 6 pole breaker or an identified handle tie for 6 single pole breakers.

Chris

Gravy · 01-20-2010, 04:36 PM

Interesting way of looking at it - I hadn't thought of it that way.

I 'spose sharing a neutral would make all of the ungrounded conductors part of the same MWBC.

Good on ya!! If you're a drinker and we ever cross paths the first round is on me

brian john · 01-20-2010, 04:39 PM

Local terminology? - FULL BOAT = ?

brian john · 01-20-2010, 04:41 PM

Quote:

Originally Posted by raider1

You won't find a specific code section that prohibits what you described.

But, 2008 NEC section 210.4(B) requires a means to simultaneously disconnect all ungrounded conductors of a multiwire branch circuit. It could be rather tough to find a 6 pole breaker or an identified handle tie for 6 single pole breakers.

Chris

Long 1/8" toggle bolt will do the trick on some CBs.

**Speedy Petey** · 01-20-2010, 04:47 PM

Unless you ran #8 neutrals to EVERYTHING tap rules would also come into play. No?

brian john · 01-20-2010, 04:51 PM

Quote:

Originally Posted by Speedy Petey

Unless you ran #8 neutrals to EVERYTHING tap rules would also come into play. No?

I would not do as the OP is suggesting (in the past or now), but not sure where you are heading with your post?

NolaTigaBait · 01-20-2010, 04:52 PM

Quote:

Originally Posted by brian john

Long 1/8" toggle bolt will do the trick on some CBs.

I was thinkin about a long nail

Bob Badger · 01-20-2010, 04:56 PM

Quote:

Originally Posted by Gravy

I am looking for the specific code that prohibits a single oversized grounded (neutral) conductor when you are installing multiple full boats.

For example a 3 phase panel 120/208 with two (20 amp/ckt.) full boats (six ungrounded conductors) what prohibits me from running a single #8 awg grounded conductor as opposed to two #12’s?

I have talked with a couple of guys here at work and the best we can come up with is that it is simply bad practice but I would like to be able to cite a specific code it violates. I’m still looking into this so if I find something before I get any responses I will post them here. Thanks for your help.

Actually NEC specifically allows that for outdoor circuits.

I do have to ask how you think that would work out money wise by the time you deal with bigger boxes and wire connectors.

raider1 · 01-20-2010, 06:10 PM

Quote:

Originally Posted by brian john

Local terminology? - FULL BOAT = ?

Yeah, "Full Boat" is a local slang term for a multiwire branch circuit that is run in a raceway.

Usually in my area a full boat is A,B & C phase with a neutral and an EGC of the wire type where specified.

Chris

raider1 · 01-20-2010, 06:11 PM

Quote:

Originally Posted by Gravy

Interesting way of looking at it - I hadn't thought of it that way.

I 'spose sharing a neutral would make all of the ungrounded conductors part of the same MWBC.

Good on ya!! If you're a drinker and we ever cross paths the first round is on me

Next time I'm in Minnesota I will look you up.

Chris

william1978 · 01-20-2010, 06:24 PM

Quote:

Originally Posted by brian john

Local terminology? - FULL BOAT = ?

I never heard it called that till a few weeks ago and the guy that used that term said it was B,R,Bl,W or B,O,Y,G.

brian john · 01-20-2010, 06:47 PM

Quote:

Originally Posted by raider1

Yeah, "Full Boat" is a local slang term for a multiwire branch circuit that is run in a raceway.

Usually in my area a full boat is A,B & C phase with a neutral and an EGC of the wire type where specified.

Chris

Well I learned something today, so waking up was not a waste.

We call it a multi-wire branch circuit.

knowshorts · 01-20-2010, 07:24 PM

"Full boat" is used in SoCal also. I forgot what I used to call it.

**MDShunk** · 01-20-2010, 09:11 PM

I've heard full boat as referring to any 5-wire circuit.

**480sparky** · 01-20-2010, 09:17 PM

Full boat to me means three hots and a noodle on a three-phase system. Ground is whatever you're using for ground.... conductor or pipe.

Adam12 · 01-20-2010, 10:57 PM

Quote:

Originally Posted by 480sparky

Full boat to me means three hots and a noodle on a three-phase system. Ground is whatever you're using for ground.... conductor or pipe.

We commonly use the term "full boat" around here too. Meaning what 480 described.

eddy current · 01-24-2010, 08:20 AM

Round here we use the term "full set" to describe one conductor of each phase and a neutral.

DERITM · 01-24-2010, 12:08 PM

"Networks" in Chicagoland.

InPhase277 · 01-24-2010, 12:50 PM

We call them "full sets" or "networks" as well. I never heard the term full boat until I read it on some electrical forums.