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How many neutrals do you need? #33433
01/20/04 11:27 PM
01/20/04 11:27 PM
S
straightedge  Offline OP
Member
Joined: Mar 2002
Posts: 86
Mesa, AZ
I was working at a Best Buy here in Chandler, AZ, and was told to pull in the homerun wire to feed a Water Heater and an outlet only.

The building has 3-phase power. Circuit 24 is for the outlet and Circuit 25 is for the 120V Water Heater.

How many neutrals would you pull for circuit 24 & 25?

They are both 20-amp circuits and the water heater is rated at 1.7 KW.

The homerun wire is approximatly 150' away and I pulled #10 stranded copper thhn copper wire.

I pulled one neutral because circuit 24 is C-phase and Circuit 25 is A-phase.

I was told that I did it wrong. I should have pulled in two neutrals. Only consecutive groups can share neutrals. For Example: 2,4,6 ; 8,10,12 ; 1,3,5 ; 5,7,9

I stood up for my work and refused to aknowlege that I did something wrong.

Tev

Work Gear for Electricians and the Trades
Re: How many neutrals do you need? #33434
01/20/04 11:41 PM
01/20/04 11:41 PM
A
aldav53  Offline
Member
Joined: Aug 2001
Posts: 545
Chandler, AZ USA
One neutral should be fine.
I live in Chandler :-)
Al D


The Golden Rule - "The man with the gold makes the rule"
Re: How many neutrals do you need? #33435
01/20/04 11:46 PM
01/20/04 11:46 PM
S
straightedge  Offline OP
Member
Joined: Mar 2002
Posts: 86
Mesa, AZ
Thanks Aldav,

I just wanted to confirm that I was not missing something in the code book.

Re: How many neutrals do you need? #33436
01/21/04 12:16 AM
01/21/04 12:16 AM
H
hbiss  Offline
Member
Joined: Dec 2003
Posts: 886
Hawthorne, NY USA
...Only consecutive groups can share neutrals. For Example: 2,4,6 ; 8,10,12 ; 1,3,5 ; 5,7,9

Remind him that this is 3 phase NOT single phase.

Re: How many neutrals do you need? #33437
01/21/04 04:41 AM
01/21/04 04:41 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
No requirement to use consecutive breakers.

Just keep it on separate phases.

You are only using two hots of the 3 phase, this neutral will be a current carrying conductor when figuring for derating.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: How many neutrals do you need? #33438
01/21/04 05:55 AM
01/21/04 05:55 AM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,344
straightedge...
the only possible reason i can conjure would be if the 'outlet' were required to be afci protected.

other than that, people who tell you that something is 'wrong' are obligated to substaintiate thier claims

~S~

Re: How many neutrals do you need? #33439
01/21/04 07:33 AM
01/21/04 07:33 AM
S
straightedge  Offline OP
Member
Joined: Mar 2002
Posts: 86
Mesa, AZ
Thanks guys

Re: How many neutrals do you need? #33440
01/22/04 01:03 AM
01/22/04 01:03 AM
B
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
It's OK to do—just realize a couple of things.

For the neutral serving two phases derived from a wye system, for 20-amp 120-volt loads on different phases, there will be a full 20 amps in the neutral—making it a current-carrying conductor...one of three.

Regardless of phase selection, if for whatever reason two grounded-circuit conductors are used in the same cable or raceway with two ungrounded conductors, you now have four current-carrying conductors.

Re: How many neutrals do you need? #33441
01/22/04 09:33 AM
01/22/04 09:33 AM
W
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
I concur that running two _different phase_ hots and 1 neutral is to code. However IMHO it is slightly less safe, and it is possible that the _customer_ has requirements that exceed code and prohibit this particular installation.

If this documentation were provided ahead of time, and you missed it, then your installation was not correct, not because it didn't meet code, but because it didn't meet the customer's requirements. If they tell you this after the fact, then their specification was not correct; you put something in that meets code, and the customer wants something that exceeds code, but expected you to be a mind reader.

How is this installation slightly less safe? If the neutral opens then you will see a full 208V on the 120V receptacle. Is this a bad installation? IMHO it is fine. Multiwire branch circuits are a well accepted practise, are good enough for the NEC and are good enough for me [Linked Image]

-Jon


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