# Question about sharing a neutral



## ChunkyDrummer (Sep 16, 2014)

Hello all,
I have a quick question regarding sharing a neutral in a round house. Circuit 1 is a regular receptacle and circuits 3 & 5 is for a 208v motor. Can I share the neutral or will I need to pull two neutrals? 
Thanks


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## Fibes (Feb 18, 2010)

ChunkyDrummer said:


> Hello all,
> I have a quick question regarding sharing a neutral in a round house. Circuit 1 is a regular receptacle and circuits 3 & 5 is for a 208v motor. Can I share the neutral or will I need to pull two neutrals?
> Thanks


 If circuits 3 and 5 combine to make a 208V circuit why do you need another neutral besides the one for circuit #1?


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## mitch65 (Mar 26, 2015)

if cct 1 is 120 and cct 3 and 5 are for a (single phase) 208V motor, you should only need 1 neutral, no? what would the second one be for?


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## joebanana (Dec 21, 2010)

Just what would the other neutral be for?


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## Dennis Alwon (May 9, 2009)

ChunkyDrummer said:


> Hello all,
> I have a quick question regarding sharing a neutral in a round house. Circuit 1 is a regular receptacle and circuits 3 & 5 is for a 208v motor. Can I share the neutral or will I need to pull two neutrals?
> Thanks


One neutral and 3 hot conductors will work fine. This is not a round house since the neutral will only be for circuit #1. You have 2 branch circuits- one for the 120V and the other for the 208V. A full round or a full house would be where the neutral is shared between all 3 120V circuits.


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## Aegis (Mar 18, 2011)

Never heard of using the term 'full house' for a full set, interesting.


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## inetdog (Apr 13, 2016)

Aegis said:


> Never heard of using the term 'full house' for a full set, interesting.


Wouldn't a full house be three hots and a pair of noodles? :angel:


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## Dennis Alwon (May 9, 2009)

Aegis said:


> Never heard of using the term 'full house' for a full set, interesting.


I have also heard of a full boat


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## Dennis Alwon (May 9, 2009)

inetdog said:


> Wouldn't a full house be three hots and a pair of noodles? :angel:


Good one:thumbsup:


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## joebanana (Dec 21, 2010)

Dennis Alwon said:


> I have also heard of a full boat


That's the common term on the southern west coast. (except perhaps Mexico, and South America)


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## BSK3720 (Mar 29, 2014)

We used a full house for years, but the code now requires handle ties or a three pole breaker. It doesn't save money compared to pulling more whites and a three pole breaker for three 120 circuits confuses folks.


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## RePhase277 (Feb 5, 2008)

inetdog said:


> Wouldn't a full house be three hots and a pair of noodles? :angel:


No, a full house is Uncle Joey, Uncle Jesse, masculine Patriarch Danny, DJ, Stephanie, Rebecca, Kimmy Gibler, and the Olsons.


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## A-Z (Sep 10, 2016)

Why would you need a neutral for the 208v motor? From my experience they are usually treated as L1, L2 connections.


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## MechanicalDVR (Dec 29, 2007)

As others have asked; what is the neutral for in a 208v circuit?


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## Essex (Feb 4, 2015)

In the UK this would be unacceptable. Two live conductors and one common neutral? 

Would you be sizing the conductors to accommodate both motors running at the same time?


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## inetdog (Apr 13, 2016)

Essex said:


> In the UK this would be unacceptable. Two live conductors and one common neutral?
> 
> Would you be sizing the conductors to accommodate both motors running at the same time?



With a single phase 240V circuit (120-0-120) in the US the neutral will carry only the unbalanced current from the ungrounded wires and therefore will never be subject to more current than from one side alone. 
In the case of a three phase 208Y/120 circuit if identical current flows in two of the ungrounded conductors with a 120 phase difference the neutral will carry exactly the same magnitude current as each hot line. 

In the US we are not allowed to take two wires* from the same phase* with separate overcurrent devices and share a neutral.

The OP's reference to circuits 3 and 5 being for a 208V motor refers to one motor which is wired from line to line, with overcurrent protection on each line. No neutral connected to the motor. 
So in NEC parlance the two wires connected to _breakers _3 and 5 would be a single circuit, not two circuits.


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## PlugsAndLights (Jan 19, 2016)

BSK3720 said:


> We used a full house for years, but the code now requires handle ties or a three pole breaker. It doesn't save money compared to pulling more whites and a three pole breaker for three 120 circuits confuses folks.


No such code up here. Our code does require that the neutral connections
be such that devices can be replaced on any of the 3 circuits without 
opening the neutral. Seems sensible to me. No reason at all to require 
handle ties or 3 poles breakers. 
P&L


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## inetdog (Apr 13, 2016)

PlugsAndLights said:


> No such code up here. Our code does require that the neutral connections
> be such that devices can be replaced on any of the 3 circuits without
> opening the neutral. Seems sensible to me. No reason at all to require
> handle ties or 3 poles breakers.
> P&L


The NEC takes the view that even if devices can be replaced without opening the neutral (which is generally required), someone might open a bunch of neutrals marretted together in the process of extending a circuit or troubleshooting. Hence the same movement that disconnects one hot must disconnect them all. Common trip (in a two or three pole breaker) is not required, that is just one way to meet the requirement.


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## jdysart1 (1 mo ago)

On the west coast we call that a full boat


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