[Shop-talk] Electrical Outlet wiring question

[Peter J. Thomas]

On 3/12/2010 5:44 PM, Steven Trovato wrote:
> Peter,
> I don't think that is correct.  My house has two outlet circuits wired 
> with a single run of 14-3 Romex and a 220 breaker.  Some outlets use 
> one side of the 220, some use the other.  But they all use the common 
> neutral.  This was reasonably common practice to save wire, and met 
> the code, at least 25 years ago when my house was built.    Besides,  
> I don't think the loads add the way you say.  In fact, because they 
> are out of phase, they cancel out.  This is why you try to balance the 
> load between the two sides of the 220 at the panel.  DISCLAIMER:  I am 
> not an electrician.  I can speak with authority on how my house was 
> wired, but I'm not an authority on the National Electric Code, or 
> whatever codes apply to where you live.
I had a conversion on 220 and phase difference with a licensed 
electrician some while ago and the topic of shared neutral came up.  He 
denounced the practice sharing a neutral.   I understand the phase 
difference cancelling and even asked him about it.  He insisted it was a 
bad practice, and IIRC said he had seen failures.  Just thought I would 
share the warning he gave me.

>
> -Steve Trovato
> strovato at optonline.net
>
> At 05:16 PM 3/12/2010, Peter J. Thomas wrote:
>> Do not use a common neutral.  Each outlet needs is own common return.
>> If you use a 20A duplex break and 12 gauge 3 wire (4th wire bare 
>> ground) romex (rated 20A IIRC) and install 20A outlets, the two hot 
>> leads will be protected to 20A but a common return could be carrying 
>> 40A if you plug in 2 20A loads, twice the rating for 12 gauge.
>>
>> Peter Thomas