[TowerTalk] outlet ground problems and shack grounds updatinginfo needed please.

[jimlux]

Paul Christensen wrote:
>>
> 
> Also, check local codes on this.  I have to believe where primary use is for 
> two 120VAC in a residential installation, the practice of splitting phases 
> on a common neutral is prohibited in some areas.
> 

This is called a "multiwire branch circuit" and exhibit 210.2 in the 
2005 NEC shows an example of a split wired duplex receptacle with one 
half wired for 240V and the other for 120V.  The fine print note (FPN) 
talks about the necessity in such schemes for having a dual pole circuit 
breaker.

Another example given is the need to supply two appliance branch 
circuits for a countertop receptacle in a kitchen (And, now that I 
check, I see that's exactly what they've done under the sink in my 
house... one circuit for dishwasher, the other for the disposer, 
separate breakers).

The note says the neutral must be sized to carry 140% of the ampere 
rating of the circuit (220.61(A))

There's also special rules if you're using a 208/120Y or feeding 
nonlinear loads (solid state ballasts, switching power supplies)