[Amps] what is a 4 wire 240VAC service?

[Martin A Flynn]

On 4/3/2011 3:33 PM, Paul Christensen wrote:
> "...All of the receptacles specified  for power
>> amplifiers are 3 wire, four pole grounding.  (NEMA L14-20R)"
> NEMA L14-20R is 3 pole, 4wire.
>
> "...he said he could not endorse an 2 wire, three  pole grounding (NEMA
>> L6-20R)  configuration due to liability reasons."
> And L6-20R is 2 pole, 3wire.
>
> Both locking receptacles utilize a ground conductor, so I don't know what
> liability the PE is referring to.  In any event, he did you the favor so
> that all new and most older commercial amps can be used -- although an
> L14-30R and 30A service would have been preferred if ever dragging a 77Sx
> into the shack.
My understanding is that he provided a neutral.  If  a user chooses not 
to use it and there is a negative outcome, the blame shift from him to 
the user.

BTW, the prints call out empty 3/4" conduit stubs running down the walls 
from the ceiling void on 3 of the 4 walls.   He may have already covered 
the option for additional circuits.

Martin