[Shop-talk] unsafe wiring

[Pat Horne]

Chris,

If you are comfortable working in the electrical panel that feeds the 
sub-panel you can replace the double breaker there with a single one and 
connect the remaining wire which used to go to the breaker to the 
neutral bus. This will give you 120V on one hot, a neutral and a ground. 
If you are not comfortable doing this, see if you can find a friend or 
neighbor who is.

Short term, just remove one of the wires from the output of the dual 
breaker and put it onto the neutral bus. I suspect that one of the wires 
is white, so that is the one that should go to the neutral bus with all 
the rest of the white wires.

If you want to add a GFCI, you can, but many times motor powered stuff 
(especially older motor stuff) will cause the GFCI to trip, so I 
wouldn't expect it to work all that well.

As for the difference in potential between neutral and ground, there 
shouldn't be any. The two should be tied together in the main service 
panel, but I don't recommend using the safety ground for normal current 
carrying duty, it wasn't designed for that.

Peace,
Pat

Thusly spake Chris Kantarjiev, On 5/10/2009 4:41 PM:
> I need to do something that I know won't be quite right, and want to figure
> out how to do it as safely as possible.
>
> I have a sub-panel that feeds (fed) the heatpump - it's fed with three
> conductors: both phases, and ground. The heatpump has been dead for at least
> 15 years; two owners back installed a swamp cooler right above it.
> The previous owner left behind the extension cord that he used to
> power the swamp cooler, and I've done the same thing for several
> summers - but I've had enough. 
>
> I know that I can get 125v from one phase to ground. I also know that this
> isn't quite kosher, since there may be some voltage drop from
> real ground to this phony neutral. I think that means I should use
> a GFCI, and that will be reasonably safe - am I understanding this
> correctly?
>
> Or will the GFCI just keep tripping? :-)
>
> Is using BX cable outdoors a reasonable thing? It appears to be what
> was used to go to the heatpump, but I don't think of BX as being
> weathertight. This is all under the roof eave, but still...
>
> Thanks.
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-- 
Pat Horne, Owner, Horne Systems 
(512) 797-7501 Voice		5026 FM 2001
Pat at HorneSystemsTx.com	Lockhart, TX 78644-4443
www.hornesystemstx.com
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