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[DPRG] Way off topic - home wiring

Subject: [DPRG] Way off topic - home wiring
From: Randy Carter rwcarter.wa at netzero.net
Date: Sat Jun 18 22:46:30 CDT 2005

A GFCI will work with only the hot and neutral wires connected.
It wants the current in both the neutral and hot wires to be
within 500uA of each other.  They are the only actual signals
monitored.  The ground is mainly for the 3rd pin and is only used
for the GFCI test function.

As for the unusual voltage potentials I don't have a clue.  But
keep in mind digital VOM's have a very high input impedance and
they can pick up AC hum easily.  The neutral, ground and conduit
are supposed to be connected to the earth ground at the breaker
box.  The age of your wiring could also be a factor, they didn't
do things the same way in the past.

Try testing your outlets with one of those plug in testers.  They
look like a large plug with 3 lamps on the end.  They are
relatively inexpensive and available at just about every hardware
store.

> Karim Virani wrote:
> Sorry bout this - but I didn't know where else to ask.
> 
> I was trying to replace an external 120 outlet with a new GFCI receptacle.  I was measuring the voltage potential and ran into a problem.  The voltage between the neutral and hot was just fine at 120.  But the voltage between hot and the bare ground wire was 80v, neutral and ground was 40v. So I tried to short between ground and the other 2 wires separately - no substantial current flowed.
> 
> Even stranger - the box and conduit are metal, so I checked the potential there:
> box to ground wire = 30v
> box to hot = 80v
> box to neutral = 2v
> 
> Now I'm very confused.  I can see how a high-resistance short between ground and hot could cause the ground/hot/neutral relationship, but the box/hot/neutral relationship seems baffling.  And how likely is a 30v differential between a bare copper wire and the conduit it's running through?  Gremlins?
> 
> I don't expect a GFCI would work with just hot and neutral connected?  And no I don't want to burn my house down or fry the next guy to fiddle with that outlet.
> 
> I guess it's time to hire an electrician to pull fresh wires.
> 
> Thanks,
> 
> Karim
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