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Re: Shop breaker box question

To: Mark Andy <>
Subject: Re: Shop breaker box question
From: Brian Kemp <>
Date: Tue, 09 Aug 2005 19:32:10 -0700
Mark - I'm assuming this panel is wired as a subpanel off the house.  If 
so, you should have a circuit breaker in your main panel that turns all 
power to the outbuilding on and off.  If this breaker is about 2 inches 
wide and has two wires coming off it, your outbuilding is wired for 
220V.  If it has just one wire from the breaker, the building should be 

I saw your later post about getting an electrician to help connect 
things.  In your case, I think that is a great idea. 

To do a sanity check on the quality of work in your subpanel, verify 
that the ground and neutral come in on two different wires are are not 
connected within the subpanel.  Neutral should be white, ground is 
likely to be bare or green.  The only place they should be connected (in 
the majority of applications) is in main breaker box of the house.  If 
you have one wire in the subpanel that serves as both the ground and 
neutral, chances are an electrician didn't do the work and you need to 
have the whole electrical system looked at.  This is a safety issue.  
Ground should always be ground.  Since the neutral wire carries current, 
there is the potential for a voltage differential over the wire.  In a 
long run and high current situation, it could be enough to cause a 
problem by elevating 'ground'.

I read a bunch and thought this was all common sense (after you research 
it).  I was surprised when the spa delivery guy asked me who wired the 
subpanel for the spa.  I told him I did and asked what was wrong.  He 
said nothing, it was the first panel of 5 he saw that day that was 
actually wired properly.

A web search for subpanel, ground, and neutral should get you the same 

Brian - not an electrician, well trained

> Check your incoming feed wire to the box.  You should have three... 
> One to each hot lug in the box, one to the neutral/ground.  If you 
> _do_ have all three, check for voltage between them all... You should 
> have 110vac between either hot lug and the neutral, and 220vac between 
> the two hot lugs.
> My guess is that one of your hot lugs is either missing or is wired to 
> the neutral in the feed box.
> Again, remember that the incoming wires are always hot, no matter what 
> the position of the main breaker.

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