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#94786 08/14/05 05:05 PM
Joined: Jan 2004
Posts: 1,507
JBD- Your no doubt right about the square D breaker - I've not been exposed to that breaker. You can bet our butcher talked about in this thread isn't using the right breaker. Thanks for the tip on the breaker.

George Little
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#94787 08/14/05 08:06 PM
Joined: May 2005
Posts: 706
Thanks JBD. I went to their website and these QO-H 2 pole breakers are available in 15-100 amp. I had previously thought that the high leg could only be used on three-phase loads.


#94788 08/14/05 08:23 PM
Joined: Jan 2004
Posts: 1,507
Two things:

1. Thats the nice thing about this forum, with all the banter that goes on there is always some very important information that comes along.

2. Good Contractor friend of mine will never install any 1Ø loads out of a 3Ø panel. He's probably making a good decision.

George Little
#94789 08/14/05 09:58 PM
Joined: Jul 2004
Posts: 9,766
Likes: 13
George, the problem in the <old> computer business was the single phase load might be behind a 3 phase plug. Some of our "3 phase" stuff was really an assortment of single phase power supplies and a few 3p motors. They also spec'ed line to line plugs on 3 phase panels as a normal course since we tried to never have any L/N loads in the computer room.
Even the small controllers and console terminals were 208/240.
In our delta vee computer rooms we had to monitor this closely.
Now that a "computer" is just a rack of PC boards I imagine that has all changed.

Greg Fretwell
#94790 08/16/05 05:51 PM
Joined: Feb 2005
Posts: 44
I have run across this on several occassions here in the old parts of town , small shopping centers, older restaurants, and large older houses. It was explained to me by some of the inspectors that this was due to the fact that when air conditioning was first invented that it required 3 phase 240volt power. Don't know if that is a fact as I never really researched it.
But I have had to follow behind a lot of electricians who didn't know and burned up a lot of appliances.
Just as a rule of thumb I always check the voltage on a circuit even when I think I know what it should be. This was beat into me by a former boss who didn't like buying equipment due to improper wiring.
Dave is right the good electrician will always admit his mistakes and sometimes as painful as they can be they are our best teachers.

#94791 08/16/05 10:21 PM
Joined: Mar 2005
Posts: 240
thanks guys for all your help.
it is nice to have a network like this that you can post things and get GREAT help and information from.


#94792 08/16/05 10:57 PM
Joined: Feb 2005
Posts: 693
Bogger, I have seen in some older (~1950's) houses with central A/C where a single #10 (I believe) was run parallel to the usual three-conductor drop, ran through the meter, and led to a disconnect that fed just the A/C unit.

Larry Fine
Fine Electric Co.
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