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Re: [Shop-talk] 220 outlets

To: "'David C.'" <>, "'Mark Andy'" <>
Subject: Re: [Shop-talk] 220 outlets
From: "Paul Mele" <>
Date: Wed, 29 Jul 2009 05:48:18 -0400
I know that there are lots of other authorities on this, but here's one

cut a 6 inch piece of wire, i.e. "pigtail", splice it and the incoming and
outgoing together with a wirenut.  a little practice with the wide-jawed
electrician's pliers and you can get the 3 12g or 10g wires to twist into a
nice spiral; then clip off the end at 45 deg (perpendic. to the axis of the
twisted strands.  this makes a nice point to feed into the wire nut.
the free end of the pigtail goes to the device (outlet).

as far as the rating on the outlets goes, recall that the job of the breaker
in the box is to limit the current thru the wiring (in the wall) to the
rated carrying capacity of the wire, e.g. 12g/ 20 A, 10g/ 30A (each wire
gauge has a rated ampacity; it is determined by the amount of heat given off
by the wire when it carries max amperage; this in turn prevents fire
potential in the walls).  you can always use a load (lamp, welder, motor)
which draws or needs less amperage than the rated ampacity of the wire.  The
wire stays cool, no fire hazard.  Of course, if you always use a bigger than
needed wire, you waste money.
the job of the outlet/ device is to limit the load placed on the wire in the
wall.  you don't want to plug in a 20A load into a circuit with 14g  (15A
ampacity) will overheat the wire.
so, in the current scenario, a 20A 220V outlet attached to an 8g wire (40A
ampacity) would simply limit you to plugging in a 20A load...the 8g wire is
fine with that. So is the breaker, whose job is to protect the wiring and
the house, not the load (e.g. welder) .  The load would be protected by its
own internal breaker as determined by the engineer who designed the load.
an 8g wiring run to a (pair of) 40A breakers with multiple 20A / 220V
outlets would allow you to plug in all the tools you'd like, and run any 2
at a time.  
there is no difference with this arrangement as compared to several 15A/ 110
outlets on a 12g 20A breaker circuit...the total load to the circuit breaker
(and heat from the 12g wiring) doesn't care how many 110V loads are will trip if you try to run too much current thru the wire and
burn down the house.

that said, 2 thoughts...
8g wire is stiff...have fun.  there are special wire nuts for these babies.
the wire gauge examples/ ratings are for runs less than 75 feet (if memory
serves); consult the tables, but expect to go up one size if you go 76 to
150 ft, e.g. 10g wire to carry 20A 120ft, if memory serves.

HTH; others may do a better explanation.


Yeah, 220 outlets aren't designed to daisy chain like 110 outlets are. 
What I have done  is use a 2x4 or 4x4 handy box as a splice box and run 
two or three circuits out of that, but, as you said, splicing gets kind 
of messy.  The big wire nuts are rated for 3 or 4 conductors, and the 
wire rating is usually on the package or sometimes actually on the wire 
nut itself.  I am looking for a cleaner way to do this, too.  I'm 
starting to lean towards the sub panel idea and will be pricing sub 
panels at the Borg sometimes in the next few weeks.  If there is some 
way to use a buss system instead of a splice box I would like to hear 
about it.

> The issue I've had with this kinda thing is how to splice the (thick)
> wires together to be able to put a bunch of 220vac outlets in series.
> Love to get any feedback on proper methods for this.
> Also, if you size the breaker big enough for two loads, remember that
> the outlets all need to be rated for that higher amperage as well, which
> almost certainly means redoing plugs, etc.
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