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Re: 220v circuit in garage

To: shop-talk@Autox.Team.Net
Subject: Re: 220v circuit in garage
From: "Douglas E. Shook" <dshook@usc.edu>
Date: Thu, 08 May 1997 23:58:15 -0400
You cannot argue with the "more is better" argument, but 100 amp service
requires #1/0 wire, and 200 amp requires #3/0.  This cable is not cheap,
is a hassle to work, requires major conduit, and gives you no advantage
unless you are drawing that kind of current.  It only takes a very basic
analysis of current draw to determine what materials are required.

As an example, a 5 hp, 220VAC compressor draws 15 amps, a standard 150+
amp arc welder draws 20 amps, each two tube shoplight draws .67 amps at
110 volts (if you are using the 40 watt tubes instead of the 25 watt
bulbs, which is a waste of electricity and natural resources).

So, let's assume your are running your arc welder and bead blasting the
same piece of steel concurrently at night with 10 shoplights (20 tubes)
running all at the same time (you would be a very busy man).  You would
draw 35 amps across the 220 legs and would draw an additional 3.33 amps
at 110 volts off each leg, or a total of 38.33 220 volt amps.  

Let's even get more serious, arc welding constantly in the winter, air
compressor running contantly, 20 tubes burning, and a 1500 watt 110 volt
electric space heater running contantly (this ought to warm up the
shop), you would consume about 50 amps. My own experience indicates that
constant concurrent operation of this scale is very rare.

At 50 amps, you can get by with #6 wire on a 105 ft. run with less than
a 2% voltage drop.

All I am trying to say is that you will never be caught short with a 200
amp service to the garage, but it may be similar to putting 105 octane
in an engine that will run on 89 octane--there is no value added, just
money consumed.  Use #6, use the change and take SHMBO out to a fine
dinner, or buy a set of good SK end wrenches or something else that you
will appreciate and use.

thank you,

shook
B50SS advocate

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