On Sat, 26 Jun 2010 23:02:26 -0700 (PDT), Vernon
wrote:

Guys,

I am building a heavy "extension cord" intended to carry 50 amps not
more than 100' from our 200 amp power box to my van. Inside the van
will be a couple of welders and a plasma cutter.

Vernon..can I make a suggestion? Instead of using your van..aquire or
build a small Wells Cargo type trailer or even a homemade trailer.

It is pretty common around these parts to do just this, and thats one of
the reasons Ive got a 5x8 Wells Cargo tucked away in the side yard. It
will be converted to a portable workshop sometime this summer, a bench,
grinder, enclosed storage etc etc.

Its easy to simply add outdoor outlets to either the walls just inside
the back doors, or actually mount them outside on the walls.

Just a thought.

Ive run into too many situations where during the middle of the job,
Ive had to run somewhere to pick up something and had to unhook all
manner of Stuff, or pull my helper off the job because I took his tool
"shed" to the store with me.

Gunner


The idea will be to move the van around the yard to where I need to do
welding or cutting so that I don't have to load and unload the
equipment constantly.

I am running AWG #4 four conductor wire. The power supply end of the
cord will plug into a 4 conductor (two hots, ground, and neutral) 50
amp plug protected by a 50 amp breaker located at the main power box.

The cord will terminates at a 100 amp weatherproof box that is screwed
to a 4' piece of 2x12. This "panel board" will be semi-permanently
affixed to the interior of the van - perhaps fastened to the back of
one of the bucket seats.

The panel box only has spaces for three 240v circuits. One of these
three will be a 50 amp plug controlled by a 50 amp breaker inside the
panel box. Another will be a 20 amp 220v circuit for my inverter
welder. It's the same plug configuration as for a 220v air
conditioning unit.

I wish to use the last of the three spaces for 2 pole circuit breaker
energizing a two gang box that will have two duplex 120v receptacles
(i.e. four 120v receptacles).

Rather than put these 120v plugs on 120v single pole breakers I would
prefer to split each leg of the double pole breaker to feed two of the
outlets.

I believe I'm correct that every time you double the voltage you
reduce the amperage by 50%?

Does this mean that a 20 amp double pole breaker will give me 40 amps
of 120 volt protection? In other words, if I have 4 outlets (two on
each leg) protected by a single 20 amp breaker will each duplex 120v
receptacle be good for 20 amps?

Also, from a code standpoint is it permissible to protect more than
one circuit by the same breaker? In other words, and by way of
example, is it kosher to run a single 240v plug PLUS two 120v outlets
by simply doubling up the hot wires under the breaker lugs?

Since I work alone it is not gonna happen that I'm using the inverter
welder and any 120v power tool at the same time. I just wanna know if
anybody remembers what the codes say about this and can give me a
title reference. To the extent that it is not inconsistent with good
electrical practice I would prefer to have enough outlets mounted on
the panel board to keep all of the equipment permanently plugged in -
or at least one of the big welders AND the plasma cutter. That would
save me having to crawl in and out plugging and unplugging machines.

Finally, should I ground the truck frame to the box?

Thanks,

Vernon

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch