[AT] Wire size for welder?? Help welder people!

[Larry D. Goss]

Well said, Dean.  There's another item to be considered also.  I went
through building and wiring a new shop a couple of years ago and had the
problem of wiring an outlet for a welder.  I put in #6.  It's about the
same size as a garden hose and just about as flexible as a hose with 40
lbs of water pressure inside it, but I fished it around through the
boxes and got it installed.  Since I did the wiring myself, I had to get
a permit and have it inspected before the contractor would touch the
construction to install insulation and other finishing details.  It
passed inspection and the job got completed, but that's not the kicker
-- A year or so later, it came time for renewing my homeowner's
insurance and since there had been quite a number of changes (new shop,
new kitchen, etc) I had to provide evidence of having passed the
electrical inspection since it was not done by a licensed contractor.
Otherwise, the property would not have been insurable, or at least would
not have been insurable by the company I've been with for better than 25
years.

I had a central air-conditioner in the house where I lived in Oklahoma
that got temperamental after five or six years of use and it got so it
wouldn't start on super-hot days.  I looked at the specs on the
nameplate and it specified #10 wire for an electrical run of up to 25
feet, larger for anything beyond that.  The run was almost exactly 25
feet.  The repairmen had tried everything else to make the air
conditioner work right and nothing helped, so I went down to TSC and
bought a length of #8 wire, pulled it through the conduit as I pulled
out the #10, hooked it up, and never had another problem with the
compressor stalling on start up.

Larry  

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Dean VP
Sent: Wednesday, December 08, 2004 2:53 PM
To: 'Antique tractor email discussion group'
Subject: RE: [AT] Wire size for welder?? Help welder people!

Greg:


Your suggestion of wire size IMHO is pushing the limits of common sense.
Unless one knows that John is going to be normally welding at less than
maximum output all of the time, #10 gauge wire is inadequate for the job
and
will eventually or almost immediately cause some problems. The 25' run
comes
into play here heavily. We also don't know the incoming wiring size to
the
breaker or the rating of the overall supply. Just too many unknowns
require
one to select higher than may be minimally required. The cable getting
warm
is just a small part of the problem. What will affect performance of the
welder is voltage drop. Now if the nominal 220v supply is already low
then
additional voltage drop in the 25' cable, breaker and connections will
even
be more noticeable. 

As an old and now obsolete EE and one who designed many electronics
circuits
and products in the early years of his career including power supplies,
it
is very important for long term reliability and safety, to over design a
bit. When one worst case tolerances circuits and allows all worst case
variables to happen at once it is amazing what the real circuit
requirements
are. For example if a resistor has to nominally dissipate 50 Watts.
Design
in a 100 watt resistor. Safety is always the primary concern and then
long
term reliability. It is never wise to skimp on wire size when hooking up
to
a welder which costs 10 to 20 times what the wire costs not considering
what
the building it is in costs. 

Let me provide an example, I personally experienced, what the cost is of
an
under designed electrical circuit could be.  This is in the mid 60's. I
was
sent to Lockheed Martin Marietta, GA to help get customer acceptance of
a
$7,000,000 Hybrid Computer facility that my company had sold and
installed.
I had been responsible for a portion of the design but not the total
system
design. 

Upon entering the computing facility late one evening when the computing
lab
was vacant, all 4 analog computers and one digital computer were running
but
not being used, I noticed an unusual smell.  To this day I remember the
smell and I said to my escort:  "I smell Allen Bradley".  The smell of a
Carbon resistor over heating is very unique!  There was row after row on
large 6' tall cabinets all filled with electronic equipment. It was an
air
conditioned room and the smell seemed like it was everywhere. We
frantically
opened door after door trying to find the location of the source of the
smell. Eventually, I opened one door and flame shot out over 4' high.
Fortunately we were able to contain the damage to one cabinet. 

I spent another 3 1/2 weeks getting the system repaired and accepted but
we
really wanted to know why this had happened. Upon returning to the lab
at
the home office we did a detailed design analysis of the purchased
commercial power supply that had been the cause of the fire. After much
analysis we determined that one underrated resistor in the design was
being
overstressed and the body of the resistor had been mounted in contact
with
the Printed Circuit Board. The resistor had gotten so hot that it lit
the
PCB on fire. This was in the days when fire resistant PCB's were not
commonly used like they are today. But here was the case where the
circuit
had not been properly worst case designed. A lousy $0.50 or $2.00
resistor
could wipe out a $7,000,000 facility along with a potential hazard to
human
life. I have never forgotten that lesson. 

I am probably known as being very frugal on this list but when it comes
to
this kind of stuff, I will spend money freely to avoid endangering
facilities and humans. In this area it does not pay to try to "just get
by"!

BTW, all of these Power Supplies were immediately replaced in all
installed
systems. Ok, rant over!  :-)


Dean A. Van Peursem
Snohomish, WA 98290

I'm a walking storeroom of facts..... I've just lost the key to the
storeroom door 


www.deerelegacy.com

http://members.cox.net/classicweb/email.htm



-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Greg Hass
Sent: Tuesday, December 07, 2004 9:00 PM
To: Antique tractor email discussion group
Subject: Re: [AT] Wire size for welder?? Help welder people!

John:

At the risk of being arrested by the "correct police", I will give what
I 
consider to be a "common sense" approach.
First of all, that amperage rating is only at the very top end of the
usage 
scale.  I have a 150-amp wire welder and a 250-amp AC/DC stick welder.
I 
have been running both of them on a no.10 wire since I built the shop 10

years ago, and have never had a problem with the wires getting warm, 
although I did use a 50-amp breaker (on the advice of a licensed 
electrician) to take care of the sudden amperage jolt when striking an 
arc.  A big thing in my favor, however, is that my biggest run is 25
feet 
from breaker box to welder.  If you are already wired for a welder, I
would 
say go ahead and try it because if you are properly fused the worst that

could happen is that you would trip a breaker or blow a fuse.  I would 
guess that most of the welding jobs you would do would draw less than 30

amps anyhow.  If you want to be correct, I would go with a no. 6 copper
or 
no. 4 aluminum entrance cable or Romex, whichever it's called in your 
area.  (Aluminum must always be one size bigger than copper to carry the

same amperage.)  No. 8 copper would be sufficient for 45 amps, however
in 
our area it is next to impossible to find and costs more than no.6,
which 
is why I recommended going with the heavier cable.  Just an opinion.

Greg Hass

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