Subject: elec. wiring f/welder

From: [email-masked] (Rooster)
Date: Tue, 23 Apr 1996 19:30:11 GMT

My arc welder has a NEMA 6-50 plug, and uses (of course) the
corresponding receptacle.  The plug is about $13, the recept. about $10.
An electric range usually uses a 10-50 plug and recept., and these cost
about 1/3 of the 6-50's.

Can I refit 10-50's to my stuff safely?  I'm never going to plug a range
into the arc welder outlets, not unless my wife puts a wheel kit on the
Amana.

Thanks for any info.
---
 þ OLX 2.1 TD þ my other car is a Deutz Allis 9190
                                                   
-- 
rooster

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From: [email-masked] (Burr Fontaine)
Date: 25 Apr 1996 02:34:33 GMT

In article <[email-masked]>, [email-masked] says...

Rooster:

I usually tap my brother-in-law electrician/electrical inspector for answers 
to questions like this.  The following are his comments mixed with some of 
mine:

First of all, your welder may be unsafe for a number of reasons, but it 
certainly won't be safe unless the frame or cabinet is adequately grounded.

The National Electrical Code for most connections to a branch circuit requires 
that the neutral and equipment ground wires be kept separate and carried as 
separate wires back to the circuit breaker box where they then are connected 
together.  Until January 1996 the code contained an exception (sec 250-60) for 
120-240 volt, 3-wire branch circuits for electric ranges and electric clothes 
dryers that allowed the neutral to be used for both neutral and frame ground 
provided the grounded circuit conductor was not smaller than No.10 AWG.  The 
NEMA 6-50 plug is a 4-wire, 50 amp plug that uses a separate connector for the 
equipment ground, and, if my memory is correct, the 10-50 plug is a 3-wire, 50 
amp plug that uses the white, neutral, conductor for both equipment ground and 
the neutral conductor.  Since both plugs are rated at 50 amps, 240 volts, the 
current rating is not a problem.  However, since the code only granted the 
single wire exception for neutral and frame ground to ranges and dryers and 
not welders, your use of a "range" outlet for your welder, strictly speaking, 
would not meet the requirements of the code.

Since January 1996 the National code has deleted the exception for ranges and 
dryers and now at the national level requires separate ground and neutral 
wires to be brought back to the circuit breaker box, i.e. a 6-50 plug with 
four separate wires.  Since this is in a state of transition, the code 
authorities in your location may or may not have changed to the new rules.

Regards, Burr

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From: [email-masked] (Bob Powell)
Date: 27 Apr 1996 23:07:45 GMT

The comment about requiring a 4-wire plug for 120-240V devices is correct,
but does not apply to welders.  Welders are 240V only and do not require
a neutral connection because they draw no current between hot and ground/
neutral.

The reason ranges and dryers have a different 3-prong plug for the same 
apparent voltage and current as welders is because they are 120-240V
devices and the welders are not.  The range/dryer plugs have a beefier
ground prong because it is actually carrying current, whereas the welder
plug is just a normal roung ground prong not a wide flat blade.  Seems to 
make sense.  

(With dryers, typically the only component that actually uses the 240V
is the heating element; the timers, maybe even the motor are 120V.  Likewise
with ranges the lights (ever see a 240V lightbulb?) and fans, at least,
are 120V.  With 240V welders everything runs off transformers that have 
240V primaries.)

There's no functional reason you couldn't use the cheaper plug and outlet
for the welder, but it would not meet code.  I suppose the outlet itself 
would meet code if it had the appropriate size current-carrying ground/neutral.

In article <[email-masked]>, [email-masked] says...

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From: [email-masked] (Burr Fontaine)
Date: 30 Apr 1996 16:02:18 GMT

In article <[email-masked]>, [email-masked] says...
>would meet code if it had the appropriate size current-carrying 
ground/neutral.
According to the pictures of plugs and receptacles in my Grainger catalog, a 
NEMA 6-50 is a 2-pole, 3-wire device and not the 4-wire device that I guessed 
it to be.  So, if that is what the manufacturer of your welder recommends, 
your welder is definitely a 250v unit and does not require 120v from the house 
service anywhere in its operation.

I agree with Bob that there is no functional reason you couldn't use either 
the 6-50 or the 10-50 plugs and receptacles with your welder, but if I were 
doing it, I'd want the receptacle that's permanently added to my house wiring 
to meet code.  In the 6-50 case this would mean using two #10 wires for the 
current conductors and the appropriate size ground wire for connection to the 
ground pin of the receptacle.  (10-2 romex with ground is not commonly 
available so if you buy 10-3 with ground the white wire is tapped up and not 
used.)

If you use the cheaper NEMA10-50 receptacle, it should be wired as a 50-amp 
range circuit, i.e. all three #10 wires are connected to the current carrying 
pins of the receptacle.  If the receptacle is mounted on a metal box, the 
ground wire is used to ground the box.

Burr

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From: [email-masked] (Burr Fontaine)
Date: 30 Apr 1996 16:31:59 GMT

In article <[email-masked]>, [email-masked] says...
>... In the 6-50 case this would mean using two #10 wires for the 
>current conductors ...

I also said a few non-repeatable things as I read the screen again after
pushing send, but it was too late!! 

    A 50-amp circuit requires #6 wire and not #10, sorry. Burr