Branch circuit and plug size for welder.

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ashtrak

Senior Member
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Maryland
Could some one give me some advice.
I've never wired a welder before and someone asked me to wire theirs.
The info I got off the welder is a follows.
Century Mfg.
295 amp
Model 110-081
Primary amps 295
It has what looks like a 30amp 3pole plug with 10 wire sj on it now.
It will be used in a handy man type DYI operation ( home shop, in a garage) so duty cycle should not be an issue.
I'm looking at 630.11 and was wondering how I determine the duty cycle.

Thanks
 
131029-2114 EDT

It appears that Century has been purchased by Lincoln.

This is quite likely a small welder. 295 A input current makes no sense in that case. 295 A is probably an output current, and that will be at a considerably lower voltage. Maximum input current may not exceed 50 A, if that much. What is the input voltage? Contact Lincoln and see if they can help you.

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The welder will have a plate or sticker that should have the information you need.Im pretty sure 295A is output.
 
I would just supply the 30 amp receptacle with 30 amps and walk away.

I would not worry about duty cycle or any of that. If they shipped it with a 30 amp cord cap you can be sure it will work with 30 amps.

For what it is worth my own 250 amp output welder worked fine on a 30 amp supply.
 
iwire said:
I would just supply the 30 amp receptacle with 30 amps and walk away.

I would not worry about duty cycle or any of that. If they shipped it with a 30 amp cord cap you can be sure it will work with 30 amps.

For what it is worth my own 250 amp output welder worked fine on a 30 amp supply.
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I 100% agree if its a factory installed cord and plug, but I thought maybe the cord and plug were field installed.
 
steve66 said:
I 100% agree if its a factory installed cord and plug, but I thought maybe the cord and plug were field installed.
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That could be, in that case I would still likely forget about duty cycle and wire it at 100% of its rated input current.

The only advantage to using the duty cycle is to reduce the conductor sizing.
 
iwire said:
That could be, in that case I would still likely forget about duty cycle and wire it at 100% of its rated input current.

The only advantage to using the duty cycle is to reduce the conductor sizing.
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Yes and with a 30 Amp receptacle in a garage you can't reduce the conductor sizing anyway. They may plug in a big space heater or other appliance into this receptacle.


I agree with you, I don't install a welder I install a 30 Amp receptacle and they can plug whatever they want into it.
 
Thanks to all for your time Re: welder

Thanks to all for your time Re: welder

The welder in question has some age on it, and looks as though the cord and plug were added as opposed to a factory job.
I didn't want to spend the money on a manual but if thats what it takes to get the job done, oh well.
Of all the forums I looked in I didn't see anything on that model.
I saw one discussion that stated they were made for Sears, how true that statement is,I don't know.

Thanks to all for your time to answer
 
While I would normally agree with you guys about just wiring it for 30 amps, there are situations where that might not work out well (assuming it's an arc welder, anyway). For example, not long ago I came across a welder that comes with a 50 amp plug, but requires a 60 amp breaker. I thought there was a violation happening, until I came across:
210.21(B)(1) Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder shall be permitted to have an ampere rating not less than the minimum branch-circuit conductor ampacity determined by 630.11(A) for arc welders.
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So you could conceivably end up with a receptacle and conductors that are smaller than what would normally be allowed for your breaker.

Also, when dealing with arc welders, it's important to keep in mind 630.13.
630.13 Disconnecting Means.

A disconnecting means shall be provided in the supply circuit for each arc welder that is not equipped with a disconnect mounted as an integral part of the welder.

The disconnecting means shall be a switch or circuit breaker, and its rating shall be not less than that necessary to accommodate overcurrent protection as specified under 630.12.
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I'm not entirely sure what is meant by "a disconnect mounted as an integral part of the welder" -- I would guess that this is something more than just an on-off switch, but I don't really know and I haven't been able to find any specifics on what exactly is required. If there's no integral disconnect, though, (whatever that means) then note that this is one of those rare cases when the plug does NOT count as a disconnecting means -- there needs to be a switch or circuit breaker in addition to the plug.
 
JDBrown said:
While I would normally agree with you guys about just wiring it for 30 amps, there are situations where that might not work out well (assuming it's an arc welder, anyway). For example, not long ago I came across a welder that comes with a 50 amp plug, but requires a 60 amp breaker. I thought there was a violation happening, until I came across:

So you could conceivably end up with a receptacle and conductors that are smaller than what would normally be allowed for your breaker.

Also, when dealing with arc welders, it's important to keep in mind 630.13.

I'm not entirely sure what is meant by "a disconnect mounted as an integral part of the welder" -- I would guess that this is something more than just an on-off switch, but I don't really know and I haven't been able to find any specifics on what exactly is required. If there's no integral disconnect, though, (whatever that means) then note that this is one of those rare cases when the plug does NOT count as a disconnecting means -- there needs to be a switch or circuit breaker in addition to the plug.
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Look at the last two paragraphs of 630.12(A) [2011] and tell me if you do not think that they both say exactly the same thing. :blink:
 
GoldDigger said:
Look at the last two paragraphs of 630.12(A) [2011] and tell me if you do not think that they both say exactly the same thing. :blink:
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Haha, yeah. It was like that in the 2008 code also. It looks to me like they intended to re-word the paragraph, but forgot to delete the old version. I sure don't see any difference in what's actually being said in those two paragraphs.
 
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