I was looking to wire a welder in a residential garage. The primary voltage is 230v at 131 amps. The homeowner does not need to use the welder at full power. Would it be fine to wire the welder with 100 amp overcurrent protection and #2 conductors which will handle the amperage?If the homeowner were to draw to much current it would trip the CB. The homeowner fully understands this. If it were a industrial place, I would obviously wire it at the max amperage. Is it safe to underrate the OC protection? Reason for not wirng this at max current is that there is only a 150 service.
wiring a welder
- Thread starter otm126
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- Bremerton, Washington
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- Master Electrician
Re: wiring a welder
Welders have a duty cycle, the small little buzz boxes may be only 20%,so the size of the branch circuit is derated by the duty cycle. The duty cycle is the number of minutes out of 10 that the welder can be used. The higher the duty cycle the bigger the transformer, and the larger the branch circuit is.
The answer to your question is in Section 620.11 of the NEC.
Welders have a duty cycle, the small little buzz boxes may be only 20%,so the size of the branch circuit is derated by the duty cycle. The duty cycle is the number of minutes out of 10 that the welder can be used. The higher the duty cycle the bigger the transformer, and the larger the branch circuit is.
The answer to your question is in Section 620.11 of the NEC.
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: wiring a welder
Would recheck the amps.Sounds way to high for residential, have seen a few that take 50
Would recheck the amps.Sounds way to high for residential, have seen a few that take 50
Re: wiring a welder
Thanks for all the input. This is an industrial welder that will eventually go into a commercial garage. It is a temp install for a residence.I took notice to the current rating but not the duty cycle. My mistake. Thats the reason for this question. I will probably not do the job because I am not all familiar with welders.
I see that you can size the OC for 200% so I now understand how a 30 amp CB could draw 100 amps current. Thanks again!!!
Thanks for all the input. This is an industrial welder that will eventually go into a commercial garage. It is a temp install for a residence.I took notice to the current rating but not the duty cycle. My mistake. Thats the reason for this question. I will probably not do the job because I am not all familiar with welders.
I see that you can size the OC for 200% so I now understand how a 30 amp CB could draw 100 amps current. Thanks again!!!
Re: wiring a welder
If it is a commercial unit, there is a good chance it could draw 130 amps with close to 100% duty cycle. You might want to be cautious as POCOs tend to severly limit the size of a welder that can be run off a residential service. I don't recall off the top of my head but I think there are also limits to the size of a branch circuit that can be installed in a residential occupancy. I've got a welder of that class in my garage but I just wired it with a 50 amp pigtail and provided a 50 A circuit with a receptcle for it. If somebody ignores me and cranks up the dial past halfway, it will just trip the breaker. Any way you look at it, it is a can of worms.
If it is a commercial unit, there is a good chance it could draw 130 amps with close to 100% duty cycle. You might want to be cautious as POCOs tend to severly limit the size of a welder that can be run off a residential service. I don't recall off the top of my head but I think there are also limits to the size of a branch circuit that can be installed in a residential occupancy. I've got a welder of that class in my garage but I just wired it with a 50 amp pigtail and provided a 50 A circuit with a receptcle for it. If somebody ignores me and cranks up the dial past halfway, it will just trip the breaker. Any way you look at it, it is a can of worms.
mikeames
Senior Member
- Location
- Gaithersburg MD
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- Teacher - Master Electrician - 2017 NEC
Re: wiring a welder
Just to clairify a 30 am bkr cant allow 100 amps the welder is an xfr that changes voltage thus changing primary current/ secondary current. The primary may be under 30 amps and the secondary at 100 but the voltage is not 120 or 240.
Just to clairify a 30 am bkr cant allow 100 amps the welder is an xfr that changes voltage thus changing primary current/ secondary current. The primary may be under 30 amps and the secondary at 100 but the voltage is not 120 or 240.
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