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Old 07-09-2012, 07:47 PM   #16
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MIG Welder Electrical Supply Circuit Specs


So according to the CEC the smallest you can go wire size is 19.6A but when you derate for 80% you find you need tens at minimum. It's a 200% increase in breaker size so the biggest breaker you can use is either 200% of the max amps of the unit OR 200% of the allowable ampacity of the wire your using. Whichever is smaller.

the long an short of it is you were A ok with what you said in your original post. As for the receptacle size the cec say's nothing about going bigger, only that you can't have a receptacle on a branch circuit rated at less than the overcurrent protection.

I always like to cover my butt though so i would probably use the 30A breaker to protect the wire but your good to go either way.

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Last edited by andrew79; 07-09-2012 at 07:50 PM.
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Old 07-09-2012, 09:21 PM   #17
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MIG Welder Electrical Supply Circuit Specs


I get 67A while the arc is struck and with a 40A breaker with this trip curve
http://static.schneider-electric.us/...0600DB0105.pdf
an arc lasting longer than 70 to 400 seconds would trip the thing.

Last edited by Yoyizit; 07-09-2012 at 09:24 PM.
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Old 07-09-2012, 10:18 PM   #18
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MIG Welder Electrical Supply Circuit Specs


Well all I can say is my MIG welder is 240VAC @ 21A (120A 20% duty cycle welding current at max setting) and I have never tripped a 15A branch breaker.
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Old 07-10-2012, 09:52 AM   #19
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MIG Welder Electrical Supply Circuit Specs


Quote:
Originally Posted by andrew79 View Post
So according to the CEC the smallest you can go wire size is 19.6A but when you derate for 80% you find you need tens at minimum. It's a 200% increase in breaker size so the biggest breaker you can use is either 200% of the max amps of the unit OR 200% of the allowable ampacity of the wire your using. Whichever is smaller.

the long an short of it is you were A ok with what you said in your original post. As for the receptacle size the cec say's nothing about going bigger, only that you can't have a receptacle on a branch circuit rated at less than the overcurrent protection.

I always like to cover my butt though so i would probably use the 30A breaker to protect the wire but your good to go either way.
andrew79: I was just woindering where you came up with the 19.6 Amps? Where in the code?
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Old 07-10-2012, 10:14 AM   #20
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MIG Welder Electrical Supply Circuit Specs


36a full load times .55, you have to use the full load amps not the calculated duty cycle amps to get your new wire size. Standard rule is you can only load to 80% for any wire or breaker not rated for 100% use. So you need wire capable of handling 19.6/4*5 which gives you 24.5a. Might want to double check that as I don't have a calculator handy.
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Old 07-10-2012, 10:40 AM   #21
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MIG Welder Electrical Supply Circuit Specs


The welders specifications actually show the full load amps at 20 Amps, so applying the 80% rule to that number would make it 25 Amps. #10 is okay.

Thanks again for your help.
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Old 07-10-2012, 11:21 AM   #22
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MIG Welder Electrical Supply Circuit Specs


Quote:
Originally Posted by curiousB View Post
Well all I can say is my MIG welder is 240VAC @ 21A (120A 20% duty cycle welding current at max setting) and I have never tripped a 15A branch breaker.
21A x 100%/20% = 105A which is a 7x overload for a 15A breaker.
Using the same trip curve, you might get away with it if your arc duration is less than 2 to 8 seconds.
Or maybe your breaker contacts are welded closed.

Sounds like I'm going to be e-mailing welder makers for an interpretation.
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Old 07-10-2012, 12:08 PM   #23
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MIG Welder Electrical Supply Circuit Specs


Quote:
Originally Posted by Yoyizit View Post
21A x 100%/20% = 105A which is a 7x overload for a 15A breaker.
Using the same trip curve, you might get away with it if your arc duration is less than 2 to 8 seconds.
Or maybe your breaker contacts are welded closed.

Sounds like I'm going to be e-mailing welder makers for an interpretation.
I think you should be dividing by 0.80 (80%) and not 0.20 (20%). IF the welder was drawing 105 amps at 240VAC on the input side, the current on the output or secondary side (i.e. the Arc) at 34 volts would be huge (>750 AMPS)!!

The welding current is more in the order of 130 amps based on the specs of my welder.
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Old 07-10-2012, 02:03 PM   #24
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MIG Welder Electrical Supply Circuit Specs


Quote:
Originally Posted by Yoyizit

21A x 100%/20% = 105A which is a 7x overload for a 15A breaker.
Using the same trip curve, you might get away with it if your arc duration is less than 2 to 8 seconds.
Or maybe your breaker contacts are welded closed.

Sounds like I'm going to be e-mailing welder makers for an interpretation.
It's 21A on 240VAC side, 120A at welder tip. Breaker is fine, I've tripped it with a space heater or two (before N gas furnace added) and I've switched off power a few times.

130A welder is only 9% higher than 120 so if a 15A @240V is working fine for me I can't imagine why a 40A is needed or advised. But that's just me.
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Old 07-10-2012, 02:32 PM   #25
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MIG Welder Electrical Supply Circuit Specs


Yes but were talking about the op's welder which has rated current not full load amps. His fla is 36a. None of my replies were ever directed towards you. The 19.6a is from the conductor size you can use which is found by taking the Fla at a factor of .55 for a 30% duty cycle.
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Old 07-10-2012, 05:36 PM   #26
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MIG Welder Electrical Supply Circuit Specs


The company responds without answering my question and without directly saying that they refuse to answer my question.
The generator companies that I asked are going the same way.

". . .will draw 20 Amps of current at rated welding output. The rated output of this machine is 130 Amps @ 20 Volts when used at the 30% duty cycle on a 230 Volt AC supply."

130Ax20V = 2600W = 11A @ 230V
???

Maybe if I learned Japanese I could finally talk to a factory applications engineer.
These marketing people should have been politicians; the money's better and they can probably have all the women they want.

Last edited by Yoyizit; 07-10-2012 at 05:47 PM.
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Old 07-10-2012, 06:15 PM   #27
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MIG Welder Electrical Supply Circuit Specs


Quote:
Originally Posted by Yoyizit View Post
The company responds without answering my question and without directly saying that they refuse to answer my question.
The generator companies that I asked are going the same way.

". . .will draw 20 Amps of current at rated welding output. The rated output of this machine is 130 Amps @ 20 Volts when used at the 30% duty cycle on a 230 Volt AC supply."

130Ax20V = 2600W = 11A @ 230V
???

Maybe if I learned Japanese I could finally talk to a factory applications engineer.
These marketing people should have been politicians; the money's better and they can probably have all the women they want.
Yes there is some funny rating going on here and it seems like safety factor after safety factor over applied. Sure it enhances safety but with seemingly no regard to cost.

The welder is basically a current transformer stepping down the 240VAC to roughly 24 VAC (about 10:1) and then passing the AC through a bridge rectifier and a capacitor. That will bring DC to the Open Circuit voltage of 34 as specified in the specs. (1.4x pickup, AC RMS to DC).

Working backwards then if the welding current is 130A and it is going through a 10:1 transformer then the current on the 240 VAC must be around 13A. Why they specify a 40A slow response breaker is beyond me. As for the initial current surge upon striking the arc, that seems to be the job of the electrolytic capacitor after the bridge rectifier.

It smells to me like cascaded conservative assumptions. As a result users are spending more on wire that really needed. It also explains why my 120A welder never trips a 15A @ 240VAC circuit.

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