# What size breaker?



## mopowers (Jul 20, 2009)

What size break is needed to run a 175amp 220v MIG welder? Wouls a 30amp breaker work?


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## jerryh3 (Dec 10, 2007)

Make and model number? Nameplate info?


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## 300zx (May 24, 2009)

10 Awg 30 *amp* *breaker*. *...* *A* *175*-180 *amp* *MIG* machine draws 19.5A max.


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## mopowers (Jul 20, 2009)

It's a Lincoln 175amp MIG. I don't have the welder with me.


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## mpoulton (Jul 23, 2009)

mopowers said:


> What size break is needed to run a 175amp 220v MIG welder? Wouls a 30amp breaker work?


Depends on the particular welder. The owner's manual will almost always tell you exactly what the recommended breaker and wire sizes are. Use them. A Millermatic 212 (150A machine) wants a 40A breaker on #10 wire. A Millermatic 251 (200A machine) wants a 60A breaker on #8 wire. Note that the wire size allowed is smaller than that normally permitted for the breaker - this is because the machine is duty cycle limited and functions as its own overload protection, like a thermally protected motor. The breaker essentially provides only short circuit protection, not overload. If you want to use the welder receptacle for anything else in the future, go ahead and run wire that is fully sized for the breaker instead.


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## Yoyizit (Jul 11, 2008)

Seems to me from previous posts that welders may temporarily draw more current than the steady-state breaker rating of 20A or 30A or whatever, but the trip curves of most breakers tolerates this.

These welders, like some chop saws, are pushing the limits of panel breakers. They want to advertise more welding power but not have the buyer put up with the expense of new wiring.


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## mopowers (Jul 20, 2009)

Well, I found the owner's manual and it says it recommends a 40 amp breaker and draws about 20 amps.

What happens if I run it on a 30 amp breaker?


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## Yoyizit (Jul 11, 2008)

mopowers said:


> Well, I found the owner's manual and it says it recommends a 40 amp breaker and draws about 20 amps.
> 
> What happens if I run it on a 30 amp breaker?


If you do short welds and allow the breaker to cool, you might get away with it. It also depends on the trip curve for your 30A. Post a link to your candidate breaker.

Your wire resistance will also provide some current limiting.

If you know the power in your arc you can work out the expected current drawn at the constant 220v.


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## mopowers (Jul 20, 2009)

Here is the breaker the electrician put in.

http://www.lowes.com/lowes/lkn?action=productDetail&productId=13538-296-HOM230CP&lpage=none

It's a double pole 30 amp. He used #10 wire.


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## 300zx (May 24, 2009)

mopowers said:


> Here is the breaker the electrician put in.
> 
> http://www.lowes.com/lowes/lkn?action=productDetail&productId=13538-296-HOM230CP&lpage=none
> 
> It's a double pole 30 amp. He used #10 wire.


Should be good.:yes: Post #3


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## mopowers (Jul 20, 2009)

300zx said:


> Should be good.:yes: Post #3


Even though Lincoln recommends a 40 amp breaker?


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## 300zx (May 24, 2009)

mopowers said:


> Even though Lincoln recommends a 40 amp breaker?


 draws 19.5A max why put on 40 amp with 10 wire?


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## 300zx (May 24, 2009)

To bad you don't have a Federal Pacific Electric panel .You would never have to worry about it tripping.(Just Joking) :laughing: I think you will be good.Will trip breaker if any problems.


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## Stubbie (Jan 7, 2007)

Don't you just love arc welders....


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## Stubbie (Jan 7, 2007)

mopowers said:


> Well, I found the owner's manual and it says it recommends a 40 amp breaker and draws about 20 amps.
> 
> What happens if I run it on a 30 amp breaker?



That's fine. The 40 amp breaker is simply the maximum breaker allowed. There is no code requirement that says you can't go to a lower amperage breaker. The main thing is that the breaker holds when you strike the arc and load the welder.

The branch circuit conductor ampacity must not be less than nameplate I-eff (effective current) or the rated primary current (I-Max) times the duty cycle factor of table 630.11(A). This gives you minimum ampacity. You then check table 310.16 for a wire in conduit or a cable assembly that is not less than that ampacity. You then take the table value of the conductors ampacity and multiply it by 2 to reach the maximum circuit breaker rating for the branch circuit conductors. If this value is not more than 200% (2x) of the I-max or rated primary current shown on the welder nameplate then the welder does not require integral (separate) ocpd.

40 amps max breaker for the branch circuit conductors suggests 20 amp I-eff or 20 amps for supply conductors after adjustments for duty cycle using primary rated current from the nameplate. 14 awg copper would be allowed to be used for this arc welder on a maximum 40 amp breaker unless specified by the manufacturer to be different.

In general for DIY residential use ... use the I-max (rated primary current) from the nameplate without adjustments to size your branch circuit conductors then stick the appropriate breaker in the panel. 50 amp I-eff or 50 amp rated primary current (I-max) = #8 awg copper in conduit or #6 nm-b cable with 50 or 60 amp breaker. This is just a rule of thumb used by many to avoid a mistake trying to follow art. 630.


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