What size circuit for a welder?

[BBQ&Love]

I am wiring my shop and want to put in a circuit in case I ever want to pug in a welder.

1. I have enough 8/2 w/ground and a 40 amp breaker on hand.

2. I have a small shop (14x24) and will never do heavy duty fabrication work there.

3. If I buy a welder, it will most likely be a fairly small MIG. I cannot fathom any need for a heavy welder and if I do need one, I have access to a couple nearby.

4. The path to upgrade later is not a huge deal. It would involve removing an access panel and running some conduit on the outside of the wall (under my workbench). It isn't what I want, but it could be done.

Shall I put in the 40 amp circuit and be done with it? Or spend the $120+ it will cost to put in a 50 amp circuit?

 

[Aceman]

You should be fine with the 8-2 and 40 amp breaker.

 

[John in OH]

If you look at the specs for a typical small MIG welder, such as a Hobart Handler 187, you will find that the input to the primary side of the machine is 20.5 amps at 240volts at rated load. So you should be fine with a 40 amp feed.

On a historical note ... back in the 1950s-60s, the Rural Electrical Authority (REA) that served rural areas of America, established a maximum single point load limit of 40 amps for any given load at a farm. At this time, stick welders were growing in great popularity in the US so to address this 40 amp limit, most welder manufacturers designed and sold a simple transformer-type welder (buzz box) that required a maximum input of only 39 amps. These machines gave a maximum secondary (welding current) output of 180 amps. At 180 amps you can do some serious stick welding!

So, even if you choose to go with a stick machine you could still use the 40 amp circuit ... assuming you could find a used 180 amp welder on eBay or at an auction somewhere. As far as I know, this old REA limit no longer exists and I don't know of any manufacturers that still make a 180 amp machine ... but I have not researched the subject.

 

[Strouty]

I have a large miller shopmaster 300 amp and it only uses a 80 amp circuit. I think you will be fine with 40.

 

[John in OH]

22rifle ... I just took another look at your original post and now note you are proposing to use 8/2 with ground cable (I assume this is a bare ground).

A cable with only 2 conductors and a bare ground will work OK if the welder is a purely 240 volt load, but if the welder you purchase also has any 120v accessories or drives you will need a cable with 3 conductors and a ground. In the old days you could use a 3 conductor cable (no separate ground) with all 3 conductors insulated, but I think that technique is now frowned upon.

I don't own a small MIG welder so I can't comment on this issue ... you need to get advice from someone on this board that has such a machine or check one out at a dealer. The issue isn't really the 40 amp capacity which is OK, but whether the cable you have has adequate number of conductors.

 

[BBQ&Love]

22rifle ... I just took another look at your original post and now note you are proposing to use 8/2 with ground cable (I assume this is a bare ground).

A cable with only 2 conductors and a bare ground will work OK if the welder is a purely 240 volt load, but if the welder you purchase also has any 120v accessories or drives you will need a cable with 3 conductors and a ground. In the old days you could use a 3 conductor cable (no separate ground) with all 3 conductors insulated, but I think that technique is now frowned upon.

I don't own a small MIG welder so I can't comment on this issue ... you need to get advice from someone on this board that has such a machine or check one out at a dealer. The issue isn't really the 40 amp capacity which is OK, but whether the cable you have has adequate number of conductors.

Was thinking about that. My welding experience is pretty limited. Other than a little repair, I have only welded extensively with 3 welders in my life. The stick Lincoln I grew up with. My FIL's MIG (whatever it was; I built a custom 16' trailer with it), and a little 120 volt Lincoln wire feed I used to own. So I don't know if the 120 leg is ever an issue or not.

 

[sberry]

You will be fine with the 8/2wg, its all they need. It will run a 50A stick machine and any current unit that comes with 50A factory cord.

 

[Norcal]

22rifle ... I just took another look at your original post and now note you are proposing to use 8/2 with ground cable (I assume this is a bare ground).

A cable with only 2 conductors and a bare ground will work OK if the welder is a purely 240 volt load, but if the welder you purchase also has any 120v accessories or drives you will need a cable with 3 conductors and a ground. In the old days you could use a 3 conductor cable (no separate ground) with all 3 conductors insulated, but I think that technique is now frowned upon.

I don't own a small MIG welder so I can't comment on this issue ... you need to get advice from someone on this board that has such a machine or check one out at a dealer. The issue isn't really the 40 amp capacity which is OK, but whether the cable you have has adequate number of conductors.

It is not likely that a neutral would be required, if the machine required 120V it would be derived internally in the machine.

 

[BBQ&Love]

Well today I acquired enough 6/3 with ground UF wire to do the run. Well, it's actually 3 times as much as I need.

Cost? 5 minutes and $0.00!

Solved that problem.