HonestDave

I'm getting ready to hook up my Millermatic 175 so I can learn to weld and finally get driving my rocket.
The welder comes factory with a 50 amp plug on it. The booklet says it only draws 20 amps. I don't want to buy all 50 amp plugs and breaker. I also have to make an extension cord from some heavy cable I've got, about 30 feet worth.
Question- Can I cut the end off the welder cord and use all 30 amp plugs and breaker?
I really don't see why not, but thought I'd throw this query out there. Having never welded before....
My thought was - 30 amp double breaker on correct inside 30 amp wire to junction box (about 15 feet) with 30 amp receptacle. Extension cord (30 feet heavy duty) with 30 amp plug and receptacle to go from under house to garage. Next, welder (Millermatic 175 230V) with new 30 amp plug instead of 50 amp.
Any thoughts?

I won't be near a computer after tonight until Sunday, but really would appreciate any input.

oldcutlass

Or you can make an adapter pigtail/box.

Professur

Your owner's manual should have details on swapping the plug. The important thing is to have nothing on the line that's rated lower than the breaker. That way if your welder draws more power than the breaker can handle, the breaker will pop before the wiring or connectors are in any danger.

joe_padavano

I doubt Miller would waste the money on a heavy plug and cord if they didn't feel it was required. Don't confuse average draw with peak.

HonestDave

Point taken.
I think it says peak draw is 19.5 amps, but I'll keep checking. On some forums I've eavesdropped on I've seen people say their 175 came with 50 amp plug, 30 amp plug and some say they came with no plug at all for a while. My dad, being an electrician, has been all over the papers and on the Miller site, and can't find any reason for a 50 amp plug. Same question repeated in other forums. No good reason found. Really trying not to leave any stone unturned here.
Perhaps someone from the ClassicOldsmobile membership has a similar welder and can tell me how they arranged their plugs.

Professur

I run my lincoln sp-170t on 30A .. never had an issue.

citcapp

the owner manual for you machine specifies a 30 amp 230 volt circuit.

30 amp two pole breaker
#10 wire 3 conductor with ground
250 volt receptacle and cord cap (you can use a dryer male plug and female receptacle

HonestDave

Here's a picture of the plug and welder. They've factory installed a 50 amp 2 conductor plus ground plug. Looks like the wire I've got for the panel to the receptacle is rated at 300 volts and is good for a dryer. Think it has three letters with a 30 after them. Maybe means a 30 amp rating. Perhaps it's slowly coming together.

Octania

They probably supply a 50A plug so folks can use their existing dryer/whatnot outlet. And/or that's what was handy for them.

If you draw 20A then any 20/30A setup should do. The only problem with larger connectors is the cost and bulkiness.

Why would you need 3-wire plus ground for a 240V circuit?
There's no need for the Neutral usually on a 240V item.

I admit I have not seen the manual for this particular item. Plus, if you have the N wire handy, you could also put some 110V outlets with the 220V and so when not using the welder you could be using the grinder plugged in there, for example.

Professur

http://www.stayonline.com/reference-...ght-blade.aspx

A useful reference for this conversation.

nicks1966

the reason for the 50 amp plug is cost. Miller used that same power cord on most of the light industrial line and still do to this day. Only one cord to stock.
you don't have to put a 50 breaker in to use that plug, a lot of people I know use it with 30 and 40 amp breakers.


The 20 amps listed first in the owner manual is at the rated output. For the 175 it was 130 amps @ 30% duty cycle. The machine will draw more amps as you increase the output. I have been selling welding equipment for 20 years and still don't understand why the manufactures won't rate the machines at full output.

MDchanic

Breaker rating lower than wiring or plug rating = Safe
Breaker rating higher than wiring or plug rating = Very, Very Bad.

If you want to run a 30A breaker and line and put a 50A plug on it, that's fine - if you ever accidentally connect a 50A appliance, it'll just blow the breaker. This is NOT acceptable according to code, though.

If your dad's an electrician, I say just do whatever he tells you to do.

- Eric

ent72olds

Don't skimp here...have it on it's own breaker, with proper outlet. Buy the right extension cord. Your welder will love you for it. Also, if you are learning the art, you want the confidence that the equipment is working at its peak performance. I once welded in half a floor pan without any shielding gas in the tank...the gague was reading it was half full! Bad gague! I knew it wasn't right when my welds were coming out like bird s#*t! Got a fresh bottle, and felt like I discovered gold! Somewhere in there, there was a moral...

HonestDave

The old guy is suggesting everything be the same and legal. He figures 30 amp all the way if the machine will not draw more than that. He doesn't like the idea of mixing plugs of various amperages. Could confuse somebody. I like to double and triple check with people before I cut the 50 amp plug off the welder. Must be the fear factor.
Also, if I burn the house down, I just know the wife will not be amused.

MDchanic

He's absolutely right - that's why the code is written that way.

Sounds like you're making the right decision.

- Eric

Professur

Personally .. I'd leave the plug on the machine and wire the house for an appropriate 30A 6-30 ... and make a short dongle of 6-30M to 6-50F. Definitely not a long extension with different ends. I'm not a fan of having more connections than necessary .. but in this case ...

mike8162

Check with your electrical inspector. 30A circuits must now use a 4 prong plug. The NEC insists that a neutral wire be used along with the 2 hots and a ground. I think this change was put in place in 2007.

rustyroger

Keep it legal and meeting the codes.
If you don't and the worst happens you may find you have given your insurance company a reason to refuse a claim.

In the UK ALL electrical and gas installations fitted by a tradesman must be signed off by an appropriately qualified person.
You can do it yourself as long as it's done properly, but if you get someone in to do it and they don't get it signed off they are breaking the law.

Roger.

lonestarjarhead

Being a retired electrician myself, I agree with your dad (and I'm running my 175 on 30 amps.) You didn't say, but the 50 amp plug is probably 4 wire type, so 30 amp would need to be also. Reason for having a neutral is that some parts of the Miller probably, like the gas solenoid and the wire spool motor, use 120 V. Good luck. Practice might not make perfect, but ok.

Lady72nRob71

I have seen at various stores, very short 50A to 30A adapting extension cords. Basically they are just plug changing adapters.
I do know I have seen them at harbor freight.
As long as you know a 30A circuit will be adequate for the welder's current draw, the adapting will be fine.

HonestDave

I've got a picture of the plug it came with in box 8. It is a two conductor plus ground 50 amp.

Professur

I don't know any welder that is 4 wire ... as it's internal transformer is more than capable of supplying any voltage needed.

citcapp

Here is the user guide showing the 30 amp circuit for your welder and the required plug and receptacle. The unit requires a three wire circuit 2-hots (230 volts) and a ground. #10/3 conductor cord should work fine


http://www.millerwelds.com/om/o1324k_mil.pdf

HonestDave

Thank you. Looks like enough information to keep me going a while !!