MM210 Wiring Question/Observation

[Gordo]

Hi Guys.

The MM210 was delivered yesterday (Yipee!) in good condition. She's a beauty. When the 18 wheeler pulled up to my house to deliver it, my jaw dropped... but everything worked out OK in the end. Can't wait to start using it!


One observation I thought I'd mention:

I'm getting ready to run the dedicated circuit in the garage. The manual specifies a minimum of 10 AWG for anything less than a 118' run... which makes sense given steady-state max draw of 27A. I'm probably going to run 8 or 10 AWG Copper about 40' on a 30A slow blow breaker and 6-50R plug. Anyway, I thought it was kinda funny that Miller sent the unit to me pre-wired w/ only 12-3 on the cord! (smaller than their own recommendation for the circuit)

I know that for the short length of the pre-attached cord, 12-3 is absolutely fine (12 AWG is NEC rated at 30A anyway). I just thought it was funny that they call out 10 AWG in the manual and then ship it with 12.


Just curious: Do most of you utilize a plug/recepticle circuit for new welders, or do you unwire the pre-attached cable and then hardwire it? Is it common practice to switch over to a twist-lock type, esp for extention cords?

[hankj]

Gordo,

Your use of the term "call out" tells me you've dealt with engineering drawings and specifications at some time in your career!!

It's all good like you are going to do it. For my part, with a welder that weighs as much as the 210, portability is not an issue, so if placement could cause a passer-by to trip on your cord and interrupt your process at a critical time, then I'd twist-loc it.

Otherwise, go for the gusto!! My happines for you is only exceeded by my envy!

Hank

[dyn88]

Im not possitive but I think that solid wire can carry less current than stranded of the same gauge. This is due to the fact that electrons travel over the surface of the wire and the stranded wire has more surface area.

[INTP]

My MM210 shares a 6-50R with my SD180 (not at the same time, of course) which is on 6/3 wire and a 50A breaker. I'm inclined to pull larger wire for the receptacle, so the receptacle can be used for more than just the welder. If you pull 10 AWG wire, it's ok for this application, but not for something else that actually needs the 50A rating.

I also have a 6/3 SO extension cord that they share for mobility around the shop, but as mentioned above, they're both quite heavy so they don't move too much.

I noticed the 12ga cord, too, and also thought it was odd given what you said. It seems to work fine nonetheless.

I'm still getting to know my MM210 but it has impressed me so far. But my previous wire feed was a 135A 120V Craftsman, so it's like going from a Yugo to a Cadillac. Enjoy.

[hankj]

RE: Solid vs. stranded conductors:

Ampacity ratings by the NEC are the same. Genarally, conductors smaller than #6 are solid. #14, 12 & 10 are available as stranded, and are easier to pull in long conduit runs plus easier to work with in boxes that are approaching their wiring capacity. Stranding is done to provide flexibility, so it's said. In any case, even though it's stranded, 750MCM ain't very flexible!!

Hank

[Alex]

If your circuit for the welder is going to be located inside a wall, where you can't feel the wire, I'd err on the side of caution with bigger wire. As INTP mentioned, if you EVER plug in something that requires the full 50A that the recep is capable of, you surely don't want the wire to melt. Ahhh, the horror!

Congrats on the new machine.

Be cool,
Alex

[dyn88]

when I said stranded I ment so cord not bus drop

[Sberry]

The cord on the machine is fine at number 12 for a couple of reasons. One, its temp rating is higher than building wire. It is also short, and the duty cycle of the machine is 60% wide open, most use will never see this machine on top end. The building wire needs to be bigger to reduce V drop for the length of the run and to keep wire temps down.

[Gordo]

I'm inclined to pull larger wire for the receptacle, so the receptacle can be used for more than just the welder.

Yea, I was considering that as well. I'll see what the extra cost would be and make a decision.


The other thing I was considering is that since the welder is going to be used in a 'little' 22' x 22' 2-car garage, instead of running a complicated circuit within the walls to get the recepticle where I would want it (opposite side of the garage from the sub panel), it may be easier/cheaper/smarter to just drop a short 'stub' off the bottom of the sub panel w/ recepticle, and then just always use an extention cord to get me where I need to be. Unless I put 5-6 recepticles around the perimter of the garage, the short 6' cord isn't going to be long enough to accomodate. 5-6 recepticles is going to be prohibitively expensive.

Does anyone make pre-made, flexible, heavy duty extention cables w/ 6-50 connectors on each end? Any recommendations? Is that what the 'SO' acronym reflects?

[hankj]

Dyn88,

I've never heard of solid "SO" covered wire. the "S" means stranded...

Gordo,

Yep, SO is part of the acronym for rubber-covered cord. It's a NEMA specification. Real quick: S = stranded. J = Junior service (300V or less). If there's no "J" in the spec, than it's "Hard Service (600V)". T = thermoplastic. O = oil resistant. W = weather resistant. V = Vacuum cleaner cord.

A complete spec might be "SJT", which would mean "stranded, thermoplastic insulated, junior service cord". "SO" = stranded, oil resistant.

Cool, all this code stuff, huh? It'll make ya crazy!

Hank

[INTP]

Does anyone make pre-made, flexible, heavy duty extention cables w/ 6-50 connectors on each end? Any recommendations? Is that what the 'SO' acronym reflects?

Yes, here is one example.

http://store.cyberweld.com/230voexco25.html

I made mine because it was cheaper to do so.

[Sparky832]

30 amp wire

Hey Gordo
You said that your machine can draw up to 27 amps and that sounds like 30 amp wire would do but NEC states that when designing a circuit , only 80 percent of the circuit should be used or calculated.30ampsX80 percent is only 24 amps. Your circuit should be at least 40 amp and that includes the wire.
Your idea of a receptacle at the panel is a good one, just make up a cord long enough with at least #8 wire, #6 even better.
Good luck with the new machine; Mike

[Sparky832]

30 amp

Gordo
Just another thought,You could remove the factory cord and install your longer cord right on the machine. This would eliminate extra male/female cord ends.(less bulky)

Mike

[Sberry]

Hey Sparky show me where it says this type of circuit says it needs to be 80%. Use a number 10 for a cord if you are making an extension or most of them pre-made come as number 8's because they are designed for use with machines up to the 251 class and for the SD180's. Actually this machine needs an input wire capable of supplying 21.06 A continious. Thats to run it almost wide open at the top of its duty cycle. Since its over 20A they move up to the next size and the building wire doesnt have the temp rating as the number 12 cord that is on it does. In the real world in a small garage it would run on a 12 just fine but the manafacture calls for a 10, so a 10 or larger it must be.