any welders/ electricians?

[mrspooky]

OK, in one of my threads I ask about an extension cord for a welder and the thread kinda went all over the place so I think I just start here.

  I have a miller XMT 304 CC/CV 230/460V welder. I will be running it in single phase.  It says on single phase it will pull 47.4 / 24.5 amps.   I want to make a 50' extension cord for it. I had a electrician put in a dedicated 2 pole 60 breaker for this welder..  Im thinking that I need a 6/3 cord, but Iv also read that with the duty cycle and the fact that Ill probably never max out the amps that it would be possible to run a 8/3 cord. Any thoughts?

 Thanks

 spooky

 

[smoking b]

If it were me, I would go with the 6/3 - I'm not sure you can even use a # 8 with a 60 A breaker by local code? Anyway with a # 6 you will have less power loss due to the resistive heating power dissipated by the cable. At the risk of boring you senseless I will go through the math.

A standard # 6 wire has a resistance of .395 ohms per 1000 ft, and a # 8 wire has a resistance of .63 ohms per 1000 ft. A 50 ft cable has a resistance of .02 ohms for # 6 and .0315 ohms for # 8. But you have to account for the fact that the return wire also has the same resistance since it has to travel 50 ft to the junction box so that makes it .04 for # 6 and .063 for # 8

For simplicity's sake I'll say that you're running at 2/3 rated capacity which would be 40 Amps. The voltage drop will be the 40 amp current times the resistance - 1.6 volts for # 6 & 2.5 volts for # 8 not a major drop in either case but where it adds up is in the resistive heating power dissipated by the cable. At 40 amps I squared R = 64 Watts for # 6 and 101 Watts for # 8 - over time that extra loss plus random vampire losses would pay for the cost difference of the thicker copper. I'm also a firm believer in going a little overkill so you always have peace of mind.

Anyway... hope that makes sense & it's just my opinion...

 

[mrspooky]

Thanks for the reply!  I had to read it about 5 times,,, but I think it sunk in!! 

 spooky

 

[smoking b]

 
Thanks for the reply!  I had to read it about 5 times,,, but I think it sunk in!! 

 spooky

You're quite welcome man 

 

[bigboysmokehous]

I concur on the 6/3soow cord. I recommend trying to find a premade cord compared to buying the components and building it. Depending where your at I can see if a sister company is around there to help you out. I am a electrical equipment salesman in Wisconsin.

 

[smoking b]

If you don't want a premade cord or can't find one it's quite easy to put a plug on 

 

[mrspooky]

If you don't want a premade cord or can't find one it's quite easy to put a plug on 

Yea, I think thats the route im going to take. I got a price on 6/3 cord and its $3.05 a foot. Another place just down the road from there wanted 4 and some change a ft.
thanks
spooky

 

[smoking b]

Yea, I think thats the route im going to take. I got a price on 6/3 cord and its $3.05 a foot. Another place just down the road from there wanted 4 and some change a ft.
thanks
spooky

Good deal - sounds like you'll be up & running shortly then 

 

[cparktd]

Have you considered extending the welder leads themselves. Not sure how the cost would compare. You can likely buy them pre made or they sell the lead cable by the foot at most welder supply shops.

 

[mrspooky]

Yup. Im gonnna go 50' on those too. Im trying to do this right the first time.