Another electrical question - MEP8XX running welder

[jimbo913]

Picked up a barely used Hobart 235LX AC/DC stick welder and plan to power it with the MEP803.
The welder data plate states 230V 48A and based on an online wire sizing calculator, I would need 6AWG for a 5-10' extension cord. However, the welder is only using 12/3 for its 3' power cord. I have some 12/3 and 10/3 cable to make a 5-10' extension cord from the MEP, so what should I do?

The welders duty-cycle is 100% at 100A AC and 100% at 60A DC but at max output it is only rated at 20% duty-cycle. Maybe thats why it only has a 12/3 power cord?

 

[Triple Jim]

I ran a Miller Econotig with similar current requirements with a 50 foot extension cord I made from #8 type SO cable. #12 sounds a bit small though. I wonder in someone changed the cord at some time in the past. You could try the #10 cable for the extension and see if it gets too warm in use. #10 Romex is good for 30A when it's in walls, according to the code, so I'd expect it to work OK.

 

[jimbo913]

Based on the grommet where the cord comes out I am willing to bet it is factory 12/3 with original cable. I will call the factory tomorrow and verify that they use 12/3. If they do, I think stepping up to 10/3 for 10' extension should be fine.

 

[Keith_J]

The 48 amp draw is only for a brief period. At 225 amp output and ~30 volt arc, that is 6750 watts, at 240 volts that is 28 amps.

my Miller Dynasty 200 DX also has a 12 gauge power cord but that is 3 phase. The manual specifically states the power cord limits output in single phase especially in 120 volt mode. It has no issue in 208/240 three phase.

 

[Triple Jim]

Your Dynasty is an inverter welder, but I don't think the Hobart is. Transformer welders are pretty inefficient. I know my Econotig used to use every bit of its 50A 240V input rating when I ran it at full output, although as you said, the duty cycle is low in that case.

 

[jimbo913]

The factory verified the wire to be 12 guage and stated that it is safe based on a 20% duty cycle. They did confirm that 20% is controlled by the operator only (no thermal switches), which seems unsafe to me. I will use the 10/3 to go 10' from the generator and limit usage to 20%.

Next question: when running the generator I will not bond neutral to ground on the MEP since the welder is only 3 wire but I was planning to run the generator ground to earth.
However, that is a major pita since the welding location changes. How the heck do the guys that run mobile welding trucks ground everything? Or do they just take a risk??

 

[mmthomas]

HI - I'm a long time lurker and first time poster, and very thankful for all the great info available and the generosity of the posters.

I recently bought a MEP803A and brought it back to life..thought rather easy as it just requires some reassembly. Still need the overflow tank hookup and redo the battery charging circuit (new fuse holder).

So, with this purchase, and in addition to supplying the week or two needs of the house when power is out, I plan to run a miller XMT 304 0r 350 in 3 phase mode and replace my mig welder with a suitcase and go off welding gates and such. Likely push it now and then to the limit with some thick stuff, but mostly just 1/4".

Any recommendations or concerns?

Thanks all!

 

[jimbo913]

Welcome to the forum.

I recently bought an ESAB 350mpi I plan to run 3-phase on the 803. Just pay attention to proper grounding. I wont get into it and start a new thread on an old subject, so just do a search.

 

[mmthomas]

Thanks Jimbo913!

Found lots on connecting ground for home power, but not remote power (for welder as example). Will keep looking.

My water heater load bank worked well and can boil water fast too!

 

[jimbo913]

For remotely running a welder it is best to drive a ground, which sucks of course. Search for welder and that keyword may help. I use my mobile device to access this site, so its a pain or I would find the link and post it.

 

[mmthomas]

Thanks!!

So I just wrapped up the fluids and filter change, and used my water heater load bank and all good. Running 2 wire 240 on the elements.

For welding, I need some help. N and G appear connected and both ground to frame... I am NOT an electrician, and have had a few good zaps in life, so not wanting to damage the unit or my unit, and use the three wire setup 220V on the welder, what do I connect L1, L3 and N and or G, or do I remove the bar that connects G to N?

 

[mmthomas]

BTW, I've searched and read quite a few posts, but unfortunately, get a bit confused on terminology and need more exacting directions. Perhaps have not found the right set of posts....

Thanks All!

 

[CT-Mike]

Thanks!!

So I just wrapped up the fluids and filter change, and used my water heater load bank and all good. Running 2 wire 240 on the elements.

For welding, I need some help. N and G appear connected and both ground to frame... I am NOT an electrician, and have had a few good zaps in life, so not wanting to damage the unit or my unit, and use the three wire setup 220V on the welder, what do I connect L1, L3 and N and or G, or do I remove the bar that connects G to N?

I am no electrician so take this advice with a grain of salt. When you're generator is not connected to your house and running in stand alone mode ( i.e.: running your welder in the back 40), you need to drive a ground rod. Ground and neutral need to be bonded together at the generator output terminals.

 

[Korgoth1]

Red and black are your hots, neutral and ground are the same in this situation.

 

[DieselAddict]

I am no electrician so take this advice with a grain of salt. When you're generator is not connected to your house and running in stand alone mode ( i.e.: running your welder in the back 40), you need to drive a ground rod. Ground and neutral need to be bonded together at the generator output terminals.

To be code compliant you are correct that the ground and neutral need to be bonded. Surprisingly it is not REQUIRED to drive a ground rod BUT I highly recommend it.

 

[mmthomas]

Mep803a up and running. Tested with 13.5kw of heaters for 15 minutes and rock solid!!

 

[mmthomas]

Thanks everyone.

Wife claimed the above unit for house backup power...now I have to buy another for the trailer/welder/port power...!!!

Lets hope the next one arrives in as good condition.