Wire and conduit size question

[signcrafter]

Need to run an outlet for my welder. Welder plate says 47.4 amps at 230 volts. At my last house I just ran some 6/2 with ground from the panel to an outlet a couple feet away. This house I will need to run conduit with some thhn in it do to locations. Run will be roughly 30 ft from the panel. Right now the welder has a nema 6-50 plug on it.

I'm guessing I need to use 6 gauge thhn in the conduit? Do I need three 6 gauge wires or can I run 2 6 gauge and a smaller one for the ground? Or do I even need a ground with the conduit?

Second, what size conduit do I need? I have a bunch of 3/4" stuff but not sure that will be big enough? If I'm reading the chart right I can run 4 number 6 wires in 3/4" conduit so I should be good but just don't want it to be too tight.

Thanks

 

[ddawg16]

As long as you are sure you don't need a neutral, 2 ea #6 THHN (or THWN if the conduit goes under ground) along with a #10 ground will work....and fit in that 3/4" conduit.

If it was me, I'd also run a white #6 neutral just in case.

As long as you don't have more than 1-2 bends, it's not a bad pull. You can make it easier if you use a bare #10 for the ground.

If you upsize the conduit to 1", it's a lot easier.

I personally don't like depending on conduit as the ground....but that is just me.

 

[sberry]

What model welder is this? If you are piping it there are a lot of options. Number 8 in pipe is a full welder circuit for the biggest machines that come cord and plug. If this is a buzz box type the legal limit is 12/50 and they come 12 cord. Using number 10 reduces any line loss. I got some number 6, I had free wire. If I have to buy it then it's a different matter as well as the length.

 

[sberry]

Use conduit you have. If you have to buy wire you can use 2 black 10 and green ground, you can use the pipe too. In a wood structure I run ground if I have it, on iron building I don't always do it. Some of the 250 class feeders do require 8, some allow 10. A 252 Miller calls for 8 but,,, it will really cook and put above it's rated output with big wire, special gas and a different gun than comes on it,,, not even a factor for home/hobby where it's typical for 1 wire 1 gas, mostly c25. My extension cords are 10, I have a 255, as hard as I run it can't warm the wire. As a side note (or additions to owners manuals) these numbers are single circuit in pipe.

 

[signcrafter]

Model is miller 304.

I was just doing some reading on miller's site and here is a link to the manual, https://www.millerwelds.com/files/owners-manuals/O2208AP_MIL.pdf.

It says I can use #8 wire with a max breaker of 60 with a max run of 85'. I'm well within that length. So should I just go with #8 then?

Does this need a disconnect at the plug? I think the plug would be the disconnect right? But would there be any advantage to putting a disconnect right before the plug, they are cheap enough and might be nice to have a "switch" to shut off power to welder when not using it?

 

[sberry]

The welder has a switch, it's double pole. At 1/2 the allowable length the 8 is dandy.

 

[signcrafter]

The welder has a switch, it's double pole. At 1/2 the allowable length the 8 is dandy.

Ok thanks.

 

[sberry]

I looked, a couple notes,,, some of this regards earlier posting so,,, if you notice it also requires an 8 ground wire,,, it's is due to the fact that there is a possibility of fuses at 80A. Could be due to common use of bigger wire and even if wired in industrial to a shared circuit with larger breakers,,, it's ok to understand why but the fact is it calls for it.
Second ,,,, in regards to some earlier stuff i wrote about allowable for uits, some applies, some doesn't due to the machine does not come factory plug because it is dual voltage and dual phase. There were no factory adapters at that time, the installer was to put plug on, even hard wire it so it calls for a specific intetional dedicated circuit, only reason it can be plugged in is someone added plug.
This thing really has some poop, 60% at rated and will output close to 400 under some circumstances.

 

[sberry]

This might be found in ship building or similar, on assembly line for mobile home frames, will run some feeders and the largest practical manual rods. Some limited use with air carbon arc.
The reason I pick on this type f thread is that its not understood very well. If a guy looks at specs a buzzer is rated the same amp in, 47.5 and allows 12 wire. On these small machines I do not follow the legal limit but run a size up, for a couple reasons. The outlets and plugs may be listed 10 and up, 10 makes so much better terminations and with the min wire they suffer some substantial voltage drop.
Its been a while since I test and read the charts but,,,, and,,,, while they7 are rated, its rare a buzzer really sees 48 in but closer to 40 so there is some juice built in but its a lot of drop unless the circuit is really short (they allow 85 ft), not so bad if its short but still some and back to the same connections. With 10 wire drops to 3v loss vs 15, doesn't effect the machine adjustments and tolerates exceeding duty cycle.
The compact wire feeds are 14, again, wide open a fair amount of loss on longer circuits and need special connections at terminations.

When we get to the larger machines the wire is sized up some for duty cycle, the 304 can draw the same 2x as long, maybe more, even at same output. It would run from a 12,,, just not as long or hard, its not really for performance but for wire heating and in this case allowing it on higher breaker or fuses than the 50 to a buzzer.

 

[signcrafter]

Ya it's way more machine I could ever use but I got a great deal on it and then found an S-64 wire feeder for it. Has been a good machine.

So just to clear up the electrical, 3 #8 wires is what I need right? Would there be any reason to go with #6 wires over the #8s? The run isn't long so cost wouldn't matter too much. But if there isn't a need because I won't be pushing this machine hard at all I will just go with #8s for now.

3/4" conduit is still good for 3 #8s right?

The plug, are you saying the plug isn't supposed to be there? Is it alright to have on there? I don't really want to hardwire the unit to the wall if possible.

 

[sberry]

The conduit is great for 3/8's There is no real technical reason to use wire larger than that especially since you are at 1/2 the distance. The plug is fine there except for 1 thing, its on a 60 vs a 50 which means its really only for this welder and not for smaller machines that are limited to 50. From an electrical perspective its on, from a code issue somewhat iffy but if it isn't there you might then require a disconnect if the breaker isn't local or in sight.

What I do may be different, same for others here as I can do it at cost and its such a reaction not significantly more work for me. I might be tempted to use a 6 space panel, they are cheap, run a 6 wire, wire this machine to a 60 breaker, use another space for a common outlet for tools if there was a chance I needed it, would allow the addition of another 240 for a smaller welder and serve as disconnect means for this machine. I might go 2/6 and 2/8 to make it a bit easier in the 3/4 pipe I had. Pipe first, then measure wire.

 

[sberry]

One more thought,,, you can use the 8 and a 50A breaker and it would be legal for anything that come factory cord and plug. This machine can really burn,,, you will never trip a 50 and would make the circuit completely code compliant.

We hear endless **** about wiring up for larger welders, this is a case for making it legal for smaller ones too. Reason for the 60 on this machine is for use above its rated output.

 

[signcrafter]

One more thought,,, you can use the 8 and a 50A breaker and it would be legal for anything that come factory cord and plug. This machine can really burn,,, you will never trip a 50 and would make the circuit completely code compliant.

We hear endless **** about wiring up for larger welders, this is a case for making it legal for smaller ones too.

I have a 50 amp breaker I was planning on using already so should be good to go.

Sub panel is an interesting idea. I do need to add a couple circuits in the garage for an air compressor and some outlets. But don't think I really want a sub panel anywhere between where the main panel is now and where the welder outlet is going to go. So I would need a longer run of number 6 to put the subpanel where I would want it and end up costing more then just running those other 20 amp circuits out of the main panel. Main panel is pretty accessible from the garage, not within eye sight but one door and maybe 15 feet so not inconvenient if I need to get to it. Just don't have a good space on the wall in the garage to put the sub panel and wiring for it at this time until everything is in place. But thanks for the idea, I will keep that in mind for down the road.

 

[sberry]

Just use the 8/50 and a plug for disconnect means especially since you already have a breaker. That is a super good solution, nothing really beats a single circuit in pipe for this kind of thing and eliminates any future confusion. Run another pipe for new equipment if and when needed especially if you have spaces in the main.
An air comp would be subject to the same disconnect requirements. By letter of the law it is sposed to be in view if the source breaker is used for disc. (I see you mention 20A for air comp), the plug would qualify.
They simply want it in sight to prevent someone you cant see from walking up to it and turning it on while its being worked on.

 

[signcrafter]

Just use the 8/50 and a plug for disconnect means especially since you already have a breaker. That is a super good solution, nothing really beats a single circuit in pipe for this kind of thing and eliminates any future confusion. Run another pipe for new equipment if and when needed especially if you have spaces in the main.
An air comp would be subject to the same disconnect requirements. By letter of the law it is sposed to be in view if the source breaker is used for disc. (I see you mention 20A for air comp), the plug would qualify.
They simply want it in sight to prevent someone you cant see from walking up to it and turning it on while its being worked on.

Right. For the compressor I'm probably going to get a disconnect and hardwire it since it doesn't move and it is nice to have a switch for it right by it. Had a thread on that last month to figure out what disconnect to use. https://www.menards.com/main/electr...3801-c-6435.htm?tid=-3795415639211031&ipos=48

 

[pattenp]

This is a cheaper disconnect for the compressor.... https://www.menards.com/main/electr...85-c-6435.htm?tid=4351960689448472678&ipos=30

 

[wyliesdiesels]

As long as you are sure you don't need a neutral, 2 ea #6 THHN (or THWN if the conduit goes under ground) along with a #10 ground will work....and fit in that 3/4" conduit.

If it was me, I'd also run a white #6 neutral just in case.

As long as you don't have more than 1-2 bends, it's not a bad pull. You can make it easier if you use a bare #10 for the ground.

If you upsize the conduit to 1", it's a lot easier.

I personally don't like depending on conduit as the ground....but that is just me.

Dont need #6 THHN as #8 is rated for 50a.

Ya it's way more machine I could ever use but I got a great deal on it and then found an S-64 wire feeder for it. Has been a good machine.

So just to clear up the electrical, 3 #8 wires is what I need right? Would there be any reason to go with #6 wires over the #8s? The run isn't long so cost wouldn't matter too much. But if there isn't a need because I won't be pushing this machine hard at all I will just go with #8s for now.

3/4" conduit is still good for 3 #8s right?

The plug, are you saying the plug isn't supposed to be there? Is it alright to have on there? I don't really want to hardwire the unit to the wall if possible.

You need 2 #8s and 1 #10. If you use metal conduit, you could skip the #10 for the ground wire but make sure to bond the outlet to the box.

I have a 50 amp breaker I was planning on using already so should be good to go.

Sub panel is an interesting idea. I do need to add a couple circuits in the garage for an air compressor and some outlets. But don't think I really want a sub panel anywhere between where the main panel is now and where the welder outlet is going to go. So I would need a longer run of number 6 to put the subpanel where I would want it and end up costing more then just running those other 20 amp circuits out of the main panel. Main panel is pretty accessible from the garage, not within eye sight but one door and maybe 15 feet so not inconvenient if I need to get to it. Just don't have a good space on the wall in the garage to put the sub panel and wiring for it at this time until everything is in place. But thanks for the idea, I will keep that in mind for down the road.

Whats the HP rating on the comp?

 

[signcrafter]

You need 2 #8s and 1 #10. If you use metal conduit, you could skip the #10 for the ground wire but make sure to bond the outlet to the box.

According to the manual I linked above Miller says minimum of number 8 for the ground.

Whats the HP rating on the comp?

3 hp.

 

[sberry]

It is 8 ground in this case. I could about buy the idea of a 10 for it with 50A,,,, the lesser machines allow it I believe unless a 252 wants 8, don't recall. I believe its 10 but is limited to 60A fuses where the 304 is 80

Dont need #6 THHN as #8 is rated for 50a.

And its listed for it.

 

[wyliesdiesels]

According to the manual I linked above Miller says minimum of number 8 for the ground.

not sure why they list #8 when NEC permits #10 upto 60a.

The manu. is going overkill

https://www.safecoelectric.com/images/resources_pdf/NEC2008 Table 250.122.pdf

 

[sberry]

No,, why,, it allows for fuses to 80A. Maybe even higher if it was connected to shared circuit in industrial?
The compact wire feeds, 240v models list 14 wires for hot but 12 for ground.

 

[wyliesdiesels]

No,, why,, it allows for fuses to 80A. Maybe even higher if it was connected to shared circuit in industrial?
The compact wire feeds, 240v models list 14 wires for hot but 12 for ground.

i see now. its cause of the recommended fuse size for normal fuses(non time delay)

A comparable breaker may have the same time delay characteristics of a 60a TD fuse and i suspect #10 would suffice for the EGC.

 

[sberry]

Would think so and wouldn't be of concern if it was on a 50A circuit. Not something to lose any sleep over. I would be simply plugging it in to one of my welder outlets that are 6 wired.