50 amps over 10AWG?

[CoopVA]

So this morning I fired him. He had no plans to put in grounding rods and was planning to run ground from the main panel. (Which was of course, some lie or backtracking because he told me explicitly only 3 cables in the ground earlier.) He said that he, 'spoke to his buddies' and they all said that 50 amps over 10 gauge would be fine. I know for a fact that if you're going to split it between multiple circuits you for sure need 6, maybe 4 AWG (though maybe if its for a dedicated welder or A/C unit maybe you don't - debatable based on this thread haha).

Looks like I'm going to have a go at it myself. Unfortunely he already trenched and put in a 1/2'' conduit line and buried it WITHOUT a pullstring,

Wow!


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[acmikee]

what type of conduit did he run underground. its not emt is it?
hopefully its pvc or ridgit

 

[91bronc300]

It is not so much surge currents, but duty cycle. If your dedicated welder outlet is only ever going to have a welder with a 35% duty cycle plugged into it, that means that the circuit will only be drawing a high level of current 35% of the time, because the welder itself can't handle any more than that. The rest of the time the wire will have very little current flowing through it. That resting period gives the wire time to dissipate any heat generated and stay cool even though it is smaller than normal. It has been a few years since I did commercial electrical, but you also used to be able to use smaller wires for things like commercial laundromats, because the dryers were rarely running continuously for a long period of time.

That makes sense. Pretty much what sberry said. Thanks.

 

[2ManyProjects]

So this morning I fired him.

Good move, for all sorts of reasons.

Is that because welders do not have the the high starting current like motors do?

No. It's based on the concept of "duty cycle"; "jeremy v" explained it perfectly.

That said, just because you CAN "get away with" undersized wiring on a dedicated welder circuit, that doesn't mean it is necessarily a good idea to do so. The welder you're running off that undersize wiring will still be subject to such things as the voltage drop imposed over the length of run (which will be more severe at shorter distances, the lighter the wiring is), and therefore perhaps not perform to it's peak potential (tho' whether you'd notice the difference in any particular scenario is at least debatable, and will depend on the specific details of that scenario). And besides, someday you may want to use that circuit for something other than a stick welder -- ooops!

I ask because just the other day I made a 50 foot 240 extension cord out of 10/3 and 50 amp plugs. I had been using some 8/4 for an extension cord (I know, 1 wasted conductor) but wanted to use it for something else and I had the 50 foot piece of 10/3 laying around. So I looked up online the ampacity for 10 gauge and it said 55 amps so I figured that's more than the 50 amp plugs so I took the plugs off the 8/4 and put them on the 10/3.

NO WAY that 10/3 is good for 50+ amps.

Extension cords are not subject to the same "rules" as permanently installed wiring; but that doesn't mean that common sense should be thrown out the window. Per the NEC, AWG 10 wiring is good for 30-40 Amps, depending on the specific type of wiring and the temperature rating of its insulation. Normally, the lower limit applies.

Extension cords are generally limited to lower maximum currents than permanently installed wiring, in part because they are routinely subjected to wear, tear and general abuse, and thus must be presumed to be somewhat degraded in the field.

Compare your "home brew" cord to:

http://www.homedepot.com/p/Tasco-50...d-Yellow-with-Black-Stripe-05-00118/203534037

and note: "Maximum Amperage (amps) 15 A"

Now, I might reasonably push things a LITTLE further than that (perhaps 20-30A), if I had the need; but certainly not to anything like 50 Amps.

Also, the very fact that it is an extension cord means the effective length of the wiring run is being extended, and thus voltage drop becomes more of an issue. Running 50 Amps through a 50 foot AWG 10 extension cord will impose about 6.2V of drop just in the extension cord itself, before any of the wiring leading up to the receptacle that cord is plugged into is even considered. At 240V, that's "edgy" at best; at 120V, it is grossly excessive.

So I guess that means the 10/3 can only be used to the full 50 amp rating of the plugs if I use it with a welder?

Well... Not exactly. But for practical purposes, that's probably not a horrible way to think about it. I'd still be nervous about 50A, tho', even for that application.

This chart right here: http://www.powerstream.com/Wire_Size.htm it says you can use 10 gauge for 55 amps if it's 'chassis wiring', whatever that is, but only 15 amps for power transmission.

YUCK!

That page is an absolute travesty of misinformation, "voodoo engineering", and inappropriate sweeping generalizations. You should ignore it entirely. By the author's own admission, the information on load carrying capacities is third-hand; and he even goes on to further waffle with statements like "the rated ampacities are just a rule of thumb." In short, it is simply NOT a credible reference.

And BTW, "chassis wiring" refers to 12VDC automotive wiring -- not exactly what we're dealing with here!

Then you say 10 gauge is only good for 30 amps for a general use cord.

Actually, that would be for permanently installed wiring, which is not subject to the various additional issues which affect extension cords.

Then quoted above it says 10 gauge is good for 50 amps for a dedicated welder circuit only.

As discussed above, that's a special case.

I guess I'll just use it until it melts

Not a good idea. What exactly are you planning to run off this home-brew cord? If it is a relatively light load, fine. But I certainly would NOT recommend you even attempt to draw anything like 50 Amps through it, even in short bursts.

I honestly didn't think any more of it after making the cord until I saw this thread.

We live to serve.

Says SJTW on it. I don't know the manufacturer. The outer jacket I would guess is PVC. The insulation on the actual conductors seems like a nice rubber.

Well, that much is good anyway. "SJTW" stands for:

S = Service Grade
J = Hard Service
T = Thermoplastic
W = Outdoor (sunlight resistant jacket and 
      wet location rated conductors)
.

Or, in something approximating English: That type rating means the cord is generally suitable as an outdoor extension cord.

 

[Castel]

That's stupid...

 

[pattenp]

The reference you pointed to is not for the make up of general power extension cords as regulated by the NEC. The cord you made up for your welder is not suitable for general power transmission because you have 50A plugs on a 30A cord. The cord should be tagged for welder use only to help prevent its use as a 50A general use power cord.

Edit: I see 2many commented on this, so sorry to repeat.

This chart right here: http://www.powerstream.com/Wire_Size.htm it says you can use 10 gauge for 55 amps if it's 'chassis wiring', whatever that is, but only 15 amps for power transmission. Then you say 10 gauge is only good for 30 amps for a general use cord. Then quoted above it says 10 gauge is good for 50 amps for a dedicated welder circuit only.

I guess I'll just use it until it melts

I honestly didn't think any more of it after making the cord until I saw this thread.

 

[sberry]

Agreed, its a welder cord and not for a kiln. My floor is cold, ran a 250 feeder with 035 as steady as I could for 20 minutes and couldn't feel any temp rise in a 10. Even in hot weather would have to really work to get much rise in a 10.

I have run a lot of welding machines on 10 wire. Some of them should be highlighted in the code violation thread.

 

[sparky7]

Its not ideal to run 50 amps on that 10 gauge welder cord and it will probably cause problems if you run the welder wide open for any length of time. Im sure it works fine for what you are doing though, its going to heat up if you push it - so be careful and plan to upgrade to bigger cord if you are going to push it

You know you can buy soow online way way cheaper than in the store. I paid around 600 dollars for 250 feet of 6/3 soow and made a monster cord like no other

 

[katy]

Unfortunely he already trenched and put in a 1/2'' conduit line and buried it WITHOUT a pullstring,

Whats the issue w/no pull string? You did say it was 75'. Never heard of a fish tape? There's a reason they make them 100' long

 

[91bronc300]

Good move, for all sorts of reasons.




No. It's based on the concept of "duty cycle"; "jeremy v" explained it perfectly.

That said, just because you CAN "get away with" undersized wiring on a dedicated welder circuit, that doesn't mean it is necessarily a good idea to do so. The welder you're running off that undersize wiring will still be subject to such things as the voltage drop imposed over the length of run (which will be more severe at shorter distances, the lighter the wiring is), and therefore perhaps not perform to it's peak potential (tho' whether you'd notice the difference in any particular scenario is at least debatable, and will depend on the specific details of that scenario). And besides, someday you may want to use that circuit for something other than a stick welder -- ooops!



NO WAY that 10/3 is good for 50+ amps.

Extension cords are not subject to the same "rules" as permanently installed wiring; but that doesn't mean that common sense should be thrown out the window. Per the NEC, AWG 10 wiring is good for 30-40 Amps, depending on the specific type of wiring and the temperature rating of its insulation. Normally, the lower limit applies.

Extension cords are generally limited to lower maximum currents than permanently installed wiring, in part because they are routinely subjected to wear, tear and general abuse, and thus must be presumed to be somewhat degraded in the field.

Compare your "home brew" cord to:

http://www.homedepot.com/p/Tasco-50...d-Yellow-with-Black-Stripe-05-00118/203534037

and note: "Maximum Amperage (amps) 15 A"

Now, I might reasonably push things a LITTLE further than that (perhaps 20-30A), if I had the need; but certainly not to anything like 50 Amps.

Also, the very fact that it is an extension cord means the effective length of the wiring run is being extended, and thus voltage drop becomes more of an issue. Running 50 Amps through a 50 foot AWG 10 extension cord will impose about 6.2V of drop just in the extension cord itself, before any of the wiring leading up to the receptacle that cord is plugged into is even considered. At 240V, that's "edgy" at best; at 120V, it is grossly excessive.



Well... Not exactly. But for practical purposes, that's probably not a horrible way to think about it. I'd still be nervous about 50A, tho', even for that application.



YUCK!

That page is an absolute travesty of misinformation, "voodoo engineering", and inappropriate sweeping generalizations. You should ignore it entirely. By the author's own admission, the information on load carrying capacities is third-hand; and he even goes on to further waffle with statements like "the rated ampacities are just a rule of thumb." In short, it is simply NOT a credible reference.

And BTW, "chassis wiring" refers to 12VDC automotive wiring -- not exactly what we're dealing with here!



Actually, that would be for permanently installed wiring, which is not subject to the various additional issues which affect extension cords.



As discussed above, that's a special case.



Not a good idea. What exactly are you planning to run off this home-brew cord? If it is a relatively light load, fine. But I certainly would NOT recommend you even attempt to draw anything like 50 Amps through it, even in short bursts.



We live to serve.



Well, that much is good anyway. "SJTW" stands for:

S = Service Grade
J = Hard Service
T = Thermoplastic
W = Outdoor (sunlight resistant jacket and 
      wet location rated conductors)
.

Or, in something approximating English: That type rating means the cord is generally suitable as an outdoor extension cord.

Hot damn, now that's an answer

Well, as far as what I'll use it for. A 2hp 12" bench grinder and a 1.5hp drill press if I ever need to move them away from the wall. But mostly an old 250 amp Forney arc welder, a 50 amp Chinese plasma cutter (that I hate), and a 3 phase Linde MIG welder that I plan to do a Haas Kamp conversion (look it up, pretty cool stuff) on this Spring. I will probably figure out something else for the Linde when the time comes so basically it's just for an old 250 amp buzz box and a 50 amp plasma cutter.

Thanks for the excellent answer BTW.

Agreed, its a welder cord and not for a kiln. My floor is cold, ran a 250 feeder with 035 as steady as I could for 20 minutes and couldn't feel any temp rise in a 10. Even in hot weather would have to really work to get much rise in a 10.

I have run a lot of welding machines on 10 wire. Some of them should be highlighted in the code violation thread.

This is about my way of thinking too. To just try it out and see what happens (I haven't tried it yet), see if it gets warm or not.