Help getting welder wired in!

[fishpick]

OK - it's time - need the welder... I need to fix the snow thrower I bought... and now - the broken bush hog too! Time to bite the bullet... but before I can post cool welded project pics - I need to get the welder running...

But here's the thing - the manual online for the welder I'm getting says: (http://www.hobartwelders.com/om/0900/o950b_hob.pdf - section 4.6)

Input Amperes At Rated Output - 47.5
Max Recommended Standard Fuse Rating In Amperes - 50
Min Input Conductor Size In AWG - 12

Uhh - am I missing something here? AWG 12 is rated to 20A... Houston Wire & Cable Company - NEC Table 310.16

 

[kennyd]

It has to do with the duty cycle for the welder. Welder outlets are often de-rated this way.

If you can afford it, you may just want to run a #8 and a 60 amp breaker, that way you will be set for just about any welder.

 

[Defective]

Here it goes again...

Yes...

AWG 12 is 20A wire.

Something somewhere says it's ok to run a welder on lighter than normal wire because it's not a continuous load.

I wouldn't use 12 if I were wiring it. The last welder circuit I wired was done with AWG 6 for a 50 foot run to plug in an old Thunderbolt 225. (About the same current requirements, I believe...)

Now watch the debate begin...

 

[Inspector507]

Welders is a case where conductors can be protected at up to 200% of their rated ampacity according to the NECｮ. #12 THHN/THWN is actually rated at 25A. 25A at 200% is 50A. It all depends on the duty cycle rating and and the setting on the welder output
My welder recommended #10 and I went with that.

 

[LarryD]

fishpick, I had the same concerns when I helped a friend wire up his welder. The manual said to use a 100A breaker with #6 wire. I thought it was a mistake but after an electrical engineer told me welders are a classic example of where wire sizes can be derated, we wired it as per instructions and 2 years later it's welding just fine. There are no indications of excessive heat on the wire ends.

 

[hitekcountry]

A lot of people think they're saving money by using the smallest wire allowed simply because thinner wire is cheaper than thicker wire. If that was all there was to it then that would be true. But what many people don't consider is the fact that the thinner wire transmits a lower percentage of what you're paying for (electricity) to the point where it is being used and a higher percentage of electricity (money) is being wasted as heat.

I do just the opposite I almost always wire with the next size larger wire. Example for lighting circuits I use 12awg and outlets I use 10awg.

Pay more now one time or pay more on every electric bill forever.

 

[Highbeam]

It sounds like you are making the run from the panel to the wall mounted female plug for the welder to plug into. Is there any chance that this plug might be used for something else in the future like an air compressor or maybe plasma cutter that won't be able to use this fancy 200% reduction rule? In both of the houses that I've wired in these high amp circuits I used wire rated for the current that the breaker could pass. In other words, no 200% deduction reduction malarchy. I generally like to meet the requirements for electrical work but in this case I will exceed them since there is nothing to say that some holigan down the road won't use my welder plug for his cool new 220 volt electrical space heater.

 

[sandman2234]

Maybe I am out of the loop on this, and out of line, since I am not an electrician, but no way am I going to set up a 50amp breaker on a circuit and run 12 guage wire to the wall outlet. I won't even run 10ga cu wire on that type of circuit. It may seem like cost savings but I really like my house/garage and don't want to risk a fire, especially one in the walls where electricity usually runs.
David from jax

Is the cost savings worth the risk?

 

[hitekcountry]

FWIW I just checked and the outlet for my welder is wired with #4awg. Like I said I tend to go one wire size over what is normally required.

 

[gemini5362]

Welders is a case where conductors can be protected at up to 200% of their rated ampacity according to the NECｮ. #12 THHN/THWN is actually rated at 25A. 25A at 200% is 50A. It all depends on the duty cycle rating and and the setting on the welder output
My welder recommended #10 and I went with that.

I know that you are a professional electrician but I am suprised that you agreed with this. Forget about the welder itself what if you have something shorted maybe something as simple as a mouse chewing the wire or something shorting in the welder. My impression of 12 gauge wire is that it could flame on before it tripped that 50 amp breaker. I would never ever ever consider running a wire with less ampacity than the breaker that feeds it.

 

[Inspector507]

I know that you are a professional electrician but I am suprised that you agreed with this. Forget about the welder itself what if you have something shorted maybe something as simple as a mouse chewing the wire or something shorting in the welder. My impression of 12 gauge wire is that it could flame on before it tripped that 50 amp breaker. I would never ever ever consider running a wire with less ampacity than the breaker that feeds it.

There's a big difference between an overload on a breaker and a fault to ground or a line to line fault. Most likely that 50A breaker is rated to work somewhere between 10,000 and 22,000 amps short-circuit current. Now that'll cook your hotdogs for ya

It's not that I merely agree with it, the engineers at Hobart, the engineers at UL who tested it and the code making panels of the NEC are a heck of a lot smarter than I am.
You can always go better than recommended. And if that's what you want to do, go for it. Poor old fishpick was just asking if he was missing something and I answered his question based upon what the real experts determined was safe.

 

[hitekcountry]

There's a big difference between an overload on a breaker and a fault to ground or a line to line fault.

I don't understand that statement, an over current condition is an over current condition no mater what the cause. And any wire is limited by it's cross sectional area as to the amount of current it can carry. The purpose of a breaker/fuse is to limit the current for a specific wire size, It's the amount of current that maters, what causes the current is irrelevant. So if you're going to use 12 gauge wire then use a 20 amp breaker or at most 25 but not a 50 amp.

Most likely that 50A breaker is rated to work somewhere between 10,000 and 22,000 amps short-circuit current. Now that'll cook your hotdogs for ya

10,000 to 22,000 Amps!! .. No way!! I think you meant to say watts.

 

[Inspector507]

I don't understand that statement, an over current condition is an over current condition no mater what the cause. And any wire is limited by it's cross sectional area as to the amount of current it can carry. The purpose of a breaker/fuse is to limit the current for a specific wire size, It's the amount of current that maters, what causes the current is irrelevant. So if you're going to use 12 gauge wire then use a 20 amp breaker or at most 25 but not a 50 amp.



10,000 to 22,000 Amps!! .. No way!! I think you meant to say watts.

Yes the purpose of a breaker/fuse is to limit the current/load it can carry for a definate time period. It also has a limit as to the fault current rated in AIC or Amps Interrupting Current. It is the amount of current allowed during a fault to ground or fault line to line. And yes I meant Amps not watts.

 

[hitekcountry]

And yes I meant Amps not watts.

So a 50 amp breaker is designed to trip at between 10,000 and 22,000 amps???

 

[SnowRidge]

So a 50 amp breaker is designed to trip at between 10,000 and 22,000 amps???

I believe he means it will briefly handle that much current without damage, while it opens up. It will trip at a nominal 50 amps. It will take longer to trip with a slight overload than it will with a large overload.

 

[Inspector507]

So a 50 amp breaker is designed to trip at between 10,000 and 22,000 amps???

Yes 10,000-22,000 AIC or Amps Interrupting Current, or short circuit current, same thing. They could be rated higher than that. I've seen them over 65,000 AIC.
It's not even related to overload amps. 50A overload is 50A.
What I was responding to is a hypothetical mouse chewing into a wire or a welder shorting out causing a fault not an overload.

There's a big difference between an overload on a breaker and a fault

 

[hitekcountry]

I believe he means it will briefly handle that much current without damage, while it opens up. It will trip at a nominal 50 amps. It will take longer to trip with a slight overload than it will with a large overload.

What it can handle without damage and what current it will trip at are two totally different things.

 

[hitekcountry]

So to answer Gemini5362's example a mouse chews through the wire and you have a wire to wire short, you're saying it ok to have a 12gauge wire protected with a 50A breaker?

 

[SnowRidge]

What it can handle without damage and what current it will trip at are two totally different things.

Which is exactly what I said.

 

[hitekcountry]

Which is exactly what I said.

Yes I know.

What I was Commenting on was the statement by the inspector that

"That 50a breaker is rated to work somewhere between 10,000 and 22,000amps short-circuit current"

That sounds like it is designed to trip at the level more than that it is able to survive at the level.