Welder circuit size and flexible cord?

[ritelec]

Hooking up a multi tap arc welder for a muffler shop.
At 230v name plate says 55 amps. It came provided with
8-3 ST cord and a 50 amp single phase with ground plug

How do I figure out its duty cycle as per 630.11(A) ?

Judging by the flexible cord rated at 40 amps I'm guessing the manufacturer is rating it at 50 .

At 55 amps shouldn't my circuit be a 60 amp ?
If so then 630.13 where it states the disconnect means shall not be less than that necessary to accommodate over current protection which is 60. The cord plug is 50 amp.

It's temped out right now on an existing 40 amp circuit and its drawing anywhere from 35 to 42 amps for what he doing but he's talking about using it on thicker metals and it should be wired to handle the greater loads, I'm thinking it needs the 60 amp circuit. It's also running temporarily using what was the existing 10-3 so cord that was supplying the existing 35 amp welder that burnt up

I'm planning on running a 60 amp circuit. Installing a 60 amp knife disconnect switch and use #6-3 SO to the new welder.

As the code reads would I have been able to install a 50 amp plug and receptacle with the #8 flexible cord?

Or am I on the right path making everything 60 amp?


Thank you.

 

[zbang]

How do I figure out its duty cycle as per 630.11(A) ?

Don't most welders show that on the plate (or on the spec sheet)? (Picking one at random, the lincoln pro mig 180 has a DT of 30% on the spec sheet.)

 

[Jraef]

It's actually required to be on the welder nameplate.

 

[ritelec]

Thank you.

I checked the welder and duty cycle was not on plate (that I could see) google search showed 40%. I max is 55 A, I eff is 37A at 230v.

Lincoln Electric 260 Power Mig

I will open book later and try to see whats needed again.
circ. conductor size
circ. overcurrent protection
disconnect (plug/recept) amperage rating
flexible cord conductor size

Thanks again

 

[oldsparky52]

Hooking up a multi tap arc welder for a muffler shop.
At 230v name plate says 55 amps. It came provided with
8-3 ST cord and a 50 amp single phase with ground plug

How do I figure out its duty cycle as per 630.11(A) ?

Judging by the flexible cord rated at 40 amps I'm guessing the manufacturer is rating it at 50 .

At 55 amps shouldn't my circuit be a 60 amp ?
If so then 630.13 where it states the disconnect means shall not be less than that necessary to accommodate over current protection which is 60. The cord plug is 50 amp.

It's temped out right now on an existing 40 amp circuit and its drawing anywhere from 35 to 42 amps for what he doing but he's talking about using it on thicker metals and it should be wired to handle the greater loads, I'm thinking it needs the 60 amp circuit. It's also running temporarily using what was the existing 10-3 so cord that was supplying the existing 35 amp welder that burnt up

I'm planning on running a 60 amp circuit. Installing a 60 amp knife disconnect switch and use #6-3 SO to the new welder.

As the code reads would I have been able to install a 50 amp plug and receptacle with the #8 flexible cord?

Or am I on the right path making everything 60 amp?


Thank you.

I haven't read that section in decades, but IIRC, yes and you might actually be allowed to go to a smaller wire. I would have to go reading to be sure.

 

[ritelec]

The existing circuit is #8 thhn in conduit on a 40 amp brk
Looks like 630.11 will allow them for supply conductors. I eff =37 amps
Duty cycle 40 = 55 max amps x .63 = 34.65 amps.
Am I reading this right?

630.12 OC protection up to 200% of welder Imax and 200% of conductor ampacity rating. 55x 200 % = 110 amps.

630.13 disconnect has to be rated for OC protection.

Is that saying that I can put the 8's on a 110amp breaker and the disconnect has to be rated for 110 amps ???

Also 630.13 says disconnecting means shall be a switch or circuit breaker. Does that mean that the supplied plug and receptacle are not allowed as a disconnect?

Can I use the existing 40 amp circuit with 8's for this welder and use the supplied 8-3 so cord rated 40 amps with the 50 amp plug ?

It's mentioning OC to be not over 200 percent of welder current. But it doesn't give you a definite number. Do you just pick a OC size that you feel like picking up to that 200 percent ?

The existing # 10 rubber cord is rated for 30 amps per 400.5. Do I change it to the supplied #8 rubber cord rated 40amps ? Is the rubber cord part of 630.12 OC supply conductors so that the flexible cord should have be 6's rated for 55 amps and not the supplied 8's?

Thank you.

 

[suemarkp]

I think Ieff is what takes duty cycle into consideration. Think of it like the MCA value on an HVAC system. That is what the circuit wires needs to be sized for. The circuit breaker can be larger than this, and is sized no more than 200% of Imax.

With an Ieff of 37A, #8 wire is good.

 

[ritelec]

Thank you. So I can leave it on the existing 40 amp breaker and "if" it starts tripping I can replace the breaker with a 60 or up to 110. Interesting.

What do you think about the welders cord?
8-3 so at 40 amp as was originally supplied or 55 amp 6-3 so cord ?

 

[zbang]

What do you think about the welders cord?
8-3 so at 40 amp as was originally supplied or 55 amp 6-3 so cord ?

If the factory cord is 8/3, I'd leave it, we expect reputable manufacturers to use the right parts.

 

[ritelec]

Thank you.

 

[suemarkp]

If the cord has a receptacle, note that receptacles need to follow the normal wiring rules (#8 wire and 40A breaker). If you upsize the circuit breaker larger than 40A on #8, or 50A on #6, you need to label the receptacle "Welder use Only" (210.21(B)(1)).

 

[Meltric_South]

Just a few things I can remember last time I looked at the code on welding machines.

No mention of P/R ratings, just how to specify conductors and OCPD. I've always referenced these to articles to help specify P/R when I'm helping (the most general, but I also thing the most safe and it ensure the plug will not be the OCPD).

Article 210.21(B)(1) - Single Receptacles on an Individual Branch Circuit - <paraphrasing> shall have an ampere rating not less than the branch circuit.
Article 210.18 - Branch Circuit Rating - <paraphrasing> rated in accordance with max rating or setting of OCPD

Also in regards to the disconnecting means:
If one is not mounted to the welder, one needs to be provided (can't find any requirements other than amp rating, and switch or circuit breaker). Most facilities I've been to consider the circuit breaker panel as the disconnecting means, but more and more people are adding switches close to the receptacles for safety and compliance to NFPA70E. My company gets involved because our plugs are switch-rated and safe.

 

[suemarkp]

210.21(B)(1) has this exception: Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder shall be permitted to have an ampere rating not less than the minimum branch-circuit conductor ampacity determined by 630.11(A) for arc welders.

Aren't cord/plug connections always permitted to be a disconnecting means? The breaker in the panel is limited usefulness since it needs to be "within sight" of the welder, and part of the definition limits sight to 50 feet. I don't know enough about NFPA 70E to know if that nixes cord/plugs as a disconnect for higher voltage or higher current items.

 

[Meltric_South]

210.21(B)(1) has this exception: Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder shall be permitted to have an ampere rating not less than the minimum branch-circuit conductor ampacity determined by 630.11(A) for arc welders.

So true, it helps when I read the rest of the code. I always seem to avoid the exceptions because I often feel they are used to decrease the cost of something and not used to increase safety (which I believe is the only reason to use an exception). I don't know much about the internals of a welding machine, but if there was a malfunction of the machine that allowed enough amp draw to exceed the rating of the conductors and the plug, but not trip the OCPD, I think it could create a problem <--- Devil's Advocate.

As for the cord/plug disconnecting means thing. My research shows this is dependent on the equipment or occupancy. Some things like appliances allow for plugs to be the disconnecting means, whereas the one for elevators needs to be circuit protected (which I'm not aware of plugs having this feature). The best I can tell is that if the application allows for a plug to be the disconnecting means it will specifically say its allowed. The real confusing part is when they start talking about the application-specific disconnecting means also needing to be switching or lockable or rated in HP which not all plugs and receptacles meet, depending on who you ask.

Also I only mentioned NFPA70E because a lot of the real issues happen in how the things get used once they are installed, which isn't covered in NEC.