Arc welders breaker and cable sizing

[hhsting]

I have two types of arc welder. Each of the welders are individually fed from separate branch circuits panelboard with respective branch circuit breakers:

1. Resistance type with following:

a. Input rated current of 144A manually operated non automatic welder

2. Arc welder type with following:

a. Input rated current of 26A and duty cycle of 60%



For resistance type the cable and overcurrent protection is sized as follows:

a. 144x0.5 (since this is non automatic welder per NEC 2014 section 590.31(A)(1))= 72A so #4 cable is used

b. 144Ax2 (per NEC 2014 section 630.32(A))= 288A next higher standard would be 300A


For arc welder type cable and overcurrent protection is sized as follows:

a. Input rated current 26A so #10 AWG is used
Per NEC 2014 section 630.11(A)

b. 26A x 2 (Per NEC 2024 section 630.12(A))= 52A next size is 60A.


Questions:

1. For resistance welder if 300A breaker is used and #4 AWG which is 85A ampcity then would it comply with NEC 2014 section 630.32(B) since 300/85 would be greater than 300%? Want to verify if cable and breaker sizes are correct or not.

2. For arc welder are the cable sizes and breaker sizes #10 and 60A seem to comply with NEC 2014 sections 630.11 and 630.12 or not?

3. Can one use 35A as breaker size for Arc welder and still comply with NEC 2014 sections 630.11 and 630.12 or not?

 

[hhsting]

I have two types of arc welder. Each of the welders are individually fed from separate branch circuits panelboard with respective branch circuit breakers:

1. Resistance type with following:

a. Input rated current of 144A manually operated non automatic welder

2. Arc welder type with following:

a. Input rated current of 26A and duty cycle of 60%



For resistance type the cable and overcurrent protection is sized as follows:

a. 144x0.5 (since this is non automatic welder per NEC 2014 section 590.31(A)(1))= 72A so #4 cable is used

b. 144Ax2 (per NEC 2014 section 630.32(A))= 288A next higher standard would be 300A


For arc welder type cable and overcurrent protection is sized as follows:

a. Input rated current 26A so #10 AWG is used
Per NEC 2014 section 630.11(A)

b. 26A x 2 (Per NEC 2024 section 630.12(A))= 52A next size is 60A.


Questions:

1. For resistance welder if 300A breaker is used and #4 AWG which is 85A ampcity then would it comply with NEC 2014 section 630.32(B) since 300/85 would be greater than 300%? Want to verify if cable and breaker sizes are correct or not.

2. For arc welder are the cable sizes and breaker sizes #10 and 60A seem to comply with NEC 2014 sections 630.11 and 630.12 or not?

3. Can one use 35A as breaker size for Arc welder and still comply with NEC 2014 sections 630.11 and 630.12 or not?

Anyone post #1 opinion or thoughts thanks

 

[Bluegrass Boy]

I’m not sure if this will help your situation, but it may give you a starting point to go by, and proceed from there. Scroll to page 8 and check the examples given. If this raises any concern to your original plan, I would recommend contacting the manufacturer of the equipment and go from there.

 

[hhsting]

No that does not help much. So let’s take the arc welder.

Single Arc welder is by Western Arctronics and following:

1. 208V, single phase
2. Rated Primary Current: 144A pinned at 90A
3. Max open circuit voltage: 10,000A @Short Circuit
4. Rated Second current: 30kva @4.0vdc
5. Basis of rating: 50% of Rated Primary


So what the plans show is that according to NEC 2014 section 630.31(A)(1) for manually operated non automatic welder ampacity of supply conductor can be 50% of rated primary current. Thus 144Ax50% =72A so #4 AWG is used.

Plans show For breaker sizing NEC 2014 section 630.32(A)(B): 144x200%= 288A so uses 300A breaker.

However with breaker sizing concern is 630.32(B) #4 AWG supply conductors ampacity is 85A and breaker set at/supply conductor ampacity is 300/85=3.52 which is 352% while that section requires not more than 300%. So breaker is oversized no?

Would the above be correct that’s usually how it’s done? Is anyone familiar please verify?

 

[hhsting]

No that does not help much. So let’s take the arc welder.

Single resistance welder is by Western Arctronics and following:

1. 208V, single phase
2. Rated Primary Current: 144A pinned at 90A
3. Max open circuit voltage: 10,000A @Short Circuit
4. Rated Second current: 30kva @4.0vdc
5. Basis of rating: 50% of Rated Primary


So what the plans show is that according to NEC 2014 section 630.31(A)(1) for manually operated non automatic welder ampacity of supply conductor can be 50% of rated primary current. Thus 144Ax50% =72A so #4 AWG is used.

Plans show For breaker sizing NEC 2014 section 630.32(A)(B): 144x200%= 288A so uses 300A breaker.

However with breaker sizing concern is 630.32(B) #4 AWG supply conductors ampacity is 85A and breaker set at/supply conductor ampacity is 300/85=3.52 which is 352% while that section requires not more than 300%. So breaker is oversized no?

Would the above be correct that’s usually how it’s done? Is anyone familiar please verify?

Previous post edited its resistance welder Not arc welder. Please see above as modified

Would the above be correct that’s usually how it’s done? Is anyone familiar please verify?