I have been in a discussion on another board in regards to wiring for welders. I have a not so easy feeling about the gentleman?s analyses below. Guess it would be OK if the welder is the only thing he will use the circuit for. What are your thoughts on this. Thanks mlandy
Hobart Handler 180
The nameplate tells me that it has a 30% duty cycle and a 20A input current rating.
Everything you've learned to this point goes right out the window as far as sizing wire size and breaker for a given load. Welders are special, and have their own rules. (so do motors, but we're not going down that road right now)
Per table 630.11 (A)
We find that we can reduce the amp output by a multiplying factor of .55 for a non-motor generator type of arc welder.
So we multiply the input current of 20A by the multiplication factor of .55 and reach a current rating of 11A
20A x .55 = 11A
We size the conductors for this ampacity rating. In this instance, a #14 conductor is sufficient. Taken from the 60* column of the table 310.16.
FYI - You find your wire size from the 60* column when a load is under 100A per 110.14 (C)
With #14 wire, we have to keep our circuit no more than 50? from the source (panel) to keep our voltage drop under the prescribed 3% allowed by the NEC per 210.19 (A)(1) FPN No. 4.
We use the formula -
VD = 2 x K x L x I
. . . . . . . . D
Assuming:
VD = Voltage Drop
K = Resistivity of Conductor (found in Table 8)
L = Length of the circuit, one way
I = Current in conductor (amperes)
D = Cross section of conductor (in circular mils, also found in Table 8)
Now, we know that if it?s within 50?, we can use our #14 wire.
Let?s size our over current protection (circuit breaker). 630.12 (A) tells us that our over current protection shall be rated or set at not more than 200% of the rated primary current of the welder (20A). This makes our maximum circuit breaker size a 40A.
(Note ? the nameplate or owners manual will suggest an over current protective device ampacity. MOCP (Maximum Over Current Protection) if it is on the nameplate. Use this information only if it?s not available on the nameplate or owners manual.)
Let?s look for our equipment grounding conductor size. We?ll start with Table 250.122. This table tells us that #12 is needed for a grounding conductor on a 20A load.
Now we know that we need 2 - #14 and 1 - #12 for circuit conductors. Let?s size our conduit. We?ll assume EMT for our conduit.
Looking at Annex C, Table C1 ? we find that ?? EMT is good for 9 #12 THHN conductors. Since the #12 is our largest conductor, and we only have a total of 3 conductors, we?ll go with the ?? EMT for our raceway.
In summary:
For a Hobart Handler 180
So long as we keep our total circuit length under 50?, we can use 2 #14 and 1 #12 for our wire size, and a maximum of a 40A circuit breaker.
__________________
Hobart Handler 180
The nameplate tells me that it has a 30% duty cycle and a 20A input current rating.
Everything you've learned to this point goes right out the window as far as sizing wire size and breaker for a given load. Welders are special, and have their own rules. (so do motors, but we're not going down that road right now)
Per table 630.11 (A)
We find that we can reduce the amp output by a multiplying factor of .55 for a non-motor generator type of arc welder.
So we multiply the input current of 20A by the multiplication factor of .55 and reach a current rating of 11A
20A x .55 = 11A
We size the conductors for this ampacity rating. In this instance, a #14 conductor is sufficient. Taken from the 60* column of the table 310.16.
FYI - You find your wire size from the 60* column when a load is under 100A per 110.14 (C)
With #14 wire, we have to keep our circuit no more than 50? from the source (panel) to keep our voltage drop under the prescribed 3% allowed by the NEC per 210.19 (A)(1) FPN No. 4.
We use the formula -
VD = 2 x K x L x I
. . . . . . . . D
Assuming:
VD = Voltage Drop
K = Resistivity of Conductor (found in Table 8)
L = Length of the circuit, one way
I = Current in conductor (amperes)
D = Cross section of conductor (in circular mils, also found in Table 8)
Now, we know that if it?s within 50?, we can use our #14 wire.
Let?s size our over current protection (circuit breaker). 630.12 (A) tells us that our over current protection shall be rated or set at not more than 200% of the rated primary current of the welder (20A). This makes our maximum circuit breaker size a 40A.
(Note ? the nameplate or owners manual will suggest an over current protective device ampacity. MOCP (Maximum Over Current Protection) if it is on the nameplate. Use this information only if it?s not available on the nameplate or owners manual.)
Let?s look for our equipment grounding conductor size. We?ll start with Table 250.122. This table tells us that #12 is needed for a grounding conductor on a 20A load.
Now we know that we need 2 - #14 and 1 - #12 for circuit conductors. Let?s size our conduit. We?ll assume EMT for our conduit.
Looking at Annex C, Table C1 ? we find that ?? EMT is good for 9 #12 THHN conductors. Since the #12 is our largest conductor, and we only have a total of 3 conductors, we?ll go with the ?? EMT for our raceway.
In summary:
For a Hobart Handler 180
So long as we keep our total circuit length under 50?, we can use 2 #14 and 1 #12 for our wire size, and a maximum of a 40A circuit breaker.
__________________
