What size wire for welder?


Old 03-09-11, 04:53 PM
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Question What size wire for welder?

I would like to get my welder off the porch and into the shop. It is a Miller M180, 230 volt, 37 amp, 180 max amp, single phase stick welder. I need to know what size wire I need to run for it. About 60' will be under ground and 60' not. The welder will be the only thing on it, and only used a few times a month. I have some 10/3 copper for underground, will that be heavy enough or do I need to get something heavier?
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Old 03-09-11, 06:36 PM
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#8 would be min.with #8 you will be at 3% voltage drop
Old 03-09-11, 08:18 PM
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The remarks in the following paragraphs are moot if the shop is detached and already has power to it. It isn't code compliant to run another feed. Your going to have to install a subpanel and abandon the existing feed.

I have some 10/3 copper for underground, will that be heavy enough or do I need to get something heavier?
You might squeak by on number 10 and a 30a breaker depending on duty cycle but #8 and a 40 amp breaker as suggested by oleguy would be better especially given the distance.
II. Arc Welders
630.11 Ampacity of Supply Conductors. The ampacity of
conductors for arc welders shall be in accordance with
630.11(A) and (B).
(A) Individual Welders. The ampacity of the supply conductors
shall be not less than the I1eff value on the rating
plate. Alternatively, if the I1eff is not given, the ampacity of
the supply conductors shall not be less than the current
value determined by multiplying the rated primary current
in amperes given on the welder rating plate by the factor
shown in Table 630.11(A) based on the duty cycle of the
(B) Group of Welders. Minimum conductor ampacity
shall be based on the individual currents determined in
630.11(A) as the sum of 100 percent of the two largest
welders, plus 85 percent of the third largest welder, plus
70 percent of the fourth largest welder, plus 60 percent of
all remaining welders.
Exception: Percentage values lower than those given in
630.11(B) shall be permitted in cases where the work is
such that a high-operating duty cycle for individual welders
is impossible.
FPN: Duty cycle considers welder loading based on the use
to be made of each welder and the number of welders supplied
Table 630.11(A) Duty Cycle Multiplication Factors for Arc
Duty Cycle
Multiplier for Arc Welders
100 1.00 1.00
90 0.95 0.96
80 0.89 0.91
70 0.84 0.86
60 0.78 0.81
50 0.71 0.75
40 0.63 0.69
30 0.55 0.62
20 or less 0.45 0.55

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