Anonymous-0
Well-known Member
This message is a reply to an archived post by JeremyR on December 31, 2008 at 15:24:34.
The original subject was "Drop cord for a welder".
A review of the spec sheet for the Hobart Handler 187 shows that it draws 20 amps at 230v while delivering its rated output of 130A. At this setting the welder is only good for a duty cycle of 30 percent.
The welder can deliver a max of 185 amps, but only at an 18 percent duty cycle. At this load, the line current would be around 28 amps.
There are four common issues when selecting a wire gauge -- resistive heating, voltage drop, code compliance, mechanical strength.
So far as resistive heating goes, 10AWG wire will be just fine. Not only are you within the nominal 30A ampacity, the duty cyle limits imposed by the welder itself mean the extension cord will never be able to heat up enough to be an issue.
Voltage drop will be fine as well. 10AWG wire has a resistance of .001 ohms per foot. Taking a 100 foot two-way length, we're looking at a voltage drop of 3.3 volts running the welder at the full-tilt 185 amps. This is within the 2% range taken as a typical goal for voltage drop in a branch circuit.
So far as code compliance goes, article 400.7(A)(3) appears to allow the use of a flexible cord to connect your welder as an "appliance". Table 400.5(A) gives an allowed ampacity of 30 amps for SJEOOW, SJOOW, etc. cords.
Welders are subject to the special provisions of article 630, which allows the use of Iieff from the welder data plate to size the supply conductors. In the alternative, one can adjust the rated primary current by a factor based on the welder duty cycle given in table 630.11(A). For a duty cycle of 30% we can use an adjustment factor of 0.55, which would nominally allow the use of 11 amps for the purposes of sizing supply conductors. At least from the standpoint of overheating and safety, it appears the code would allow 14AWG wire to be used, because the welder is an intermittent load, not drawing the rated current continuously for 3 hours. (Voltage drop and welder performance would rule out using such small wire, but the proposed 10AWG extension cord is plenty big enough).
Finally, we look at mechanical performance. Any of the proposed cordage (SJEOOW, SJOOW, SJTW) would be fine. All are rated for outdoor use (W). SJEOOW is a likely a little more flexible than the others because it is allowed for "elevator" use. (E). All are "hard service" cords, so you don't have to worry about stepping on them or running over them with shop carts, etc. All are much, much better choices than the jury-rigged 10/2 NM "farmer" extension cords one commonly sees, which "work" for a week or so before one of the solid copper conductors breaks from being flexed, or the insulation tears.
I don't see any problem using the proposed 10AWG cordage to make a 50 foot extension cord for this particular welder. As with any extension cord, one must exercise some discipline in choosing it to connect other things down the road,like air compressors or "buzz box" welders.
The original subject was "Drop cord for a welder".
A review of the spec sheet for the Hobart Handler 187 shows that it draws 20 amps at 230v while delivering its rated output of 130A. At this setting the welder is only good for a duty cycle of 30 percent.
The welder can deliver a max of 185 amps, but only at an 18 percent duty cycle. At this load, the line current would be around 28 amps.
There are four common issues when selecting a wire gauge -- resistive heating, voltage drop, code compliance, mechanical strength.
So far as resistive heating goes, 10AWG wire will be just fine. Not only are you within the nominal 30A ampacity, the duty cyle limits imposed by the welder itself mean the extension cord will never be able to heat up enough to be an issue.
Voltage drop will be fine as well. 10AWG wire has a resistance of .001 ohms per foot. Taking a 100 foot two-way length, we're looking at a voltage drop of 3.3 volts running the welder at the full-tilt 185 amps. This is within the 2% range taken as a typical goal for voltage drop in a branch circuit.
So far as code compliance goes, article 400.7(A)(3) appears to allow the use of a flexible cord to connect your welder as an "appliance". Table 400.5(A) gives an allowed ampacity of 30 amps for SJEOOW, SJOOW, etc. cords.
Welders are subject to the special provisions of article 630, which allows the use of Iieff from the welder data plate to size the supply conductors. In the alternative, one can adjust the rated primary current by a factor based on the welder duty cycle given in table 630.11(A). For a duty cycle of 30% we can use an adjustment factor of 0.55, which would nominally allow the use of 11 amps for the purposes of sizing supply conductors. At least from the standpoint of overheating and safety, it appears the code would allow 14AWG wire to be used, because the welder is an intermittent load, not drawing the rated current continuously for 3 hours. (Voltage drop and welder performance would rule out using such small wire, but the proposed 10AWG extension cord is plenty big enough).
Finally, we look at mechanical performance. Any of the proposed cordage (SJEOOW, SJOOW, SJTW) would be fine. All are rated for outdoor use (W). SJEOOW is a likely a little more flexible than the others because it is allowed for "elevator" use. (E). All are "hard service" cords, so you don't have to worry about stepping on them or running over them with shop carts, etc. All are much, much better choices than the jury-rigged 10/2 NM "farmer" extension cords one commonly sees, which "work" for a week or so before one of the solid copper conductors breaks from being flexed, or the insulation tears.
I don't see any problem using the proposed 10AWG cordage to make a 50 foot extension cord for this particular welder. As with any extension cord, one must exercise some discipline in choosing it to connect other things down the road,like air compressors or "buzz box" welders.
