200 hp air compressor

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Jaeggie

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The owners of our facility from which we lease have installed a 200 hp 480v 3phase air compressor fed from a parellel run of 4/0 600 v welding cable ( six wires ) in a 3 1/2 " conduit run about 100 ft in length. I know the welding cable is probable not suitable for this but want to know the nec code article which prohibits it. would appreciate any help.

Jaeggie
 
I think the cable may be fine but I would bet the lugs that are used are not listed for the small strands. There are special lugs designed for different class wiring. All of that must be considered. What is the insulation and class type of the wire.
 
Unless the cable is one recongined in Section 310.13 is it not an allowable NEC wiring method. You need to check the markings on the cable.
In addition, the terminations must be listed for the type cable used as Dennis mentioned.
 
I haven't looked up the amps you need for that motor, but even though the cable has a higher temp and amp rating, the terminations at the breaker or disconnect will be rated for much less, which may be an issue with temp rise.
 
hillbilly1 said:
I haven't looked up the amps you need for that motor, but even though the cable has a higher temp and amp rating, the terminations at the breaker or disconnect will be rated for much less, which may be an issue with temp rise.
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Thanks for reply. Motor rated at 240 amps at 480v . Slide rule shows 350 MCM 75 c wire or equiv.
 
Jaeggie said:
cable reads - Presotflex Welding Cable 4/0 Ga 105 deg C/ -55 deg C Made in USA
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400.4 for listing, 400.8(6) says no to conduit, 310.13 for the correct wire.
IMO, welding cable is for welding only. Like others have stated, terminating will be a problem. It doesn't make it right just because it works.
 
Jaeggie said:
cable reads - Presotflex Welding Cable 4/0 Ga 105 deg C/ -55 deg C Made in USA
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Even if you ignore that this is non-NEC cable and that it is not agency listed for any purpose, the insulation voltage level remains a question form the purely engineering standpoint. The manufacturer does not list that information. (This is in addition to all the other good comments made.)
 
weressl said:
Even if you ignore that this is non-NEC cable and that it is not agency listed for any purpose, the insulation voltage level remains a question form the purely engineering standpoint. The manufacturer does not list that information. (This is in addition to all the other good comments made.)
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Beat me to it, I was going to say there is no voltage rating for the mentioned conductor. Even though it is marked 105 degrees it would still need to be sized according to 75 degree terminations, but I don't think this is a conductor suitable for this application anyway.

Why did they use this cable in first place - probably more expensive than what they should have used - unless they already had it for some reason.
 
kwired said:
Beat me to it, I was going to say there is no voltage rating for the mentioned conductor. Even though it is marked 105 degrees it would still need to be sized according to 75 degree terminations, but I don't think this is a conductor suitable for this application anyway.

Why did they use this cable in first place - probably more expensive than what they should have used - unless they already had it for some reason.
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Welding cable is not suitable for the purpose. The insulation will crack after being exposed to the air. Welding is not done at 480 volts. Usually 30 or less.

Welding cable is very flexible and has many fine strands. It is easy to work with. I use it on 12 volt jumper cables. After seeing what eventually happens to the insulation, no way would I try to use it with 480 volt AC.
 
K8MHZ said:
Welding cable is not suitable for the purpose. The insulation will crack after being exposed to the air. Welding is not done at 480 volts. Usually 30 or less.

Welding cable is very flexible and has many fine strands. It is easy to work with. I use it on 12 volt jumper cables. After seeing what eventually happens to the insulation, no way would I try to use it with 480 volt AC.
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The only thing that could make this more interesting would be if it is on an ungrounded system, without ground detection.
 
K8MHZ said:
Welding cable is not suitable for the purpose. The insulation will crack after being exposed to the air. Welding is not done at 480 volts. Usually 30 or less.

Welding cable is very flexible and has many fine strands. It is easy to work with. I use it on 12 volt jumper cables. After seeing what eventually happens to the insulation, no way would I try to use it with 480 volt AC.
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Where did the idea of welding cable cracking when exposed to the air come from? Welding cable is used outdoors in some of the most harsh envioronment known to man. It is exposed to chaffing,water and oil,chemicals and is designed for exactly these harsh conditions. (if it were to crack upon exposure to air why do you suppose you see service trucks of all kinds with coils of cable hanging in thier racks outside)
As far as welding being done at 30 volts or less that statement is just not correct. A stick welder like a 300 amp gas drive has an open circuit voltage of around 105 volts. When the arc is struck the voltage droops to whatever the rheostat voltage is set to normally in the 60 volt range. 30 volt welding is constant voltage and is used with typical wire feeders anywhere from 18 to 40 volts.. I believe Belden actually makes a welding cable that is rated at 600 v. The terminations on welding cable are typically a swaged copper lug and are very durable. All that being said I dont know of any welding cable that is rated within NEC requirements for power distribution wiring.
 
Most welding cable i have seen is marked 600 volts. Some is marked welding cable/RHW. This second type can be used anywhere you use RHW.
 
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