480 volts welding receptacle

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MRUGEN SHETH

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I have to provide 6 welding receptacles of 480 volts, 3 phase, 60 amps fed from PDP. Out of these 2 are considering spare/future provision. Each receptacle shall be fed by individual feeder.

I do not have the information how these receptacles shall be loaded i.e one at a time or all at a time. NEC 630 provides the information for sizing of cables and OCPD.

How do I consider the loading effect (in KVA) to determine the PDP main breaker size feeding all these receptacles (i.e spare + Inservice)

Thanks.
 
I know they are called "welding receptacles", but they are often used for construction temporary power. Since the only time they are used is when there is a project going, I've always sized the conductors for the 60A CB, didn't use the 630 sizing criteria.

Also, since the normal use is projects, and probably there is a shutdown to do the work, and the management is interested in getting the job done as soon as possible - I always figured all were in use at the same time.

My tendency is to leave enough spare capacity for the future provisioning.

But, that is just me. All the extra capacity costs money. You need to get your crystal ball out and make some productions as to how the equipment is to be used. One of the methods I use is to look at similar installations in the company. Another is to ask the ask the older project people.

carl
 
It means that no demand factor shall be considered for calculation. (spare + inservice)

125% of continuous loads i.e 60 * 6 * 1.25 = 450 amps.

So for 6 welding receptacles breaker shall be of 450 amps or 500 amps.
 
infinity said:
I agree. No human could actually weld for 3 continuous hours.
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Well theres that problem.:)

I was thinking that few welders (are there any for human use) that have 100% duty cycles.

That seems to be the entire basis for the relaxed rules in 630.
 
coulter said:
That would be true if that is what they were actually used for.

carl
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Of course but that is what the OP said they where for.:smile:

If it was used as temp power for construction that would have little continuous load either.
 
MRUGEN SHETH said:
It means that no demand factor shall be considered for calculation. (spare + inservice)...
Click to expand...
Well, designing from my side of your keyboard is tough - especially without the benefit of your crystal ball ;)

Without more information, such as the normal practices where you are, I'm uncomfortable making any recomendations. That being said, you might consider sizing branch and feeders at 100%.

If they end up being used for welding machines, iwire and infinity are correct, they (conductors and panel) are way oversize.

carl
 
I had a welding shop that made giant underground tanks, the electrodes

look like 3/8 rod, the only time they stopped was to put in another stick.

The welders were 600v 60a 3ph., my best guess would be approx. 70%

usage at full tilt. Edit; should say, I had a customer that has welding shop
 
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Speaking of welders, we have this welder that has a 4000A service just by itself. That is the honest truth. Had to have it's own HV primary run to a transformer with a meter. The thing is so big it had to have it's own zip code.
 
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