two electric welders, eight receptacles

[malachi constant]

Have a client who owns two welders. Wants to move them around their facility to different locations, so has asked for eight receptacles, all fed from a single 480V welding panel. There is no guarantee that they will not purchase more welders in the future.

Calculating the individual branch circuits is straightfoward. However our office has a disagreement as to how to calculate the overall panel load. Two options:
1. Consider this a group of eight welders, follow 630.11(B). 100% for first two welders, 85% of third welder, and so on.
2. Consider this a group of two welders. 100% for the first (only) two welders. Anything else is considered future.

Regarding the second way, we would still feed and size the panel allowing for future welders, but for the purposes of the overall building load would only be counting two welders instead of eight. May save us a service size, keep us below 1200A.

You can probably see I'm leaning towards the second. However I'm not able to cite a code section that allows me to do this. I see where they're coming from for the first option but think it is overkill to size for "ghost" equipment that is not actually there.

 

[petersonra]

where in the code are you ever required to provide for equipment that does not exist?

nothing in the calcs requires you to include loads that just plain do not exist at the time the load calculation is being made.

why would you size the panel for stuff that does not exist unless the customer asked for it and is willing to pay for it? at the very least you owe it to him to tell him you are planning to spend more of his money than is necessary to handle these two welders.

 

[malachi constant]

where in the code are you ever required to provide for equipment that does not exist

Convenience receptacles come to mind. 180VA per. Nothing may ever get plugged into it. But you have to count it.

These are, in one sense, convenience receptacles for a welder. If one were to ask "what is that receptacle for? what will get plugged in there?", the answer would be "every once in a while a welder". Repeat for eight such receptacles.

Then you go back to the panel and ask "what does that breaker feed?" the answer for each would be "every once in a while a welder".

I'm on your side, I think it is very logical to say since they only have two welders that's how the panel load gets calculated. Panel load sheet would have two breaker loads accounting for welders and six breakers with loads zeroed out, but all are labeled "welder".

I am pretty sure code speaks to this somewhere but not sure where. I would sleep a little better if I knew exactly where, that is all.