receptacle load for other than 5-15 and 5-20

[ducks1333]

In a laboratory environment and probably others it common to have NEMA 6-20, 6-30, and other receptacles that I consider to be general purpose outlets. There is no specific piece of equipment that is to be plugged into these outlets. Is there any place in the NEC that requires you to use other than 180 VA per outlet for the load calculation?

Thanks,
John

 

[kwired]

I think 220.14(L) answers your question. Remember it is a minimum value, you can use a higher value if you wish.

(L) Other Outlets. Other outlets not covered in 220.14(A) through (K) shall be calculated based on 180 volt-amperes per outlet.

 

[ducks1333]

That is the only reference I know of also. There is a tremendous diversity in these outlets, they are seldom used and I don't want to take them at a higher load that I have to. At 208 1 ph. that is only 90 va per phase and at 3 ph it would only be 60 va per phase. It doesn't make a lot of since but I didn't know of anything that would make me take them at more than that, unless I thought it was an inadequte design which I don't. Thanks for your input, would like to hear if any others agree or disagree.

 

[kwired]

That is the only reference I know of also. There is a tremendous diversity in these outlets, they are seldom used and I don't want to take them at a higher load that I have to. At 208 1 ph. that is only 90 va per phase and at 3 ph it would only be 60 va per phase. It doesn't make a lot of since but I didn't know of anything that would make me take them at more than that, unless I thought it was an inadequte design which I don't. Thanks for your input, would like to hear if any others agree or disagree.

I myself would probably factor in the heaviest individual load expected - especially if nothing else would likely be operating on the other receptacles at same time.

I have done many repair shops where they want welder receptacles everywhere, yet there will only be one maybe two welders used at same time - so I would only figure one or two for a load calculation even though there may be eight receptacles.

Kind of hard to weld in 8 different places when you only own 2 welders.

 

[broadgage]

If outlets larger than the normal 120 volt 15 amp or 20 amp are installed, it would seem reasonable to assume that they will be used, though not all at full capacity at the same time.

I would be inclined as a minimum to allow for 100% load on the first outlet, 50% on the second outlet, and a much lower percentage on the others.

I do not think that simply allowing 180VA per outlet is enough.
10 outlets=1,800VA, when a single fully loaded large outlet is more than that.

 

[kwired]

If outlets larger than the normal 120 volt 15 amp or 20 amp are installed, it would seem reasonable to assume that they will be used, though not all at full capacity at the same time.

I would be inclined as a minimum to allow for 100% load on the first outlet, 50% on the second outlet, and a much lower percentage on the others.

I do not think that simply allowing 180VA per outlet is enough.
10 outlets=1,800VA, when a single fully loaded large outlet is more than that.

You can do whatever you want with them as long as you include either the dedicated load if you have one, or 180 volt amps per outlet if you don't have a dedicated load. Like I said before, I have put in multiple welder outlets in shops, not because a welder will be used in every one of those outlets at same time but because they will move a welder from one location to another as needed. If only one welder is expected to ever be used at a time why use 6 or 8 welders for load calculation? The lab in the OP is possibly same way. Maybe only one or two pieces of equipment that will use these receptacles, yet there is more than one or two receptacles to allow for use in different locations. Unlike the 5-15 and 5-20 receptacles that are likely to be used by something else, these receptacles are somewhat dedicated.

I like the welder outlet example - it is typically a pretty fair amount of load for one outlet so including that load for multiple outlets in a service or feeder calculation will make a significant difference. But yet the outlets are there for convenience of moving just one welder from place to place and not for using a welder at every outlet simultaneously. I have welder outlets scattered all around in a light industrial plant also. Very seldom is there any load on them. One outlet in shop gets used most of the time as that is where welder is most often used, but they take it out into production area when needed to repair something in place. When they are used - production is usually shut down so there is likely plenty of power available for the welder, and it is only using one outlet, not all of them.