Branch Circuit receptacle loads

[muhandas]

I know that this sounds like something that was settled in the dark ages but I have a somewhat different twist on the problem.

Non-residential occupancy. Consider a branch circuit with a string of dedicated receptacles that serve instruments that are unlikely to be moved. All instruments may be used simultaneously but each instrument draws only about 0.5A at 120V, that is, about 60W. For load calculations in the context of NEC 220.14 would it be permissible to calculate the number of allowable receptacles on the branch circuit by using 60W for each receptacle load, rather than the 180W indicated in 220.14(J), since these receptacles are dedicated to known loads and are not general purpose?

On the one hand, logic would tell me yes since I know the loads, on the other hand I can't find anything in the Code that would allow that.

Would appreciate your usual incisive setting me straight.

Heinz R.

 

[jwjrw]

You have to assume these people may not be the owners in the future so the code makes you do it to a standard I think.

 

[Dennis Alwon]

Unfortunately, the code is not logical and I believe you must use 180VA.

 

[muhandas]

It is unlikely that owners would change but possible, of course. It is a laboratory in a University.

 

[Dennis Alwon]

What about this option. Plug strips with recep. every 6 inches

220.14(H) Fixed Multioutlet Assemblies. Fixed multioutlet assemblies used in other than dwelling units or the guest rooms or guest suites of hotels or motels shall be calculated in accordance with (H)(1) or (H)(2). For the purposes of this section, the calculation shall be permitted to be based on the portion that contains receptacle outlets.
(1) Where appliances are unlikely to be used simultaneously, each 1.5 m (5 ft) or fraction thereof of each separate and continuous length shall be considered as one outlet of not less than 180 volt-amperes.
(2) Where appliances are likely to be used simultaneously, each 300 mm (1 ft) or fraction thereof shall be considered as an outlet of not less than 180 volt-amperes.

 

[muhandas]

I understand but let's change the conditions a little just to test the illogic. Suppose I know that the dedicated loads connected to the receptacles will be a 1KW each. Do I still use 180W or would I use the higher value because of "...not less than 180VA..." in 220.14(J)?
In other words, the lowest load figure can be used for each yoke is 180VA even if the dedicated load is known, but if the loads are known to be greater than 180VA then the actual values should be used.
Is that one the right track?

 

[chris kennedy]

Whats wrong with 220.14(A)? I have used this many times and have had EE's as-built this on to plans for specific circuits.

 

[muhandas]

Yes, I looked at 220.14(H) but the spacing of these receptacles will be about 6ft apart.
That would force each receptacle load to be calculated at 6 x 180 = 1080W. That struck me as an even less logical option.

 

[fishin' electrician]

I understand but let's change the conditions a little just to test the illogic. Suppose I know that the dedicated loads connected to the receptacles will be a 1KW each. Do I still use 180W or would I use the higher value because of "...not less than 180VA..." in 220.14(J)?
In other words, the lowest load figure can be used for each yoke is 180VA even if the dedicated load is known, but if the loads are known to be greater than 180VA then the actual values should be used.
Is that one the right track?

Yes, because the wording is "shall be calculated at not less than 180 VA".

 

[muhandas]

Chris:
220.14(A) looked like the OK for me do just what you suggest but my hang-up was "...or other load NOT covered in (B) through (L) ..." and receptacles are in (H) so I didn't know if I could continue to the last part of (A) "...based on the ampere-rating of the ...load served."

 

[muhandas]

Should have said "...are in (J).." not H.

 

[fishin' electrician]

Should have said "...are in (J).." not H.

Yeah I thought you were in I.:roll: But it still says not less than.

 

[muhandas]

My apologies, things are happening quickly (but not my fingers and obviously, not my brain, either).
You are right, Fishin', it should have been (I) in my note concerning why I was afraid to apply the last sentence of (A).

 

[fishin' electrician]

At least 180 VA is still fairly low:grin:

 

[Dennis Alwon]

Whats wrong with 220.14(A)? I have used this many times and have had EE's as-built this on to plans for specific circuits.

Since a receptacle is covered in other parts of this article then I would say (A) may be talking about a direct wired appliance not receptacles. On the other it is ambiguous at best and it may be the intent to cover recep. for specific equipment.

 

[muhandas]

Thanks a lot for the usual great discussion.
Obviosly, the issue is what is the fewest number of circuits that need to be dragged into that Lab.
I agree with you, Dennis, about the ambiguity of (A) and also agree with Chris' position - this just makes more sense. I'll base my rationale on that and if I get a lot of static I'll back off to 180VA per receptacle.

There is a part 2 to this but I won't lumber you guys with it just yet. Maybe Monday when I get to the job site.

 

[kwired]

you could possibly put other receptacles away from your light load equipment in the lab on the same circuit if number of branch circuits is an issue.

 

[muhandas]

That's certainly an option to fall back on if I have to.
Tx.