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#77088 - 04/22/01 08:58 AM Minimum # of circuits, commercial
Tom Offline

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
We seem to have covered the minimum number of dwelling circuits quite well.

Let's try a differant exercise.

5000 square foot repair facility for left handed widgets. No hazardous locations, widgets are not self propelled & do not use any type of fuel. Heating is done with a woodburning stove, air conditioning is accomplished by opening the doors. All work is done with hand tools, you know, cordless hammers, the original cordless screwdrivers, etc. In other words, there are no other electrical loads that you know of.

Service is 200 amp, single phase overhead. Customer asked you for a code minimum job, jumped on your price, then complained about your installation (or lack of one) when you were done.

What's the minimum # of circuits for this building?

Few things are harder to put up with than the annoyance of a good example.

2014 / 2011 NEC & Related Books and Study Guides
#77089 - 04/22/01 11:02 AM Re: Minimum # of circuits, commercial
Bill Addiss Offline

Registered: 10/07/00
Posts: 4196
Loc: NY, USA

OK, always liked Widgets.. let me start.
  • 1 circuit for the light by the Panelboard.
  • 1 circuit for the show window outlet(s)(if exists)
  • Pay the Bill?

What's a "cordless hammer" ?


#77090 - 04/22/01 11:23 AM Re: Minimum # of circuits, commercial
Glenn Offline

Registered: 01/17/01
Posts: 78

Did you consider 600-5 ?

What is needed to meet Building codes, such as Exit signs?


#77091 - 04/22/01 02:36 PM Re: Minimum # of circuits, commercial
sparky Offline

Registered: 10/18/00
Posts: 5545
Tom, this is great ! how low can we go??

let's say it falls under Industrial Commercial (loft) buildings @ 2watts per sq ft
5000 x 2= 10,000w
let's give Glenn 220-3(b)(6) 1200w of it
( good call Glenn)

for the remaining 8800w, let's use 210-23(b), because this guy has no power tools !
I'm gonna run a 240v 30a lighting circuit(s)

strict 240, can't catch me up in 210-4 here

240v x 30a= 7200
damn, gotta make it two!

so 3 circuits is my best shot!

[This message has been edited by sparky (edited 04-22-2001).]

#77092 - 04/22/01 04:02 PM Re: Minimum # of circuits, commercial
wayne Offline

Registered: 04/04/01
Posts: 55
Loc: NC
Tom, I like the way Bill describe it.

1 circuit for the lights

1 circuit for the outlets

Pay the bull.
You could not make it more simple than that.


#77093 - 04/22/01 07:56 PM Re: Minimum # of circuits, commercial
Bill Addiss Offline

Registered: 10/07/00
Posts: 4196
Loc: NY, USA

After reading the 'specs' again I'm going to say with the information given that my guess would be down to 1 circuit.

You don't mention it being a store so I'm taking out the Show window circuit.


The way I'm figuring is that Our 'specs' say a repair facility. This could even be a portion of a larger building which is not 'accessible to pedestrians' and therefore would not need any Sign or outline lighting.


Aren't those the requirements for sizing the service? I don't see any required lighting or receptacles like there are in Dwellings.


#77094 - 04/22/01 09:54 PM Re: Minimum # of circuits, commercial
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
This is definitely an interesting thread.

Kind of funny that a Commercial location would only require that 1 circuit for lighting and recepts, whereas the minimums for a house are 5 circuits [it's 5 circuits, or is it more / less??].
But that's the minimum requirements.

Love the scenarion explainations, Tom!! Mind if I use them in some Hypotheticals in the future?? - mostly in the field, but possibly in the BB's.

Ya, the VA/sq. ft. stuff is to figure the minimum ampacity / load demand on the feeders. The receptacles [at 180 VA / duplex] would be added to this lighting load, then figured by demand factor [since there's so few, the demand would be 100%].

I would imagine that, following the order of all the other conveniences - the lighting would be from either gas lamps, or burning trashcans. Once again, no lighting loads
But there might be an exception to this, as pointed out by another person - illuminated exit signs.
That would depend on the UBC and local Building, Electric and Fire/Life/Safety codes. If there is no overriding code, then no illuminated exit signage needed.

Add 600-5 since it looks like the building is at least somewhat a stand-alone deal, by having it's own 200 amp service [I'm grasping at straws].
So that's one exterior lighting / sign circuit.

If exits are needed: 3 circuits [1 recepts/lights, 1 exterior, 1 exits]. then send out Invoice.

If no exits: 2 circuits, then Invoice.

Scott SET
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#77095 - 04/23/01 05:20 AM Re: Minimum # of circuits, commercial
Tom Offline

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
I suppose I could have been a little more clear. Only the NEC counts, other codes need not apply, which you would know if I told you this would be built in WV, outside of city limits.

A strong case can be made for Glenn's 600-5(a). This is one that is usually missed or ignored. I realize the Mountain State is so steep that we'll sell you both sides of the same acre, but you can pretty much walk up to any building. I don't believe that "accessible to pedestrians" is defined in the NEC, so taken very liberally, the circuit is required. Of course, Bill has a point that this might be part of a larger facility, but it would have to be completely surrounded by that facility with no exterior doors of its own (I think?).

Sparky's calculations seem fine to me. 210-11 requires the branch circuits to be provided based on the calculations in 220-3. 210-11(a) tells us how to calculate the number of required circuits. I think that 2 is the answer. Install the minimum number of circuits and one light fixture near the panel to comply with 110-26(d).

Therefore- 3 circuits is all that are required in this building.

Cordless hammer- plain old hammer, no batteries. When someone asks to borrow my cordless screwdriver, I hand them a 4" long Klein straight blade, after all, there is no cord.

Scott, help yourself. I didn't use right handed widgets because they are powered by Plutonium 240 which puts out a lot of btu's & would have required a real HVAC system.

I've used this example on occaision (or one like it), to show that wiring a house can be a lot more complicated that wiring a commercial building. This really hits home when you realize that this building doesn't even require 1 plain old 120 volt receptacle anywhere in the building. Compare that to one every twelve feet in most rooms of a house.


[This message has been edited by Tom (edited 04-23-2001).]
Few things are harder to put up with than the annoyance of a good example.

#77096 - 04/23/01 05:51 AM Re: Minimum # of circuits, commercial
Bill Addiss Offline

Registered: 10/07/00
Posts: 4196
Loc: NY, USA

I was kidding about the Hammer. I'll go through your reasoning later with that fine-toothed comb as is our custom here.

Just a quick comment. If the Building entrance is through a Common hallway and has no outside walls except for a rear Roll-up door for deliveries I would say that it would fit the bill for not being acessible by pedestrians as per 600-5. Could even be on the 10th floor. Just the fact that you did not describe the building means that almost anything can be possible.. right?



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