Number of Outside Feeders Between 2 Sections of a Building (NEC 225.30)

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zemingduan

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Philadelphia,PA
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Electrical Designer
We have a building that has 2 sections. Section A and section B are connected by a corridor only on the 2nd floor. On the other floors, there are no connections between section A and section B. See below for the 2nd floor plan. Section A has (15) dwelling units. Section B has (15) dwelling units. The electrical service comes into section A in the basement electrical room. How can we supply the section B from the electrical room in section A? Can we have (15) 150A 1ph underground feeders from the electrical room in section A to supply the (15) units in section B? Are we only allowed to supply section B by (1) 800A 3ph feeders (the calculated loads for section B is 685A @ 3ph 208/120V) per NEC 225.30?

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AC\DC said:
Roofs attaching seems one building to me.
See what your building department says.
That will determine what you can do
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The roofs and basement are detached too. The two sections are only connected on 2nd floor.

Structure and Building are defined as below in NEC 2017:

Building. A structure that stands alone or that is separated from adjoining structures by fire walls. (CMP-1)

Structure. That which is built or constructed, other than equipment. (CMP-1)

So I am thinking that even though these 2 sections are considered as one building. But they are still two structures. You can only have one outside feeder to supply another structure per 225.30.
 
I am thinking that if we pull (15) 150A feeders inside the building through the 2nd floor corridor that connects the two sections , it is allowed. But if we run the feeder outside the building we can only use one feeder to supply the section B. That is my understanding of the article 225 and 225.30. Please let me know you guys' ideas. Thanks!
 
IMO, it is one structure. The rule about number of feeders to a structure was about how many feeders could feed the building. The number of feeders within the building does not matter, regardless of whether they are inside or outside.
 
I definitely think that the determination of whether it is one structure or two does not depend on the routing of the electrical feeders.

If what you have is something like the photo below, sounds like two buildings to me.

Cheers, Wayne

skyway_bridge_3.jpg
 
zemingduan said:
Thanks for you opinion. We have outdoor wall space in section B to put meters for sections B there.
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Your saying "Feeders" to section B, but indicating new meters for section B.

That doesn't compute.

Jap>
 
wwhitney said:
I definitely think that the determination of whether it is one structure or two does not depend on the routing of the electrical feeders.

If what you have is something like the photo below, sounds like two buildings to me.

Cheers, Wayne

View attachment 2561957
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I agree it looks like two buildings with an enclosed walkway between them, but I am not sure the building code would make it three separate structures.
 
david luchini said:
Run a feeder from Building A to a modular meter center at Building B. What doesn't compute?
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Why would you need a modular meter center if the existing service is under one management already?

Any runs from an existing switchboard would be feeder conductors not services conductors.

If service conductors are being run through one building to feed another to feed a group metering setup that's a whole different sceneario.

Sound like new Service Entrance conductors the way it is worded.

JAP>
 
jap said:
Why would you need a modular meter center if the existing service is under one management already?
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Because each tenant pays for their own electric usage.
jap said:
Sound like new Service Entrance conductors the way it is worded.
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The question was specifically running one feeder from building A to building B, vs. running 15 feeders from building A to building B.
 
david luchini said:
Because each tenant pays for their own electric usage.

The question was specifically running one feeder from building A to building B, vs. running 15 feeders from building A to building B.
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If you're talking modular metering with CT's, that would be customer owned metering and could be placed anywhere they'd be convienent could they not ?

Why would you need outdoor wall space for that type of metering?

The power company is not going to read that usage,,, the customer would have to.

JAP>
 
jap said:
If you're talking modular metering with CT's, that would be customer owned metering and could be placed anywhere they'd be convienent could they not ?
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I believe he's talking about utility metering.
jap said:
Why would you need outdoor wall space for that type of metering?
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I has to be mounted somewhere. It sounds like there is no space inside the building for it.
 
I would think each building having its own service and meter stack would be best, and tenants would have whatever access they will have will be in their own buildings.

No, I don't see a sky-walk between buildings as rendering them one structure.
 
david luchini said:
I believe he's talking about utility metering.

I has to be mounted somewhere. It sounds like there is no space inside the building for it.
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If we're talking utility metering then we are we not talking Service Conductors to the line side of the Utility Meters ?

Sub metering is installed on the load or "feeder" side of things.

JAP>
 
LarryFine said:
I would think each building having its own service and meter stack would be best and tenants would have access in their own buildings.
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Exactly, but, that's not what's being described.

If "feeders" are being discussed to be installed from Bld A to feed Bld B, then the distribution would already have to be in place in Bld A to begin with.

JAP>
 
jap said:
If we're talking utility metering then we are we not talking Service Conductors to the line side of the Utility Meters ?

Sub metering is installed on the load or "feeder" side of things.
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Not necessarily. If you have a modular meter center with a main circuit breaker, then the meters are on the "load" or "feeder" side of the main circuit breaker.

I would think "sub metering" would be installed on the load side of other metering.
 
david luchini said:
Not necessarily. If you have a modular meter center with a main circuit breaker, then the meters are on the "load" or "feeder" side of the main circuit breaker.

I would think "sub metering" would be installed on the load side of other metering.
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Yes a modular meter center with a main circuit breaker and load side meters are very common, but, generally the conductors to the line side of that setup are Service Conductors from the Utility Transformers, not a feeder from a breaker located in an existing Modular Metering Center upstream from it.


Oh well,,

Jap>
 
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