Treating joined occupancies as one, electrically

[kwired]

The way I see it is if the two "buildings" are joined together then it is one structure for art 230 purposes and general rule is you can only supply it with one service, which can consist of up to 6 disconnecting means. Then the allowances for multiple services or additional disconnecting means kick in if certain conditions are met. Multiple occupancies is one of those conditions/allowances. Chances are other codes have requirements as well if it is going to be considered multiple occupancy, like fire ratings between each occupancy.

Have had major additions to facilities around here that are essentially a separate building but connect to the existing facility via a short enclosed corridor, sometimes very short corridor or even a common wall with existing facility. Many times the EI allowed separate service to the addition but wanted a 2 hour rating between the two "buildings", and/or automatic closing fire doors at common openings, which the fire marshal likely required anyway. But one building was not allowed to supply circuits in the other building

 

[kwired]

By the NEC's definition of Building - "A structure that stands alone or that is separated from adjoining structures by fire walls," this situation is two adjoining buildings.

Which opens the door to allowing separate service to each "building" but at same time does not mean you must have separate service to each

 

[mtnelect]

This might help to explain.

 

[JoeStillman]

By the NEC's definition of Building - "A structure that stands alone or that is separated from adjoining structures by fire walls," this situation is two adjoining buildings.

Ok, then do we have to consider all stair towers separate buildings? How about a transformer vault? They are always separated from the adjoining structure by fire walls.

 

[infinity]

Ok, then do we have to consider all stair towers separate buildings? How about a transformer vault? They are always separated from the adjoining structure by fire walls.

Yeah it starts to get ridiculous when you plop down firewalls and everyone says that your single structure is really 50 separate buildings.

 

[andrew1]

How is it adjudicated in townhomes or crowded street blocks where walls are shared? That is not a field I am familiar with. Is it based on some architectural or structural declaration?

 

[JoeStillman]

How is it adjudicated in townhomes or crowded street blocks where walls are shared? That is not a field I am familiar with. Is it based on some architectural or structural declaration?

We deal with that question a lot. The same building plan could be judged one building or several, depending on the division of occupancy.

So imagine a row of townhouses. There is a 2-hour firewall between all the units. If the firewalls lie on a property line so each townhouse has a different deed, then the utility has to run a line on the outside and enter each house separately.

Now imagine the same building without the property lines, but condominium ownership. The condo owners only own from "paint to paint"; all the stuff inside the walls is under common ownership. In this situation, we install a meter center at one end (or both ends) and the units are not fed by services. They each have a utility meter, but the circuit feeding each house is a feeder and not a service. (We have to run an EGC, and the neutral is bonded at the meter center, not the panel.) The SER cables run in the joist space and get fire stopped at all the fire walls. But it's not considered a building that's fed "through another building". It's all one building for our purposes, and we usually have a main disconnect in the meter center.

We often design services to multi-family buildings that are so large, the utility company needs more than one pad-mount to feed it. Each dwelling unit is separated by firewalls from all the units around it, but they are not considered "buildings". And we are allowed to have multiple services in different locations by 230.2(B)(2) or 230.2(C).

We try to avoid defining the term "building" in discussing these situations. Nobody has a single definition that works every time.

 

[JoeStillman]

I guess the best thing I can say about the definition of "Building" in the code is that it's there if you need it, but you don't have to use it just because it's there. I hereby confess my heresy and seek absolution.

 

[jim dungar]

Yeah it starts to get ridiculous when you plop down firewalls and everyone says that your single structure is really 50 separate buildings.

My take is: the presence of fire walls, alone, does not cause there to be separate buildings, however the lack of firewalls prevents there from being separate buildings.

How many fire walls exist in a typical hospital? We know each area does not have its own 'emergency' system.

 

[Elect117]

How is it adjudicated in townhomes or crowded street blocks where walls are shared? That is not a field I am familiar with. Is it based on some architectural or structural declaration?

They have different addresses, different owners, and most likely different parcels.

 

[kwired]

How is it adjudicated in townhomes or crowded street blocks where walls are shared? That is not a field I am familiar with. Is it based on some architectural or structural declaration?

NEC has provisions to run separate services to multi occupancies and doesn't really refer to fire ratings when considering this, but your other codes almost always will address this and have finish rating requirements for partitions between said occupancies.

 

[kwired]

My take is: the presence of fire walls, alone, does not cause there to be separate buildings, however the lack of firewalls prevents there from being separate buildings.

How many fire walls exist in a typical hospital? We know each area does not have its own 'emergency' system.

or schools or other similar structures. Often they are more strict on finish ratings of corridors or other egress pathways than they are for offices, classrooms, patient rooms, etc. Which is why stair towers are effectively a separate building when it comes to finish ratings.

 

[infinity]

My take is: the presence of fire walls, alone, does not cause there to be separate buildings, however the lack of firewalls prevents there from being separate buildings.

How many fire walls exist in a typical hospital? We know each area does not have its own 'emergency' system.

I agree. Even in a multi-tenant building you can run circuits through different tenants spaces without having to apply the Article 225 rules for outside branch circuits and feeders.