NEC Violation

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eee

Member
The following seems undefined in the NEC as to whether it is a violation. I have a service entrance that feeds the whole building, but not one room. I have another service entrance that feeds this room not fed from the main service entrance. This room is the emergency circuit which also is on back-up generator power comming from another facility.

The NEC says you can have a separate service entrance as an exception if the second service entrance is for emergency power or standby power. I would think the assumption is that the main service entrance must feed the entire building including the other room mentioned above while the second service entrance is inactive until such time emergency power is needed from either the second source generator or the second source power for the room mentioned above.

I would hope that the first service entrance does not have to feed the whole building since that would represent my position I require to save money and meet schedule.
 

bdarnell

Senior Member
Location
Indianapolis, IN
Occupation
Retired Engineer
Maybe I haven't had enough coffee yet this morning, but I'm confused by your description of the power feeds to the building. Do you have 2 SERVICES, (i.e. meters) or do you have a service and a branch circuit or feeder from another building for your emergency circuit ?
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
One example of an emergency service is a fire pump. The fire pump is fed separate from the rest of the building and the fire pump is always fed from this second service. It is not usually switched between the normal and emergency service (although it could be). That sounds a lot like what you are talking about.

Also, is it possible your single room could be called a separate building? This might be possible if there is a fire rated wall between it and the rest of the building.

Steve
 

eee

Member
NEC Violation

Per the NEC Handbook. The purpose of permitting an emergency circuit on a second service entrance is so that reliability can be maintained for the emergency circuit in case the first service entrance fails (unfortunately my first service entrance does not provide source power to the room requiring emergency service). My emergency circuit for the separate room (which is a room inside the building) is a branch circuit from a service entrance feeding another building. This is a bizzare circuit configuration that I fear the NEC handbook, NEC Codebook, or NESC do not address.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
There is nothing in the NEC that requires every room of every building to have power at all. But just out of curiosity, what is in this room? Is it just a place for an emergency panel and a transfer switch? Are there lights and receptacles in the room, and if so where do they get their power?

Also, is this a hospital? I ask that because it is one of the few types of buildings that actually require an "emergency" power source. Most places that have backup generators do not require "emergency" power, but rather are using the generators for "optional standby" loads. The word "emergency" is very often used in situations that are not emergencies.
 

haskindm

Senior Member
Location
Maryland
I don't have a 2005 code book in front of me right now, but look at 230.2 - Number of services. There is a new section that allows additional services in order to provide a redundant source of power in the event of a failure. This may help you, but I am not sure. If I understand correctly you still have only one source of power in this additional room, so it is not really redundant. I guess we need more information about what this room is and what they are trying to accomplish by putting it on a separate service. It sounds like the designer may not understand how to provide redundant power.
 

eee

Member
NEC Violation

The room that has a separate source power is an oral surgery room in the dental clinic. It's source power comes from the medical clinic which also supplies back-up emergency power to this oral surgery room from a generator at the hospital that services the medical clinic with back-up emergency power also.
 

eee

Member
NEC Violation

I looked at the NEC and NEC handbook and interpreted this from another perspective. If the NEC permits a second service entrance, either emergency (less than 10 second recovery) or stand-by (more than 10 second recovery) as I read it, than it could be assumed that there should not be a second source service entrance (for my room in question), but only a second emergency or stand-by service entrance normally powered by a generator either in stand-by mode or in active immediate switchover mode (running as a back-up emergency energy source).
 

eeee

Senior Member
NEC Violation

Per the NEC:
EEE,

230.2 A building or other structure served shall be supplied by only one service unless permitted in 230.2 (A). Note that 230.40 says each service has a different set of service conductors (or new service entrance you would have to read from that).

230.2 (A), (2), (3), and (4) state that emergency systems, legally required standby sytems and optional standby systems can have a different service and that means different service entrance (source power or back-up generator) I would have to read from that.

Taking these above statements from the NEC at face value would indicate the first service entrance (source power from 3 phase transformer A) does not have to supply the whole building, much like the previous responder said a fire pump can be on a different service (or I would read-a different set of service entrance conductors from a different source-a different set of transformers-say 3 phase transformer B).
 
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