Conductors of different "systems" and/or "services"

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aramg83

Member
Aside from 700.9 requiring the conductors of legally defined emergency systems to remain separate from all others, does anywhere in the NEC require that conductors from and of the following cases be run separately:

1) 2 different normal power services? What about conductors downstream from the services after they have been switched/protected a couple of times?
2) 2 different separately derived systems?
3) 2 "emergency" systems, each being switched by a different ATS which gets normal and emergency feeds from different services/systems?

Thanks
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
You can't mix emergency systems that are supplied from different sources. It appears to me that item #3 includes emergency circuits from multiple sources.
 

Strife

Senior Member
1: NO, different services, different conduits.
2: Being a derived system, is as having two different services. See #1. Granted some people missunderstand separately derived systems. Do you have a switched neutral or a solid neutral? If it's switched then is separately derived, if it's solid it's not.
3: Again refer to #1. You mention different systems (which kinda sorta what a separately derived system is)


Aside from 700.9 requiring the conductors of legally defined emergency systems to remain separate from all others, does anywhere in the NEC require that conductors from and of the following cases be run separately:

1) 2 different normal power services? What about conductors downstream from the services after they have been switched/protected a couple of times?
2) 2 different separately derived systems?
3) 2 "emergency" systems, each being switched by a different ATS which gets normal and emergency feeds from different services/systems?

Thanks
 

Smart $

Esteemed Member
Location
Ohio
1: NO, different services, different conduits.
2: Being a derived system, is as having two different services. See #1. Granted some people missunderstand separately derived systems. Do you have a switched neutral or a solid neutral? If it's switched then is separately derived, if it's solid it's not.
3: Again refer to #1. You mention different systems (which kinda sorta what a separately derived system is)
1. Offhand do not know of any prohibition concerning service conductors of different systems other than stated in #2 below.

2. Conductors 600V or less of different systems can share the enclosure, cable, or raceway: ref 300.4(C)(1). Generally conductor circuits over 600V cannot share the same enclosure, cable, or raceway. Refer to 300.4(C)(2) for otherwise permitted conditions.

3. 700.9(B) Wiring, in part says, "Wiring of two or more emergency circuits supplied from the same source shall be permitted in the same raceway, cable, box, or cabinet. Wiring from an emergency source or emergency source distribution overcurrent protection to emergency loads shall be kept entirely independent of all other wiring and equipmentequipment, unless otherwise permitted..." See 700.9(B) for details of "otherwise permitted".
 

Smart $

Esteemed Member
Location
Ohio
...

2. Conductors 600V or less of different systems can share the enclosure, cable, or raceway: ref 300.4(C)(1). Generally conductor circuits over 600V cannot share the same enclosure, cable, or raceway with conductors of 600V or less systems. Refer to 300.4(C)(2) for otherwise permitted conditions.

...
#2 should have read as modified in quote.
 
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