Based on interpretation of NEC 700.9 (B), is it permissible to connect a group of luminaries (not unit equipment) on a single branch circuit which are switched locally (or dimmed) to a transfer relay which upon transfer utilizes the same wiring (connected ahead of all switching) to be used as emergency lighting? Would this topology satisfy the conditions stipulated by (1)-(4) of this article?
In other words, each group of fixtures operates on a local switch under normal operating conditions, and then upon branch circuit failure the entire group of fixtures would be served from a source which is compliant with all requirements of 700.12 - but, the wiring/raceway serving the group of fixtures under emergency conditions is the same wiring/raceway which serves the fixtures under normal operation- the only difference being the source is changed (via a transfer relay connected on the circuit ahead of any local switches).
It seems to me this topology may be in conflict with the requirement in NEC 700.9(B) which stipulates ??emergency wiring must be kept entirely independent of all other wiring and equipment??. It is not clear to me how to apply NEC 700.9(B) (1)-(4) to this arrangement, and I would greatly appreciate any input.
Bodine makes a device called a GTD-20A which is essentially a transfer relay suitable for transference of a 20A branch circuit from a non-emergency source to an emergency source, it would seem such a device would not be useful if 700.9(B) (1)-(4) does not permit it?s use in this manner-
In other words, each group of fixtures operates on a local switch under normal operating conditions, and then upon branch circuit failure the entire group of fixtures would be served from a source which is compliant with all requirements of 700.12 - but, the wiring/raceway serving the group of fixtures under emergency conditions is the same wiring/raceway which serves the fixtures under normal operation- the only difference being the source is changed (via a transfer relay connected on the circuit ahead of any local switches).
It seems to me this topology may be in conflict with the requirement in NEC 700.9(B) which stipulates ??emergency wiring must be kept entirely independent of all other wiring and equipment??. It is not clear to me how to apply NEC 700.9(B) (1)-(4) to this arrangement, and I would greatly appreciate any input.
Bodine makes a device called a GTD-20A which is essentially a transfer relay suitable for transference of a 20A branch circuit from a non-emergency source to an emergency source, it would seem such a device would not be useful if 700.9(B) (1)-(4) does not permit it?s use in this manner-