Emergency lighting question

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johnsciolino

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Based on your interpretation of NEC 700.9 (B), do you think it is 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 your 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-
 
That is an interesting proposal. Possible trouble with 700.9(A), before we get to (B) at all. The branch could be run without junction boxes, though.

The 'unless otherwise permitted' clause may allow for such in Sub-section 700.9(B)(1).
 
JMO

I had to go look up the word "topology" and frankly in my thoughts I found that your trying to make these items go with topology which is a network of some inter-connection (be it a broad definition and my summary of it.)

700 say's what it say's;no interconnection to other circuits, it needs to be run and dressed out accordingly, and there no interfacing trick's or gimmick of or for networking or topology to other systems.

It is it's own network, you bet, of and for an end result, but again it's not to be a topology circuit!
 
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johnsciolino said:
Based on your interpretation of NEC 700.9 (B), do you think it is 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 your 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-
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I use this relay to do transfers to inverter power for gated entrance systems, the only way I can see it comply would have to be like was said, the lighting circuit would have to be ran in its own raceway from the point of transfer to the fixture, and have no interconnecting neutrals. also the GTD-20 I use has a 30 second time delay, if yours does too, it would not comply with 700.12
 
John, maybe I am misreading the post but what exactly does 'a group of luminaries' mean? To me that sounds like all the fixtures for a certain area.

We cannot just decide to place an entire group of fixtures on the emergency supply, only the code required egress lighting can be connected to the emergency supply.

Typically this means in a large space maybe only one fixture in ten will be connected to the emergency supply.

Because of that local switching and dimming becomes quite a pain to implement. Some lighting controls are set up for this but they need to be listed for emergency system use.
 
The GTD-20A is evaluated to UL1008 and is listed as Transfer Switch Equipment. 700.9(B)(1) will allow the wiring from the emergency source and normal source to enter this enclosure.
 
I could not find a listing under WPWR (Transfer Switches)for the GTD-20A. I was able to find it under FTBR (Emergency Lighting and Power Equipment). Based on this, I gave you the wrong reference. It should have been 700.9(B)(4). Sorry about that, I should have verified the listing.
 
What if we twist it around and ask if the emergency lighting (and its wiring) can be used for normal illumination when it's not an emergency?
 
LarryFine said:
What if we twist it around and ask if the emergency lighting (and its wiring) can be used for normal illumination when it's not an emergency?
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I do not see it making a difference.

700.9(B) Wiring.

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 equipment, unless otherwise permitted in (1) through (5):

(1) Wiring from the normal power source located in transfer
equipment enclosures

(2) Wiring supplied from two sources in exit or emergency
luminaires

(3) Wiring from two sources in a common junction box,
attached to exit or emergency luminaires

(4) Wiring within a common junction box attached to unit
equipment, containing only the branch circuit supplying
the unit equipment and the emergency circuit supplied
by the unit equipment

(5) Wiring from an emergency source to supply any combination
of emergency, legally required, or optional
loads in accordance with (a), (b), and (c):

a. From separate vertical switchboard sections, with or
without a common bus, or from individual disconnects
mounted in separate enclosures.

b. The common bus or separate sections of the switchboard
or the individual enclosures shall be permitted
to be supplied by single or multiple feeders without
overcurrent protection at the source.

Exception to (5)(b): Overcurrent protection shall be permitted
at the source or for the equipment, provided the overcurrent
protection is selectively coordinated with the downstream
overcurrent protection.

c. Legally required and optional standby circuits shall
not originate from the same vertical switchboard
Click to expand...
 
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