Are you saying that a short circuit qualifies as a "failure of any individual lighting element" per 700.16?
No issues with 700.15 IMO. IBC specifies minimum requirements for emergency egress lighting, but there are no limits on maximum levels. Lighting the path of egress to 25 FC instead of 1 FC is permitted.
I read 700.17(2) as permitting the design. Of course how I read it does not matter so much as how the AHJ reads it, so if he is agreeing with you then maybe I am wrong.
I guess my next question would be, if this design is not permitted then why is 2017 NEC adding 700.25 permitting BCELTSs?
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What is the benefit to wiring \ activating all of the egress
lighting versus say 50% of the fixtures ?.......Would the 50%
provide sufficient lighting to egress the space ?
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700.17 is a tough read for sure. But I took a little more time to read it again, and I read the handbook commentary. I think the basic requirement is that there must be two separate branch circuits present. The handbook talks about "failure of a single branch circuit" and explains that should not leave an area in darkness. I believe your GTD device is supplied from 2 separate branch circuits, and therefore it does meet the requirement of 700.17(1).
700.17(2) would be the more standard installation, where there is normal lighting from a normal branch circuit, and emergency lighting from an emergency branch circuit.
In summary, I still don't think putting all the lights on the GTD complies due to 700.15. Just enough lights on the GTD to get your 1 FC average, and then I think it would be good.
As for the reason - in this case the Owner requested this, plus there is some savings in only having to run a single conduit down the corridor (from the GTD20 to the light fixtures is an emergency branch circuit).
There is a good article at http://iaeimagazine.org/magazine/201...hting-control/
The more they overthink the plumbing, the easier it is to stop up the drain