Auto-throw over MTM switchboard

[anbm]

If the building main switchboard will be built with Auto-throw over MTM (main-tie-main) configuration, SWBD is fed from (2) separate Poco transformers. Do egress lights and exit signs in corridor and stairwell still need backup battery?

 

[don_resqcapt19]

Up to your AHJ.

700.12 (F) Separate Service.
Where approved by the authority having jurisdiction as suitable for use as an emergency source of power, an additional service shall be permitted. This service shall be in accordance with the applicable provisions of Article 230 and the following additional requirements:
(1) Separate overhead service conductors, service drops, underground service conductors, or service laterals shall be installed.
(2) The service conductors for the separate service shall be installed sufficiently remote electrically and physically from any other service conductors to minimize the possibility of simultaneous interruption of supply.

I would not accept a MTM for that application based on listed item (2) as I don't see enough separation to keep a fault on one main from taking out both.