Exit sign logic

[Dex232]

Hello, I am looking for some help on understanding exit signs with emergency lighting on an emergency circuit. I am familiar with how battery powered exit signs with emergency lights function with no emergency circuit, they just run on battery power once main power is lost. But if I wanted to run an exit sign with emergency lights attached to main power and an emergency circuit so that the emergency lights turn on when main power is off but keep the emergency lights on when backup power is supplied is there a name for that behavior? I have heard the term "hot leg sensing" but could not find an exit sign that used this term to describe it.

Can any exit sign itself have this behavior or does it require outside logic with a relay?

I was looking to use Lithonia's LHQM series exit signs.

 

[d0nut]

That particular combo exit sign/emergency light has a battery in it. It isn't made to be fed from an emergency source like you are trying to do. If you have an emergency source, use the building lighting as your emergency lighting through a UL 924 or 1008 relay. There isn't a reason to use combo units or emergency unit equipment if you have an emergency source.

 

[Dex232]

That particular combo exit sign/emergency light has a battery in it. It isn't made to be fed from an emergency source like you are trying to do. If you have an emergency source, use the building lighting as your emergency lighting through a UL 924 or 1008 relay. There isn't a reason to use combo units or emergency unit equipment if you have an emergency source.

Thank you for the clarification.