Inverter Emergency lighting

[Moore Power]

I am bidding on a dialysis clinic that has owner supplied light fixtures and an inverter. The plans call for 2 inverter circuits throughout the facility, the inverter is not fed from the same circuits that will feed the general lighting. Am I correct in assuming that this is not an issue because 700.12 H only applies to Battery back up? I've never thought about it before but this has me scratching my head because the entire tenant space is on an optional generator also.

 

[d0nut]

You will need UL 924 or UL 1008 listed relays, depending if there is both normal and emergency egress lighting in a space, to sense power loss in that space and force the emergency egress lighting on. The optional standby generator has nothing to do with the emergency egress lighting (hence the inverter) other than those lights can go back to being controlled with the normal lights when power to the facility is restored through the generator.

Make sure that generator is really an Article 702 Optional Standby generator and not an Article 517 Essential Electrical System generator.

 

[Moore Power]

Thank you. They are supplying UL 294 relays maybe a typo. My main question has to with emergency lighting being on the same circuit as the general area lighting. Does this only apply to battery back up EM lighting?

 

[d0nut]

Kind of. The emergency egress lighting is required to turn on when the normal lighting in a space is lost, not just in a utility outage. With unit equipment or luminaire mounted batteries, it is trivial to use the battery charging circuit as the sensing circuit so that is how the equipment is built. When there is no voltage on the battery charging circuit, the equipment knows normal power is lost and turns on.

Since the inverter output feeds multiple areas with multiple normal circuits feeding the normal lighting, this same approach won't work. If you sense only the input circuit, you would know if there was a utility outage or if the input circuit lost power, but you wouldn't know if one of the normal lighting circuits had lost power which could leave an area in darkness. The UL 924 or 1008 relays move the power loss sensing to the individual normal lighting circuits to allow the emergency egress lights to turn on if that normal circuit loses power. Your inverter typically doesn't get fed from the same circuits feeding the normal lighting because there are typically multiple circuits. A relay gets provided for each normal lighting circuit, and usually each control zone if you want the emergency egress lighting to follow the normal lighting switching, that will have a voltage sensing circuit to force the emergency egress lighting on upon loss of the normal lighting circuit in the area.

The output of an inverter gets wired similarly to emergency egress lighting fed from a generator.

 

[Moore Power]

Kind of. The emergency egress lighting is required to turn on when the normal lighting in a space is lost, not just in a utility outage. With unit equipment or luminaire mounted batteries, it is trivial to use the battery charging circuit as the sensing circuit so that is how the equipment is built. When there is no voltage on the battery charging circuit, the equipment knows normal power is lost and turns on.

Since the inverter output feeds multiple areas with multiple normal circuits feeding the normal lighting, this same approach won't work. If you sense only the input circuit, you would know if there was a utility outage or if the input circuit lost power, but you wouldn't know if one of the normal lighting circuits had lost power which could leave an area in darkness. The UL 924 or 1008 relays move the power loss sensing to the individual normal lighting circuits to allow the emergency egress lights to turn on if that normal circuit loses power. Your inverter typically doesn't get fed from the same circuits feeding the normal lighting because there are typically multiple circuits. A relay gets provided for each normal lighting circuit, and usually each control zone if you want the emergency egress lighting to follow the normal lighting switching, that will have a voltage sensing circuit to force the emergency egress lighting on upon loss of the normal lighting circuit in the area.

The output of an inverter gets wired similarly to emergency egress lighting fed from a generator.

That was very helpful, Thank you.