NFPA 72 Backup Power requirements

[nhee2]

This question is more NFPA 72/110 than NEC but I will ask here anyway.

NFPA 72 allows battery backup to be sized for 4 hours if the secondary power supply (generator) meets NFPA 110 requirements for a type 10, Class 24, Level 1 system.

Although the section only mentions the generator, is it correct that the distribution between the generator and FACP needs to be designed as emergency power? Site we are working at has generators that would meet the NFPA 110 requirement but there is no segregation of 700/701/702 loads. (all are 702 I guess). I am assuming I need 24 hour battery for our FACP, but want to make sure I understand correctly.

 

[JoeStillman]

This is one of those situations where it hurts to follow the code. Hurts because you know darned well it'll be fine, and you're going to have to defend the decision to go to more expense just because the code says so.

Follow the code. If reliability is good, more reliability is better.

 

[ron]

Type 10 indicates the generator must start and restore power in 10 seconds, like an Article 700 generator.

Level 1 systems provide power where failure would result in “loss of human life or serious injuries”, again like Article 700.

NFPA 72 section that refers to the Secondary power supply indicates "an automatic-starting, engine-driven generator serving the branch circuit" must have those qualities, so it must be a 700 generator and the pathway all the way down to the branch circuit. section 10.6.7.3.1(2) from the 2013 version which I have handy

So you will be stuck with 24 hours of battery.

 

[nhee2]

thanks for the replies.

That is how I read it also. Although I've seen systems which credited the generator when the generator met the requirements, but the downstream distribution did not.

I agree in my case 24 hr is required.