Article 700.6 Transfer Equipment

[adalewhite]

(D) Use. Transfer equipment shall supply only emergency loads.

Does the paragraph above apply stricly to an emergency system that employs transfer equipment?

For instance it is clear that a system with both a computer room (optional) and emergency egress lighting served from a generator would require a transfer switch for each system. However, when you have a building and the entire facility is backed up by a generator would a transfer switch be required to isolate the legally required emergency systems?

700.5(B) seems to answer the question by allowing the alternate power source to supply emergency, legally required, and optional system loads " where automatic selective load pickup and load shedding is provided to ensure adequate power to (1) the emergency circuits, (2)the legally required standby circuits, and (3) the optional standby circuits, in that order of priority." There is also the requirement for a temporary generator whenever the emergency generator is out of service.

So let's say we have a facility where the existing emergency lighting is battery ballast without a separate emergency circuit. The client desires the entire facility to be backed up with a new genset. We know from experience the maintenance of the battery ballast will no longer take place since the generator is picking up the entire facility. With that in mind do I now also have to design the new system to provide separate circuits to provide the required level of emergency lighting and power?

 

[Nick]

Re: Article 700.6 Transfer Equipment

I have done several installations where the entire facility is backed up with the generator. The transfer switch was considered an article 702 optional stand by system and the required article 700 emergency loads were handled with battery back up. (lights and exit signs)You could design an emergency system utilizing a separate transfer switch and distribution but it would be a whole lot cheaper to maintain the existing battery ballasts.

 

[steve66]

Re: Article 700.6 Transfer Equipment

I agree with Nick, it would probably be cheaper for your client to maintain the battery packs than to install another transfer switch and connect it to all the emergency lights. This has the added benefit that they don't need to get a temp. generator when the other one is out of service. Then Article 700 wouldn't apply to the generator.

If your client does decide he isn't going to maintain the batteries, he does need two transfer switches. If he says he will maintain the batteries, and he doesn't, that's not your problem.

Steve

 

[adalewhite]

Re: Article 700.6 Transfer Equipment

Thanks for the feedback. Here's the scoop.

If a facility's emergency system is battery powered emergency lighting, exit signs etc and a generator is installed to power the entire facility the existing battery powered emergency system is still intact and would still fall under the requirements of NFPA 101, 7.9 for testing and maintenance. No transfer switch is required for the emergency system.

If the owner did not want to maintain or continue to use the battery powered system then an emergency system complying with NEC 700 would have to be installed.

If the facility had an existing generator powered emergency system and transfer switch and generator/s are installed to backup the entire facility then NEC 700.5(A)&(B) apply and the exsiting emergency system has to be worked into the arrangement so that less critical loads are shed as required to maintain power to the emergency system. Additionally provisions must be made for a temporary generator during maintenance periods lasting longer than a few hours.