Generator backing up whole building

[Machiavelli999]

I work for a major corporation with a large multi-building manufacturing campus. When I started here, one of the first thing I noticed is that multiple critical buildings on the campus have generators tying into the main service switchboard. This struck me as odd because I always thought the code required segregation of Article 700 loads from other loads. Yet, when I brought up the code requirement, all I got was blank stares. No one had a clue. In fact, I was told switchgear manufacturers specifically make transfer switch control logic at the switchboard level so you would not need a stand alone ATS. Our switchboards have these controllers built-in to handle transfer logic: http://www.precisioncontrols.co.uk/assets/downloads/woodward-lr/gcp-30-series-user-manual.pdf

Another switchboard on our campus, that also has a generator tied into it, has an elaborate GUI showing status of generator, switchboard, and status of all breakers. All of these installations have been permitted.

Anyway, I let this go and stopped raising any objection. Obviously I wasn't going to make them rebuild the entire electrical infrastructure on campus. But this is coming up again as another building service switchboard is due for replacement and the request came to tie the generator into this switchboard upon replacement. How do I justify this as legal though? What am I missing?

 

[tom baker]

Ade these legally required standby sysyems, as required by the AHJ?

 

[Machiavelli999]

Ade these legally required standby sysyems, as required by the AHJ?

You mean the building itself? It's a pharma manufacturing building, but no I don't believe it's an Article 701 load. But even if it was, is there not a requirement to keep it segregated from Article 700 loads?

 

[Machiavelli999]

Here is an extensive article describing power transfer systems for switchboard where generators tie in:

Automatic transfer system explained in detail (operational requirements) | EEP

Operational requirements of automatic transfer system include initiation of transfer, dead-bus considerations, generator starting, completion of transfer,

electrical-engineering-portal.com

Including the following graphic:



This is very similar to what we have. But again, how is this legal per code?

 

[tom baker]

First, who classified the system as Article 700 loads?

 

[texie]

You mean the building itself? It's a pharma manufacturing building, but no I don't believe it's an Article 701 load. But even if it was, is there not a requirement to keep it segregated from Article 700 loads?

The same genset can be used to supply 700, 701 and 702 loads. The 700 loads would need to be on a separate ATS along with separate raceways for the 700 loads.

 

[Machiavelli999]

The same genset can be used to supply 700, 701 and 702 loads. The 700 loads would need to be on a separate ATS along with separate raceways for the 700 loads.

But that's what I mean. It's not. In fact, there are no standalone transfer switches. Transfer control is done by a PLC integral to the main service switchboard.

 

[tom baker]

You have the gist, if any loads are classified as Art 700, emergency, then that wiring is to be kept separate, as pointed out.
You asked if its legal, no if its truly an Art 700 system
I am asking who determined this is an Art 700 system. Please see definition of Emergency Systems and the IN.
The reason I ask is its common for someone who doesn't' understand the NEC to call a generator system an emergency generator when its typically an Art 701 or 702 system.

 

[Machiavelli999]

You have the gist, if any loads are classified as Art 700, emergency, then that wiring is to be kept separate, as pointed out.
You asked if its legal, no if its truly an Art 700 system
I am asking who determined this is an Art 700 system. Please see definition of Emergency Systems and the IN.
The reason I ask is its common for someone who doesn't' understand the NEC to call a generator system an emergency generator when its typically an Art 701 or 702 system.

It is my understanding, perhaps wrongly, that all egress lighting loads (as an example) are Article 700 loads. At the very least, I know the building has egress lighting.

 

[GoldDigger]

It is my understanding, perhaps wrongly, that all egress lighting loads (as an example) are Article 700 loads. At the very least, I know the building has egress lighting.

Many buildings use an entirely separate battery backup system for egress lighting, removing any possible need for Article 700 loads on the generator.
If the generator is only needed to supply lighting for longer periods than the mandated egress time period, that does not make the generator part of the legally required egress lighting system.

 

[PE (always learning)]

It is my understanding, perhaps wrongly, that all egress lighting loads (as an example) are Article 700 loads. At the very least, I know the building has egress lighting.

Are the egress lights on battery backup or do you know they are fed by the generator for a fact? If they are indeed battery backup then your generator may not be feeding life safety loads. I agree with the other statements, who determined this as an Article 700 system?

 

[hillbilly1]

Are the egress lights on battery backup or do you know they are fed by the generator for a fact? If they are indeed battery backup then your generator may not be feeding life safety loads. I agree with the other statements, who determined this as an Article 700 system?

If it is an existing building, they should already have independent battery backup. Those still have to be maintained after the generator is added.

 

[tom baker]

I think you have a 701 or 702 generator.
Look at the definition of Emergency Systems and the IN in Article 700, I have clipped it here. If an AHJ hasn't told your company its a Emergency System, or its legally required, then its not an emergency system