Life Safety and Critical Care circuit separation

[ncwirenut]

Plan review has turned us down because we have set a panel beside of the generator to distribute the generator power at a nursing home. They say we cannot share the Life Safety and the Critical Care power after it leaves the generator. This is a new building with one Life Safety ATS and three Critical Care ATS. Their recomendation is to set a trough inside of the generator and tap these panels in the trough. I'm probably wrong but I never thought that the seperation applied before the transfer switch. Any thoughts?

 

[roger]

See the FPN Figures 517.41 #1 and #2

Roger

 

[charlie b]

I have had a similar situation. The plan reviewer's concern was that the generator had a circuit breaker of its own, and the separation into different groups happened after that point. We removed the generator breaker, and the plan reviewer approved the design.

 

[Chris3585]

I'm not sure I understand the difference whether the overcurrent protection devices are within the generator enclosure or in a panel outside of the enclosure. It is my understanding the the division between the systems happens after the automatic transfer switches, not before. Have you reviewed NFPA 99, chapter 3 or NFPA 110 to help determine what defines the start of the branches?

I have fed multiple ATS in the past (critical branch, life safety, equipment branch) from a panel fed by a transformer and not had an issue with inspections.

Chris

 

[roger]

Chris, see page 47 of this document to see what NC wants

Roger

 

[Chris3585]

Roger,

That is interesting, but does it have basis in code or is the seperation just required for State of NC owned projects. I don't have my NFPA 99/110 with me right now or I would research.

Chris

 

[roger]

Chris, the NC illustrations are basically the same illustrations shown under 700.9(B) of the NECH.

Roger

 

[charlie b]

I'm not sure I understand the difference whether the overcurrent protection devices are within the generator enclosure or in a panel outside of the enclosure.

In my case, the problem was having both. The plan reviewer's take on the requirements was that the separation rules applied as soon as you cross the first overcurrent device or the first ATS. So if there is a generator breaker, and you have a single feeder going from there to a panel, and you plan to serve both emergency and non-emergency loads from the panel, then you have violated the separation requirements. The feeder from the generator breaker to the panel has both types of loads.

So I was essentially posing the question of whether the installation under discussion includes a generator breaker upstream of the panel.

 

[steve66]

Chris, the NC illustrations are basically the same illustrations shown under 700.9(B) of the NECH.

Roger

Roger:

Maybe the 2011 is different, but in the 2008 Handbook, illustration 700.3 specifically shows a single main breaker is OK as long as it is selectively coordinated (700.9(5)(b) exception).

Also, since both the Critial Branch and the Life Safety Branches are part of the emergency system, aren't they both Article 700 loads? So I'm not sure the illustrations in Article 700 apply the same as they would to an emergency load and a non-emergency load.

Steve

 

[skeshesh]

In my case, the problem was having both. The plan reviewer's take on the requirements was that the separation rules applied as soon as you cross the first overcurrent device or the first ATS. So if there is a generator breaker, and you have a single feeder going from there to a panel, and you plan to serve both emergency and non-emergency loads from the panel, then you have violated the separation requirements. The feeder from the generator breaker to the panel has both types of loads.

Was the sole purpose of above mentioned breaker protecting the conductors from the generator to the distribution? And are you saying that you there was no main breaker used in the distribution board? How was the feeder overcurrent protection accomplished?

 

[roger]

Roger:

Maybe the 2011 is different, but in the 2008 Handbook, illustration 700.3 specifically shows a single main breaker is OK as long as it is selectively coordinated (700.9(5)(b) exception).

Steve, illustration 700.3 is showing a single main breaker, but it is the main for a three vertical section panel board where each system is separated before the ATS's.

Roger

 

[charlie b]

Was the sole purpose of above mentioned breaker protecting the conductors from the generator to the distribution? And are you saying that you there was no main breaker used in the distribution board? How was the feeder overcurrent protection accomplished?

The distribution did not have a main breaker. The feeder from the generator to the distribution board was protected by the combination of the two (or it might have been three, I no longer recall, as this was several years ago) breakers on the distribution board.

 

[ncwirenut]

To answer a question, the generator has one breaker, the panel beside of the generator is a MLO with four breakers for the four ATS. I may be violating the code, but it seems to be a better installation than using a trough.

 

[skeshesh]

The feeder from the generator to the distribution board was protected by the combination of the two (or it might have been three, I no longer recall, as this was several years ago) breakers on the distribution board.

I'm sorry I don't exactly understand what you mean by "protected by the combination of x#of breakers". It's probably something that's not clicking in my head right now but I'd really appreciate a bit more explanation.

 

[ncwirenut]

A common installation in nursing homes with under 150kva essential electrical system demand is a breaker on the generator feeding one ATS that feeds one panel that feeds the life safety panels and the critical care panels. I can feed multiple panels from the ATS, but the feed to the generator is still feeding both. 517.41 clearly states that is acceptable. Are you saying that the seperation does not apply here?