Min. 2 ATS per building?

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anbm

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Medical office building, if we have emergency generator, do we require to have minimum (2) ATS?

One ATS only serves egress lights, fire pump and fire alam control only (legally required emergency system).

The remain ATS can serve other emergency load as required by the owner? (elevator, pump, exam room outlets, etc)
(optional)

I was thinking this belongs to NEC 700 or building code but couldn't locate exact section at this time,
anyone know?
 
Yes, the life safety has to be on a separate transfer switch, unless........ It has a separate power source that's not dependent on the generator for backup. Fire pump will have it's own transfer switch, so you may end up with three transfer switches.
 
anbm said:
Medical office building, if we have emergency generator, do we require to have minimum (2) ATS?

One ATS only serves egress lights, fire pump and fire alam control only (legally required emergency system).

The remain ATS can serve other emergency load as required by the owner? (elevator, pump, exam room outlets, etc)
(optional)

I was thinking this belongs to NEC 700 or building code but couldn't locate exact section at this time,
anyone know?
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Can't answer with certainty because you are saying it is a medical office building. Not an expert in this area, but I feel under the NEC, there is no such building type. It is either a health care facility, or it is not.

Additionally, there is no such thing as owner-required emergency loads. See 700.1 Scope for the "who decides"... and owner is not one of them.
 
A medical office buliding is still under the requirements of article 517. Technically, your facility has an Essential Electrical system described as (3) distinct branches: Life Safety, Critical Branch and Equipment Branch.

However, I will typically still use (2) ATS's in a medical office building, one defined as the life safety branch, that will serve typical Article 700 Emergency Loads.

The other ATS is defined as the Equipment Branch and is suitable for your typical optional standby loads.

When looking at the requirements for a critical branch, most medical office buildings will not have "Critical Care Areas" or loads that require a critical branch circuit. Therefore, a critical branch is often not necessary and may be omitted from this application.

This has been my interpretation, and I've not had issue with this interpretation in the past.

An MOB falls under 517.45 "Other Healthcare Facilities" and does allow for battery systems to serve the "Essential" Electrical system, which is most-likely just load categorized as Life Safety (exit and egress lights, fire alarm, etc..)
 
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One other point. The fire pump stated in your post, I do not believe is acceptable on the Life Safety branch, as the branch is reserved exclusively for those loads described in 517.32.

My preference is a separate service-entrance rated transfer switch/controller for the fire pump.
 
hillbilly1 said:
Yes, the life safety has to be on a separate transfer switch, unless........ It has a separate power source that's not dependent on the generator for backup. Fire pump will have it's own transfer switch, so you may end up with three transfer switches.
Click to expand...

I agree with this. Three ATSs (fire pump has its own ats). Medical office building is class B occupancy and won't fall under 517.
 
anbm is correct i am working on a medical office building right now and it has no generators only battery back-up on certian lights, F.A. system, security and some E.B.U. lights thats it. I dont believe it falls under the clasification of a health care facility. as no patients go there nor are there any procedures performed there. it is classified as just a regular office building...
 
I have to disagree that a medical office building is not considered a healthcare facility.

A medical office building is classified as an "Other Healthcare Facility" per 517.45.

Also, see 517.25 Scope for inclusing of medical office buildings in the description.

You will also need to follow all other requirements for healthcare facilities as outlined in 517 such as redundant grounding in areas administering patient care.
 
copper chopper said:
anbm is correct i am working on a medical office building right now and it has no generators only battery back-up on certian lights, F.A. system, security and some E.B.U. lights thats it. I dont believe it falls under the clasification of a health care facility. as no patients go there nor are there any procedures performed there. it is classified as just a regular office building...
Click to expand...

The facility does not require a generator because this is allowable under 517.45, however this does not mean it is not a health care facility as defined by the NEC.
 
If the demand is 150KVA or less, then the LS branch and Critical branc can come from the same Automatic transfer switch.

My understanding is that separate distribution systems are still needed. So a single ATS could supply a LS panelboard and a critical panelboard.
 
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