Health Care Facilities, and transfer switches per 517.30

[jfrog]

I have a situation that I've come across several times recently. I'm designing a small health care facility. The essential electrical system is less than 150 kVA, so per NEC 517.30(B)(2) I'm allowed to serve the essential electrical system with a single transfer switch. Since it's a small facility, all of the essential electrical system items are on a single panel.

The verbiage of NEC 2014 517.30(B)(2) is "One transfer switch and downstream distribution system shall be permitted to serve one or more branches in a facility with a maximum demand on the essential electrical system of 150 kVA."

Today an electrical plans reviewer told me even though I'm allowed to install a single transfer switch, the separate branches of the essential electrical need to be broken out into separate panels. My interpretation (as if that counts for anything :happysad is that this is part of the "downstream distribution" per 517.30(B)(2).

Does anybody here have any experience with this? I'd love to hear how this is being interpreted elsewhere.

 

[wsbeih]

I have a situation that I've come across several times recently. I'm designing a small health care facility. The essential electrical system is less than 150 kVA, so per NEC 517.30(B)(2) I'm allowed to serve the essential electrical system with a single transfer switch. Since it's a small facility, all of the essential electrical system items are on a single panel.

The verbiage of NEC 2014 517.30(B)(2) is "One transfer switch and downstream distribution system shall be permitted to serve one or more branches in a facility with a maximum demand on the essential electrical system of 150 kVA."

Today an electrical plans reviewer told me even though I'm allowed to install a single transfer switch, the separate branches of the essential electrical need to be broken out into separate panels. My interpretation (as if that counts for anything :happysad is that this is part of the "downstream distribution" per 517.30(B)(2).

Does anybody here have any experience with this? I'd love to hear how this is being interpreted elsewhere.

The way i interpret it is: it can be one main panel with many breakers to loads. However, this may not be practical if the panel location is in centralized location or if the loads are too many and require many circuit breakers for one panel to handle.
That's why what I typically see for such an application: at the load side of the single transfer switch you feed a main panel, out of which you distribute to few panels as needed. Simply no matter how you do it I'll call it downstream distribution.

 

[steve66]

I agree with the inspector.

The exception allows a single transfer switch. However, the code still requires separate systems (distribution) for the emergency and equipment branches.

 

[mikewright]

From my experience we have to separate life safety, critical patient, and critical equipment type loads. I.e. Exit lighting and blood bank refrigerators cannot exist off the same transfer switch, etc.


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