Separation of ATS Feeders for a hospital (more than 150KVA)

[steve66]

Using the 2014 NEC.

Does 517.30(F) allow me to run a single feeder as shown in the second diagram of the attached PDF?

Or does 517.30(F) only apply to a feeder directly connected to the alternate source?

517.30(F): Feeder from Alternate Source Power: A single feeder supplied by a local or remote alternate source shall be permitted to supply the essential electrical system to the point at which the life safety, critical, and equipment branches are separated. Installation of the transfer equipment shall be permitted at other than the location of the alternate power source.


517.30(C) basically says the critical branches have to be kept separate from other branches. But I'm not sure if this also applies to the emergency feeder to the ATS, or if it only applies to the wiring after the ATS. At one time, the ATS was the point where all the wiring had to start being separated, but with all the code changes to emergency systems, I'm not sure if this is true anymore.

If (C) only applies to the wiring after the ATS, then I don't know why 517.30(F) would even be needed. Because if there isn't any code requirement to keep the ATS feeders separate, then we wouldn't need a paragraph to tell us that we can use a single feeder.

View attachment ATS Feeders.pdf

 

[packersparky]

I think a single feeder is allowed to the point where the systems are separated. That would also be consistent with 700.10(B)(5)(d).

517 in the 2017 NEC was extensively revised. This little blurb was added in 517.31, and seems to support a single feeder.


The division between the branches shall occur at transfer
switches where more than one transfer switch is required
[99:6.4.2.2.1.2]

 

[steve66]

I think a single feeder is allowed to the point where the systems are separated. That would also be consistent with 700.10(B)(5)(d).

517 in the 2017 NEC was extensively revised. This little blurb was added in 517.31, and seems to support a single feeder.


The division between the branches shall occur at transfer
switches where more than one transfer switch is required
[99:6.4.2.2.1.2]

Thank you. I was a little concerned that the "alternate source" mentioned in 517.31 would not include a panel or switchboard downstream of the generator itself.

But the 99 quote seems to say I can run a single feeder from a panel, and divide the branches farther downstream.

 

[Russs57]

What I have seen recently done at my hospital.....run single generator feeder to "essential power panel". Feed emergency side of life safety, critical, and equipment ATS's from this panel.

So I would say yes, in my area, as I understand your question. Codes are generally tougher here due to hurricanes.