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Horse piddle #80909 06/10/02 06:07 PM
Joined: Jan 2002
Posts: 64
Rabbit Offline OP
Am coming out of the main switch gear in a hospital with a 480v 150a feed. The gear is in the basement. This will feed a new 208/120 panel on the 3rd floor via a transformer, also on the 3rd floor. The print shows the feeder going strait to the trans. Don't I need a disconnect here? Panel is main brkr. Also this panel will serve some isolated ground circuits. Does the ig have to go all the way back to the gear or can it stop at the trans? Articals?

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Re: Horse piddle #80910 06/10/02 06:36 PM
Joined: Nov 2000
Posts: 2,148
resqcapt19 Offline
There is not a code requirement to have a disconnect at the transformer. The transformer primary does require an OCPD, but that can be at the main gear and provide the required protection for both the feeder conductors and the primary side of the transformer. As for your isolated grounds look at 250.146(D). They must trerminate at a point where they can clear any ground fault. For your SDS, that would be at the same point where you connect the grounding electrode conductor for the secondary of the transformer.

[This message has been edited by resqcapt19 (edited 06-10-2002).]

Re: Horse piddle #80911 06/10/02 08:39 PM
Joined: Sep 2001
Posts: 25
dlabrenz Offline
I would think that a disconnect would be required to protect the secondary conductors.
240-21(c)(1) seems to indicate that the secondary conductors are not protected by the primary OCPD, and I am not sure that I would like unprotected conductors running 3 floor til they get to the mail in the load center.

Re: Horse piddle #80912 06/10/02 09:39 PM
Joined: Jan 2002
Posts: 64
Rabbit Offline OP
Thanks Don. This is my first hospital and it just didn,t look right. I will proceed.
Dlabrenz, the conductors are protected at the switch gear, approx. 150 ft.

Re: Horse piddle #80913 06/10/02 10:39 PM
Joined: Nov 2000
Posts: 2,148
resqcapt19 Offline
The main in the panel can provide the required protection of the secondary side of the transformer and the secondary conductors. This may involve the use of the "tap" rules that will limit the length of the secondary conductors.



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