Modular building at hospital.

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storeytime

storeytime

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I've searched the code and the forum; I'm not sure about this, so here goes.
3 section modular building is being moved in next to hospital. Feeding the modular with a 400A and a 200 amp circuit from the hospital distribution panel which is 3 PH, 208V. Feed will be thru EMT across roof to gutter on top of modular. <continuous metal path between buildings> (200 - 2" C, 3/0's ; 400 - {2} 2" C, parallel 3/0's). This powers all of the lighting and 120V power in the modular. Each feed goes straight to main breakers on the respective load centers in the modular.

The Catscan and MRI are each fed seperately from seperate services not located in hospital building. Services are pole mounted about 200' away.
MRI - 480V, 3PH, 200A, PVC UG, 3/0, 5 wire.
CTscan - 480V, 3PH, 150A, PVC UG, 2/0, 5 wire.
Each 480 feed goes straight in the bottom of the modular to the main breaker on the equipment.

I'm confused about the grounding requirements; ground rods at modular for each feed? bonding? I can use all the help I can get.
 
Storytime

You should check 225.30. The general rule is that you can have only one set of feeder conductors to a building. Additionally if you get by that rule, you seem to be in trouble with 225.32 because disconnects aren't grouped.

Jim T
 
One set of feeder conductors

One set of feeder conductors

jtester said:
Storytime

You should check 225.30. The general rule is that you can have only one set of feeder conductors to a building. Additionally if you get by that rule, you seem to be in trouble with 225.32 because disconnects aren't grouped.

Jim T
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Thanks for the reply Jim. I guess this is up for interpretation but I believe that 225.30 (B) (2) and (D) might give me the OK. (B) (2) says "A single building or other structure sufficiently large to make two or more supplies necessary."

-And- (D) says "Additional feeders, or branch circuits shall be permitted for different voltages, frequencies, or phases or for different uses, such as control of outside lighting from multiple locations."
The modular building is 7344 square feet. It is assembled in 3 sections on site.
The 400 amp load center in the modular is in the middle section. The 200 amp load center is in the same equipment room as the 400 amp. (These are 208V)
The 480V equipment is in another section of the modular.
The hospital building has no 480V power. We are using two 480V services that we installed for (1) A 480V MRI trailer and (2) A 480V Catscan trailer. Both of these temporary trailers are going to be replaced by the equipment in the modular. These services feed to the trailers underground. We were planning on taking the 200A, 480V straight to the MRI equipment main breaker and taking the 150A, 480V straight to the Catscan equipment main breaker. All of the 120/208 power has to come from the existing distribution panel in the hospital main equipment room. I don't see any realistic way that we can power the modualar any other way or how we can group disconnects together because of logistical problems. I'm wondering if 235.32 Exception No. 1 gets me around the location for disconnection problems. The hospital has a maintenance staff and has established procedures in place. Example: The main disconnecting means for all of the 208 power to the hospital is in an equipment room that has a locked door. It is all fed from a locked utility company transformer. So there is no way in the existing setup to kill the power during a fire without going through maintenance or utility company, which I believe is the purpose for disconnecting means being located together and outside the premises. But, I'm open to suggestions. I certainly am not the most knowledgeable person on this situation.
 
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I'm not sure why it is difficult to provide a single 480 volt feed, and transform the 208 down. Or if you use 225.30 D you could have a single 480 volt feeder and a single 208 volt feeder with disconnects at one location and then feed each modular and piece of equipment from there.

I've done a number of designs like this and I often call for a single feeder into a main lug panel with a breaker for each modular section.

Jim T
 
It seems to me you can't feed it with more than one circuit just because it is convenient to do otherwise. OTOH, is the modular building attached physically to the existing structure in some way? Maybe it is not really a detached structure.
 
The modular will be attached by a canopy over the walk for about 2/3 of the adjoining side. I don't know if that qualifies it as seperate building or not.

Transforming the 480 to 208. We don't have enough amperage on the 480 services to serve the 480 and the 208. One service is a 200 amp. The other is a 150 amp. The load requirements for the modular are 260A, 199A, and 110A on the 208V loads and 200A, 150A on the 480V.

Naturally the hospital wants to utilize whatever power they already have in place, so they want to avoid more transformer changes from the utility company, re-trenching over 200' through parking lot, new conduit & wire. So, we're trying to provide them with what they need while utilizing some of what they already have. I'm seeing these exceptions that I mentioned giving us some flexibility in giving them that option. Does anybody see that I'm mis-applying these exceptions?
 
There are issues in your setup that only your local inspector can answer. I believe you should call him and send him a diagram of what you are trying to install. In the diagram give distances and other specifics that will help him to properly figure this out. Remember that hospitals also have other AHJ types, such as JACHO (I think that is it), that they must satisfy. It could become a very costly mistake if you should choose not to.

I also would be inclined towards leaning to what jtester had to say in his posts.
Also, you may be able to get the buiding department to say it is one building...have something structural built between the two structures.
 
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