two connected buildings, two services, transfer switch questions

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olc

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This question is about grounding and bonding only with all other electrical issues (are there are some) aside.
Two connected buildings each with their own service. One is a hospital and the other is an apartment building. There is a fire wall. Sometime in the 70?s (this is when the apartment building was renovated for apartments) a transfer switch was installed in the apartment building to serve an elevator and emergency lighting. It is normally connected to the apartment building service. The standby side is connected to a feeder which is connected to a distribution panelboard in the hospital which in turn is connected to a transfer switch in the hospital. So the apartment building transfer switch standby side feeder is live.
The neutrals are all connected in the apartment transfer switch.

1. Should the standby side neutral (from the hospital) not be connected to the apartment neutral?
The way to do this is a 4 pole transfer switch? (It is currently a 3 pole transfer switch.)

Maybe when they installed it they considered it one building because there is no disconnect on the standby feeder where it enters the apartment building (the disconnect is the circuit breaker in the hospital panelboard).
2. If we say it is two buildings and add a disconnect on this feeder at the wall of the apartment building (calling is a service entrance ? emergency/standby whatever) should the neutral be bonded to a ground at that point?
 
I think the answer may hinge on whether the services' GES or EGS share anything other than earth. If they do, you have parallel grounded conductor current on the grounding systems if the transfer does not switch the grounded conductor.
 
The EGC (ground conductor) for the standby feeder from the hospital is connected to the EGC of the regular power at the case of the transfer switch. Also the standby feeder is in metallic conduit. So yes.
 
olc said:
The EGC (ground conductor) for the standby feeder from the hospital is connected to the EGC of the regular power at the case of the transfer switch. Also the standby feeder is in metallic conduit. So yes.
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And with the grounded conductor not switched, they have a parallel pathway for grounded conductor currents of both services. I'd say a 4-pole transfer switch is required.

As to a disconnect being required at the sparating wall, that'll depend on whether the structure is considered one building or two under local building code interpretation. Not my area to even make a guess.
 
IF we put in a disconnect at the standby service entrance should the neutral be connected to the ground. My feeling is no because that will essentially be the same as connecting the two service neutrals.

I agree that the transfer switch should be 4 pole.
 
olc said:
IF we put in a disconnect at the standby service entrance should the neutral be connected to the ground. My feeling is no because that will essentially be the same as connecting the two service neutrals.

I agree that the transfer switch should be 4 pole.
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The neutral to ground bond should already exist elsewhere, so do not connect neutral to ground at the standby disconnect.
 
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