Fire Pump in Existing Building

[SparkyJ]

We are replacing the fire pumps and generator in an existing building.

Current system was put in circa 1973 and is NOT up to current code. The service disconnecting means is an MCC and the feed to the 50hp fire pump is a 100A breaker in an MCC bucket.

The service entrance conductors come in from the utility transformer to underneath the MCC. Fire pump contractor is installing nice new controller/ATS and we have to feed it. The problem I have is there is no way to tap the service entrance conductors before the main breaker without doing it in the bottom of the MCC. I should mention that the service rated MCC, fire pump controllers, and fire pumps are all located in the same room.

I understand from my extensive research in Article 695 (begun today) that the Service Conductors 695.6(A) can only be routed through the building if they meet the requirements of 230.6(1) or (2). This requires them to be encased in 2? of concrete. For a while I thought that the exception after 695.6(B) would save me, but that only applies to the conductors from the last OCPD to the pumps. Right?

My plan of attack right now is to intercept the service entrance conductors underneath the MCC and make a tap to the fire pump controller (service rated, locked rotor size breaker, etc?). I plan on installing the conduit on the floor and forming up 2? of concrete around it. The building is going to be torn down in 4 years anyway. The problem I have is how to size the tap conductors. The tap rules in 240.21 do not apply to service conductors according to the definition in 240.2. I need #4 conductors according to the FLA of the motors. Can I just use that? Do the tap rules apply? Do I have to use MI or fire rated cable?

 

[RUWired]

For a while I thought that the exception after 695.6(B) would save me, but that only applies to the conductors from the last OCPD to the pumps. Right?

I plan on installing the conduit on the floor and forming up 2? of concrete around it. The problem I have is how to size the tap conductors. The tap rules in 240.21 do not apply to service conductors according to the definition in 240.2. I need #4 conductors according to the FLA of the motors. Can I just use that? Do the tap rules apply? Do I have to use MI or fire rated cable?

The conduit as you describe on the floor with the 2" of concrete has been approved before and should not be a problem. The exception to 695.6(B) is only where they stub up or down into the enclosure.
The tap conductors are service conductors and fall under 230.46. Minimum sizes are located in 230.42 for service conductors and 250.24(C) for the grounded conductor requirement.
Rick

 

[hillbilly1]

If I remember correctly, you can tap in the MCC where the service conductors come in as long as the MCC main is not in the same enclosure, such as a pull section before the main. From there you still have to have the 2 hour fire rating, I usually just go out the back, and run on the outside of the building, that way a 2 hour firewall will only be needed once it re-enters the building, but since everything is in the same room, I think your on the right track with the concrete cover.