Single Generator Multiple Buildings

[dcrwly10]

I am working on a project where we have a single generator that will serve multiple buildings on a college campus. These buildings are all new construction. Currently the generator only serves a single building's life safety loads and central plant equipment. The generator was designed with a spare breaker for connection to a future building. The generator feeds (2) 3-pole automatic transfer switches. It was recently brought to my attention that this may be a code violation and 4-pole transfer switches may be required. Can anyone reference the code section that this would be in violation of? And if so, is there a solution where the 3-pole ATS's can remain in place?

 

[mgookin]

Is each building fed by a separate xfrmr?

Can you get a bit more descriptive as to what voltages/ phases you have and what your service entrance conductors are for each?

 

[dcrwly10]

Yes, each building is fed by a separate transformer. The issue I see is that there is the potential for one building to loose power and call for the emergency generator to fire and feed the ATS with emergency power while another building still has normal power. Without the 4-pole transformer, there is no way to isolate the neutral from one serve to the other. Correct?

Voltage is 480V-3ph. Three separate services, 3000A, 2000A & the third is yet to be determined.

Is each building fed by a separate xfrmr?

Can you get a bit more descriptive as to what voltages/ phases you have and what your service entrance conductors are for each?

 

[kingpb]

Since you listed the voltage as 480V 3ph, The assumption is that you don't actually need the neutral for loads. is this correct?

Another assumption; the generator is not big enough to handle more than one building at a time and the ATS's are configured to block transfer if the generator is running and feeding one building the other two won't transfer.

Are either of these correct?

 

[dcrwly10]

No the generator is sized to carry on the life safety loads for each building so if 1 or both of the building lose power the generator will have to fire. And the service for each building is 480/277V-3ph, 4W so it does need the neutral.

Since you listed the voltage as 480V 3ph, The assumption is that you don't actually need the neutral for loads. is this correct?

Another assumption; the generator is not big enough to handle more than one building at a time and the ATS's are configured to block transfer if the generator is running and feeding one building the other two won't transfer.

Are either of these correct?

 

[Some Dude In Dallas]

I am not aware of a code requiring the use of a 4-pole ATS. However, using both 3-pole and 4-pole ATS on the same system would be a violation. You would not be able to provide a proper grounding system for both types on the same generator; check out 250.30.

Sound like you may also be in violation by mixing article 700 (life safety) and 703 (optional standby-'central plant') systems.

 

[texie]

I am working on a project where we have a single generator that will serve multiple buildings on a college campus. These buildings are all new construction. Currently the generator only serves a single building's life safety loads and central plant equipment. The generator was designed with a spare breaker for connection to a future building. The generator feeds (2) 3-pole automatic transfer switches. It was recently brought to my attention that this may be a code violation and 4-pole transfer switches may be required. Can anyone reference the code section that this would be in violation of? And if so, is there a solution where the 3-pole ATS's can remain in place?

If I understand you correctly you have building X with a service and a genset with a 3 pole ATS. Now you want to feed buildings Y and Z with the same genset that each have their own service.
At first blush, as this will need further vetting, I would think you could leave building X as is with the 3 pole ATS and use 4 pole ATS's at building Y and Z. This way you will not be tying the neutrals of each building service together downstream of the service main.
I'm assuming you will have an EGC in the emerg. feeder to each building and you will bond that to building Y and Z's GES respectively as per Art. 225 rules.