Adding UPS to critical branch and equipment branch in between while power sources switch

[hhsting]

Please see below riser. I have two existing incoming electric utility services coming into two separate existing substation switchgear 480/277V three phase inside hospital. There are existing ATSs critical and equipment branches which feed downstream panelboards shown by dotted line existing cables to be removed. The dotted lines are cables that will be removed and solid cables will be the new connection. Now they want to place UPS between ATS and the existing downstream panelboard. This is to fill the gap time meanwhile downstream ATS switch. So, in some cases, they placed 1200A panelboard E2-DP-1, E2-DP-2 and downstream of that they placed 300kVA UPS and in some cases, they just place the 300kVA UPS without the panelboard. The UPS runtime is 6 minutes. Panelboards E2-DP-1 and E2-DP-2 feeder breaker is 600A feeding the UPS-CR-1, UPS-CR-2.

Below the Riser are three types of UPS used in the riser. UPS-RAD has internal 500VA 120V to 480V transformer in Maintenance bypass panel and separate 300kVA 480V delta to 480/277V transformer cabinet. UPS -CR-1 and UPS-CR-2 has 500VA 480V delta to 120V transformer.

I have the following questions. I did not want to create separate threads so please all questions below:

1. Can the UPS be used on hospital critical branch and equipment branch in terms bridging the gap between time two sources switch? Is it in NEC 2017 anywhere? I could not find in NEC 2017 Section 517

2. Is there anything in NEC 2017 regarding what are the running times of the UPS should be minimum?

3. How can one size the switchboard feeder breaker feeding the UPS and also the panelboard main breaker fed from the UPS? Is it in NEC 2017 anywhere?

4. Would the UPS transformer need to be grounded by grounding electrode conductor? They are internal to the UPS provided by manufacturer

5. I noticed that UPS-CR-1 is feeding 1200A panelboard while its sized 300kVA. I think it maybe to small based on 1200A panelboard. Is there anything in NEC 2017 that says to size the UPS or they have load shedding anywhere?





Riser Above:



UPS-RAD internal wiring above



UPS-CR-1 Internal wiring



UPS-CR-2 internal wiring diagram

 

[d0nut]

1. Can the UPS be used on hospital critical branch and equipment branch in terms bridging the gap between time two sources switch? Is it in NEC 2017 anywhere? I could not find in NEC 2017 Section 517

2. Is there anything in NEC 2017 regarding what are the running times of the UPS should be minimum?

3. How can one size the switchboard feeder breaker feeding the UPS and also the panelboard main breaker fed from the UPS? Is it in NEC 2017 anywhere?

4. Would the UPS transformer need to be grounded by grounding electrode conductor? They are internal to the UPS provided by manufacturer

5. I noticed that UPS-CR-1 is feeding 1200A panelboard while its sized 300kVA. I think it maybe to small based on 1200A panelboard. Is there anything in NEC 2017 that says to size the UPS or they have load shedding anywhere?

1. Yes. A UPS is not prohibited, therefore the NEC does not address it.
2. No. That is a design decision. If you are going to the trouble of adding the UPS units, I would make sure the run time was longer than any transfer switch delays.
3. The UPS manufacturer will have the required input breaker sizing. The output side probably doesn't matter because the UPS will most likely have an output breaker.
4. The UPS transformer will have a bonding jumper. It will also have an EGC on the input.
5. No. I would guess that the UPS was sized for the actual load rather than the existing equipment size, resulting in the mismatch. Feel free to ask the engineer of record for the load calculations if that will help you feel better about the design.

 

[hhsting]

1. Yes. A UPS is not prohibited, therefore the NEC does not address it.
2. No. That is a design decision. If you are going to the trouble of adding the UPS units, I would make sure the run time was longer than any transfer switch delays.
3. The UPS manufacturer will have the required input breaker sizing. The output side probably doesn't matter because the UPS will most likely have an output breaker.
4. The UPS transformer will have a bonding jumper. It will also have an EGC on the input.
5. No. I would guess that the UPS was sized for the actual load rather than the existing equipment size, resulting in the mismatch. Feel free to ask the engineer of record for the load calculations if that will help you feel better about the design.

Item #4 would Grounding Electrode Conductor be required at the UPS transformer?

Item #3 the load side of UPS thats panelboard main breaker size match the UPS internal output breaker size?

Item#3 the line side of US thats switchboard feeder breaker size match the UPS internal input breaker size?