Design Build UPS Project

[GSXR600]

Hi,
We are working on a design build UPS project. We are installing a 45 KVA UPS system. The max current is 166 amps. However the recommended over current protective device is 200 amps. We only have spacing to hang a 45 KVA transformer in the room which will limit me to 175 amp OCPD.

I am looking for someone with a little more UPS back grounds advise on if this could cause any unforeseen issues down the road. In my vision we are not limiting the customer on the 45 KVA they purchased and that the UPS manufacturers recommended OCPD is over sized by one size.

 

[rcwilson]

If this is the supply to the UPS battery charger input, there will be a problem. A 45 kVA UPS puts out 45 KVA but has to take in more power to cover charger and inverter losses and to recharge the batteries after a power outage.

If it is only a bypass transformer to supply an alternate source for the output transfer switch, it might be OK.
Depends on how much risk you are willing to take by not following the manufacturer's instructions.

 

[ron]

Bob is absolutely correct. The input feeder will be larger than the output, often by 120% to account for loses and battery recharge.

45kVA UPS will put out 45kVA and likely take in 54kVA.

 

[GSXR600]

thanks guys I figured that's the response I would get. Have you guys ever hung a 75 KVA transformer from ceiling. Im not a huge fan :/

 

[GoldDigger]

thanks guys I figured that's the response I would get. Have you guys ever hung a 75 KVA transformer from ceiling. Im not a huge fan :/

I've hung huge fans from the ceiling....:lol: