UPS reserve capacity and sub panel

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tatilio2

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I have a customer with a UPS rated for 80,000 Kva
A phase draws 85 amps, B phase draws 84 amps, C phace draws 104 amps
Phase to neutral is 117 volts, and Phase to Phase is 204 amps.
Existing panels are full. Equipment never is power down.

What is the reserve capicity on the UPS and what size sub panel could be added?
 
I will guess that you meant 80kVA.
80kVA @ 208/120V, gives you approximately 220A per phase with a perfect power factor. As the power factor lowers, your amperage available will be less.
 
Check the UPS rating before you close in on 100% kVA load. You need to check what your load PF & kW, and the rating on the UPS for PF and kW. Although, it looks like you have quite a bit of room.
 
... capacity

... capacity

Total VA = 117 * (85 + 84 + 104) = 31,941 VA
80,000 VA - 31,941 = 48,059 VA
48059VA/208V/1.732 = 133 amps

That existing 80kVA UPS should easily accommodate a 208V, 3 phase 100A MCB panel.

JM
 
be careful here. is this your customer's own UPS or is it some sort of colocation environment?

Often datacenter cabinets are provided with one or more 20a circuits (for which the customers pay dearly) and usually the current draw on each circuit goes up over time as equipment is added, and you will find every circuit maxed out.

if its a colocation environment, dont provide branch circuits fed from the ups that would exceed the UPS's capacity if you add up all the circuit capacities.
 
be sure to use the kw rating for your calculations. most UPS's are rated at .8pf which means an 80kva is only a 64kw machine. most of the pf's that i see on UPS's are between .9 and .95 so the kw rating will be hit before the kva limit. for the reserve time on the battery here's a formula that i use.

KW / Number of strings / batteries per string (usually 30 or 40) / 6 (cells per battery) = wpc

you can look up the battery's spec sheet to see how long it will last at the given watts per cell. for example a C&D UPS12-400MR will last 15 minutes at 475 wpc or 20 minutes at 380.

you have to use the data sheet from the battery manufacturer because discharge curve is not linear.
 
Can you have the customer check the UPS?


Most UPS will have a blatant display that will show you exactly how loaded it is...

you can get a pretty exact gauge of where you are sitting from that.
 
tatilio2 said:
I have a customer with a UPS rated for 80,000 Kva
A phase draws 85 amps, B phase draws 84 amps, C phace draws 104 amps
Phase to neutral is 117 volts, and Phase to Phase is 204 amps.
Existing panels are full. Equipment never is power down.

What is the reserve capicity on the UPS and what size sub panel could be added?
Click to expand...
UPS rating 80KVA @ 204/120Volts its sure has .8PF

so rating current at PF=1 (load PF) as this is the most famous in telecom equipment or same.
then rated current is (80000/3/120)*.8 = 177 Amps.

in your case you have highst phase is down 104Amps then it seems like you have 177-104= 70 Amps available but!!!!!!!

take care as the 104 Amps is measured current not design current to loads so you should go to the loads connected to UPS and calculate the total rated currents from load's name plate, compare this with the rating of UPS that caculated above, if you found that you have availability then connect extra loads other wise don't connect any thing.
 
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