peak versus Avg

Anonymous user · ‎2021-06-26

In a data center with dual UPS systems of 100KVA, each UPS shows about 25% peak , avg 16% load on the panel. Do I use the peak or the Avg to determine available capacity? I can't go over 50% right? So do I have 25% capacity left or 34%?
Thanks

upsguy_apc · ‎2021-06-26

Code typically specifies the 80% rule for things like breakers so that you would only run a 20A breaker at 16A max. However UPS are designed to run at their rated 100% limit indefinitely. So if you two 100KVA UPS you can run each up to 50KVA if you plan on having your load fail over to the other UPS during a failure. If that was to occur and you had exactly 50KVA on each then the online UPS would assume the other 50KVA and run at 100kva 100% load as long as you needed to. The only issue you run into with fully loading a unit is that loads often fluctuate and can cause an overload condition which is why some data center managers choose to stay below their max by an order of 10 or 20%. In your case since you have 100KVA units I'd run them up to 45% and in a fail over the online UPS would still be loaded at 90% and would give you 10% of extra capacity if needed.

See Answer In Context

Anonymous user · ‎2021-06-26

To clarify he cannot go over 50% of BOTH units capacity. IOW, he can load up tp 100kva total. Persoanlly I would stay below 80%.

Anonymous user · ‎2021-06-26

Thanks for the responses!

I was plannning on keeping each UPS below 40% so in a failover one UPS would stay below 80%. Is that a code requirement or just a best practice?
Code does require all circuits to stay below 80%, right?

Thanks Again!

upsguy_apc · ‎2021-06-26

Code typically specifies the 80% rule for things like breakers so that you would only run a 20A breaker at 16A max. However UPS are designed to run at their rated 100% limit indefinitely. So if you two 100KVA UPS you can run each up to 50KVA if you plan on having your load fail over to the other UPS during a failure. If that was to occur and you had exactly 50KVA on each then the online UPS would assume the other 50KVA and run at 100kva 100% load as long as you needed to. The only issue you run into with fully loading a unit is that loads often fluctuate and can cause an overload condition which is why some data center managers choose to stay below their max by an order of 10 or 20%. In your case since you have 100KVA units I'd run them up to 45% and in a fail over the online UPS would still be loaded at 90% and would give you 10% of extra capacity if needed.