Dual UPS - Autonomy Timer setting

[NickParker]

We have Dual Stand alone UPS ( similar to the below picture) from which both the single and dual cord loads are to be fed.
The single corded loads are fed via STS and the dual corded loads are fed via two separate cables from the UPS A & UPS B.

For this system, the backup time of the battery banks A & B is considered as 50% of the total backup time according to the client spec.
It means, for a load with an autonomy of 30 mins, each battery bank is sized only for 15 minutes for that particular load.

If both the AC Mains and the Bypass power input fails in both the UPS, the battery has to power the loads. I'm planning to use Timers to trip the Circuit Breaker once the autonomy time (50% per each battery bank) is elapsed.

The issue here is, how do I ensure that load cuts off in the specified autonomy time when fed from the batteries? I do not want one battery bank to drain completely.
For the dual corded loads - Both the UPS A & UPS B will have its own circuit breakers- how the scheme for autonomy timer activation and cut off of loads to be implemented. Do I need to set the timer at 30 mins or at 15 mins for the particular loads?
For single corded loads - Do I need to set the timer in STS?

Thank you all!

 

[mparenteau]

1-line would be helpful...

Mike

 

[charz]

Hi Mike,

One line is attached.

 

[davidbeach]

How does the cooling continue to run if the incoming power fails? If you don’t have cooling you can simply use a thermostat and dump everything before the batteries run down.

 

[mparenteau]

I'll bite...why is it important not to have the UPS fully discharge its batteries? Can the rest of us assume you have no standby generation ahead of the UPS?

Mike

 

[NickParker]

@David: The cooling fans are powered from the output of UPS.
@Mike: There is a standby generation ahead of the UPS, however my intention is to load the batteries equally and the timer setting so that load cuts off after feeding for the respective autonomy.

 

[mparenteau]

Nick,

Maybe I'm missing something. If you have standby generation ahead of the UPS, the discharge time is only that time when utility power drops and the standby generation starts (typically under 30 sec). So is there a need for your timing circuit? What am I missing?

Mike