UPS draws extra power for charging, which overloads generator: How solve?

[BillP]

Hello!

This is a new one for me...

We have two backup generators. One powers the server room, one powers the workstations.

When the power went out today, we were surprised to discover that the workstation generator (2000 watts!) could only support two workstations (it should support 4-6). We believe the reason is that the four SmartUPS-1500's attached were charging, and that the charging was pulling 100-250 watts per SmartUPS.

Now we don't want to disable/bypass the UPS (that is how we can move the power source from the wall to the generator, and that is what protects us from the generator running out of fuel, etc.).

The questions:

1) What do we think the power draw is for charging (say it is a SmartUPS-1500 with %50 charge) ?

2) Is there a way we can disable charging, while preserving the battery backup feature, so that we can keep the UPS in the picture, but reduce the load on the generator during a power outage?

Thank you!

[BillP · Accepted solution]

Thank you!

So if I have 10 workstations, each with a SUA1500 attached, the math is like this:

Workstations: 400 watts each (with displays, phones, usb devices)
Smart ups charging: 135 watts each
2000 watt generator (that gives about 1600 watts sustained)

2000 watt generator supporting workstations only: 3 or 4 workstations

2000 watt generator supporting UPS-attached workstations: 2 or 3 workstations


The above is, actually, exactly what my direct experience indicates.