Stacked Second UPS Behind First Problem

[JVANHENGEL_apc]

This was originally posted on APC forums on 12/11/2009

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Hi All, Ok here is the problem.
We have a proprietary server that has an APC Smart ups 750 connected to it.
They have hard coded the software to start a system shutdown 1 min after power failure.
We have a 20kw auto genset, but if it is not used for a while it can take up to 90 seconds to settle down and run smooth under load.
So we plugged the APC unit into a Cyberpower 1500avr that is use to power 2 other servers to act as a temp power source until the Genset is up and stable.

Here is the problem:
While the other servers stay up fine, the APC goes nuts. Constantly clicking and switching. This causes the server connected to it to shutdown. Restarting this system can take up to 10 mins and our POS stations are offline while this happens. The load on the Cyberpower is less than 30% and show a runtime of 20 mins.

Tests:
1. APC unit by itself. Provides battery while power is off until Gen is stable, but powers down the server if gen is not ready within 1 min.

2. APC hooked to Cyberpower by itself. APC goes nuts until the power or Gen is restored.

3. APC hooked to Cyberpower with other servers. APC goes nuts, other servers remain online and stable.

I am assuming the problem is somthing to do with the waveform output by the Cyberpower unit.

I need to put a UPS infront of the APC unit to extend the run time.

Will a second APC unit work OK? Or will it have a problem with that also?

Thanks
John

[voidstar_apc · Accepted solution]

This was originally posted on APC forums on 12/11/2009

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Looking at the [spec for a CyberPower 1500avr unit|http://www.cyberpowersystems.com/user-manuals/CPS1500AVR-HO_UM.pdf] I notice this:

>
UPS-Output On battery output wave form: Simulated Sine Wave Form
>

A simulated sine wave looks different than normal AC power, and I wouldn't expect any line-interactive UPS to accept that. You need a UPS that puts out a true sine wave, such as the [APC SmartUPS 1500VA|http://www.apcc.com/resource/include/techspec_index.cfm?base_sku=sua1500i].