SmartUps 3000 drops load for 1sec at power failure

[Anonymous user]

Hi Folks,

I have a fairly old UPS; Model SU3000R3IBX135k, build year 1999.

Been working well for a long time, but recently started dropping load briefly every few weeks. Batteries were about 4 years old so I got a new set in hopes that would keep it going for a bit longer.

New batteries installed; Powerchute says they're ok and at 100%.

Load at 21%.

Did a failure test by switching off the power outlet. All equipment attached to the UPS immediately turned off, and about half to one second later powered back up. From this point the UPS seemed to have no trouble running everything on batteries. Restoring power a few minutes later behaved as expected.

Questions:

1) Are there components in the UPS that commonly fail on old units which would cause such a delay in power failure detection and cut-over to batteries?

2) I also have an APC automatic transfer switch in the mix wired as follows; any chance this would cause a delay in the UPS switching to batteries on legitimate power failure?

Supply ------ [UPS] ----- {ATS} Load

Supply----------------------- {ATS} Load

Same supply - split with a double adapter. 2 inputs into one ATS; straight from outlet, and from UPS. Equipment connected to ATS output.

Rationale was if the UPS had a freakout and dropped load, or needed offline maintenance the ATS would cut to straight wall power and things continue running.

I'm concerned I may have shot myself in the foot with this; Perhaps the ATS detects failure on primary source (UPS), switches to backup - which is also gone since it is the same supply, and then switches back to UPS which is now on batteries, but with all the switching around time the gear has now dropped.

Does that seem plausible?

Cheers,

-Martin.

[BillP · Accepted solution]

What model of ATS do you have? Does either device have any log files during these drops we can review?

You're right on the ATS - this is not a recommended set up and sort of defeats the purpose of an ATS because you are ultimately using the same input power source/circuit. The ATS ideally should be connected to two separate UPSs on two separate power circuits.

Either way, I think we should take the ATS out of the mix somehow because you need to determine if this is a problem with the ATS or the UPS. Maybe switch the preferred power source of the ATS to JUST the supply source with no UPS and repeat the test to see what happens?

What you suspect is definitely feasible with thrashing between sources somehow. My advise though is to at least start by testing JUST with ATS and just with UPS to narrow it down. It could be a problem with an output relay or other UPS or ATS component but I can't tell for sure with what we have so far.

[Anonymous user]

Hi Angela,

Thanks for your response & advice. The ATS is a simple old apc one; SU044-1.

I went ahead and took the ATS completely out of the picture by hooking the load directly to the UPS and things work well again, so I was clearly doing something dumb with having that in there fed by the same supply. Looks like they get confused and step on each other in that setup.

Potentially the ATS sensitivity could be tuned to survive this scenario, but considering I don't have a 2nd independent supply anyway I think I'll just simplify things and keep it out.

Cheers,

-M.

[BillP]

Thanks for the update. And yes, SU044-1 is quite old. Glad we narrowed it down though.