APC Smart-UPS SC 450 won't hold load

[Anonymous user]

I'm helping clean up a rack of a/v equipment installed in our condo clubhouse after having suggested that all that expensive stuff really should be protected by a UPS. To find out how large a UPS might be needed, I'll pulled the plug from the wall so I could insert a test power cord that would allow me to take a reading with my amp clamp. Surprise, when I pulled the plug, I heard a beeping that sounded like a UPS alarm. Meanwhile I got my amp probe hooked up, and measured the total load at 1.4-1.5 amps @ 120VAC = 180VA.

Turns out there is an APC Smart-UPS SC 450 mounted in the rack that was hidden. But it also had nothing but one small device plugged into it - all the expensive stuff was plugged right into the wall via a buss strip (which the UPS was also plugged into). So I rearranged the wiring so the UPS was plugged into the wall and the UPS was plugged into the buss strip, allowing the UPS to take the whole load of the rack.

But the UPS immediately went into a cycle of powering up, beeping, and shutting down. No indicator lights on the front panel. So took it back out of the loop.

Could this be a symptom of a faulty battery? I don't know how old this one is - it could be 10 years old. It runs fine with whatever tiny load that one small device puts on it, but not with the load of the whole rack.

And I wondered if my amp clamp was reading wrong, so I brought it home and hooked up a 900W toaster. The amp clamp read 7.4A - right on.

I don't have any problem replacing the battery if that's the likely cause. Just want some confidence that this is the case, and not that the UPS itself is messed up.   Thanks! 

[voidstar_apc]

My thoughts:

- For protection a surge strip would be cheaper and less maintenance. UPSes are usually used when you need to work through a power outage or safely shutdown during an outage.

- The SmartUPS SC 450 handles at most 250W. Inrush can be greater than steady-state current. It's not a lot of power to handle the whole rack. I would expect to see an "overloaded" light on the front panel in this case though.

- Batteries last 3-5 years. If nobody knows about the UPS, the battery has probably not been replaced. The manual mentions the lights will remain off if the battery drains, but doesn't mention a restart loop.

My money's on a dead battery + overloaded.

[BillP]

I would start with replacing the battery/batteries. These units do funky things when the batteries go bad.

[MarkC_apc]

To "P";

The load capabilities of the SC-450 is very limited - I've found that although the total wattage of my LCD TV and Receiver is below the UPS rated wattage, it will not support both.  As Voidstar stated, the overload light should come on.

[Anonymous user · Accepted solution]

Thanks for all the replies.  Will start with replacing the battery and see if that works. Will be disappointing if it won't hold the load.    PL