UPS I Did It Again

There's something rather disturbing about sitting on the sofa looking at a large brown water stain on the lounge ceiling while the mains electricity circuit breaker is occasionally tripping out. Somewhere in the back of your mind is the worrying thought that the two events might be connected. And that another stream of tradesmen, who will tear up the floor and bash holes in the ceiling, is imminent. And that's after three months of visits from men with toolboxes, and startlingly rapid deflation of my bank balance, during our recently completed house modernization saga.

Before I ramble on any further, however, I guess I should apologize both for the overuse of bad song titles (see also UPS Outside Your Head), and the strange focus on boxes with a big battery inside. As you probably guessed by now, we're back in what's turning out to be "interruptible-power-supply" land. And something I've never seen happen before with a UPS.

I've been using APC UPSs for more years that I like to remember, and generally they do what you expect. After a while, or when they get a bit too warm, the battery inside starts to expand and stops providing backup power, but for the rest of the time they just sit there - maybe flickering a few LEDs now and then, and beeping contentedly when the mains power goes off.

There's four 1000W ones in the server cabinet in my garage powering all of the hi-tech stuff you need to connect a few servers to the Internet and an internal network. One of the servers is a cold-swap backup Hyper-V host that can take over all the VMs if (or, more likely, when) the main host server dies. I power up the backup server once a week so it can sync Active Directory (and to check that it still works, you know what computers are like). When it's off I usually turn off its UPS as well, though that's still connected to the mains supply so the battery is kept charged.

But last week when I pressed the "1" button to turn it on (which automatically boots the server) it immediately tripped out the overload protector in the main fuse box for that ring main circuit. Could this be the cause of our mains electricity problem? But the server powered up fine running on battery so the inverter is obviously working, and the overload switch on the UPS was not tripped. Maybe it's a problem with the battery, though that seemed unlikely as it was powering the server, but I replaced it anyway and everything seemed to work again.

At least it did for a while. After scurrying repeatedly (often in complete darkness) for the fuse box reset button at various intervals during the next two days, and several other experiments trying to isolate the fault (isn't it amazing how many things you have plugged in around the house when you are trying to figure which one is playing up), I decided it needed more decisive action.

When I disconnected and removed the UPS from the cabinet it was quite warm, and an examination of the internal gubbins looking for stray wires or that familiar burning smell offered no clue. Could it just be the cold wet weather we've been having for a couple of weeks causing condensation inside? Yet we have cold wet weather every year (often it's the default climate setting here in England), so why should it suddenly happen this year?

However, after a day next to a radiator in a warm kitchen, I test the UPS and it's working fine again. It looks like it didn't take well to having a hurricane of freezing cold and damp air blown over it for a week while the server was powered down and not drawing any current. Though it did start tripping the circuit breaker again a few days later after I reinstalled it, even though I left it turned on this time. But I suppose it makes a welcome change to the more usual situation of trying to keep everything in the server cabinet from melting during the rest of the year. Maybe it's time to invest in temperature-controlled fans?

And the large brown water stain on the lounge ceiling? I do seem to remember having a bathing accident a while ago, at the time when the bath panel had been removed to lay the bathroom floor, so I'm fervently hoping that was the cause...

Footnote: After the UPS tripped the circuit breaker again I gave up and replaced it (there are good deals on reconditioned ones around at the moment). Perhaps I'll give this one another try in the summer to see if it's got over it's bad habit.

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