Well, my old nemesis ComEd has reared its head again.
Last night, I had another beep hunt. This was a steady, rapid beep, so it only took about 30 seconds to find the problem: The alarm was going off on the UPS protecting the television and TiVo. It’s a fairly dumb UPS, so there’s no way to tell what the problem is, but I figured it was just the battery. I shut it off and unplugged it, and I plugged our television gear directly into the wall. Problem solved. I could replace the UPS later this week.
Then, about 4:30 this morning, I woke up to more beeping. This one was a little harder to localize for a reason I couldn’t quite figure out, but I eventually traced it to the UPS protecting my work computer.
This was a bad sign. One UPS alarming is probably a battery problem or some other end-of-life issue. Two UPS alarms is a problem with the electrical power coming in to the house.
I had shut down that computer for the weekend, so I just turned off the UPS to stop the alarm…and I realized that something else was still beeping somewhare in the house. That’s why I had trouble figuring out where the beep was coming from! I was hearing beeping from two sources.
The other alarm turned out to be the UPS protecting my wife’s computer. It had tripped out and turned off the computer, so I just turned off the UPS to kill the alarm. This time it worked. Silence.
It took me a minute to find my DMM and another to find a pair of probes, but with the dial set to measure AC voltage, I stuck the probe tips into an outlet in the kitchen: 138 volts.
That’s high. American residential electricity is supposed to be about 120 volts, with houses closest to the transformer getting a slightly higher voltage, and houses farthest away getting a slightly lower voltage, plus some variation during the day due to the changing load.
So it was high, but how high is too high? Surprisingly, that’s not an easy thing to find out. The ComEd site has nothing about it that I could find, and the Citizens Utility Board site is useless: Lots of stuff about rates, but nothing about the power supply specification.
I eventually found what I wanted in the ICC regulations governing electrical voltage in Illinois (emphasis mine):
Section 410.300 Voltage Regulation
a) Standard voltage. Each entity supplying electrical energy for general use shall adopt a standard service voltage of 120 volts (when measured phase to neutral) and shall maintain the service voltage within the allowable variations from that value at all times.
b) Allowable voltage variations. For service rendered at the standard service voltage, voltage variations as measured at any customer’s point of delivery shall not exceed a maximum of 127 volts nor fall below a minimum of 113 volts for periods longer than two minutes in each instance. For service rendered at voltages other than the standard voltage value, voltage variations as measured at any customer’s point of delivery shall not exceed 10% above or below the service voltage for a longer period than two minutes in each instance.
So it was definitely way too high.
While I was writing this, the lineman showed up. He was a friendly guy, and he seemed to take the problem seriously. (I suspect ComEd gets a lot of complaints about “the voltage” from crackpots, so I’ve been trying to act as sane as possible so they take me seriously.) I let him into the basement to check the voltage at the meter, and he measured it at 139 and 140 VAC.
The UPS on my main home computer is bigger and more expensive than the other three, and it has a voltage regulation feature, so that computer is still working, and I’ve plugged my work computer into it so I can do my job. However, I’ve got most of the household electronics shut off, and I also shut off the air conditioner, because I’m concerned that the compressor will overheat on the high voltage.
So now I wait. They’ve seen the problem. Now I just need them to fix it.
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