May 24, 2005
Engineering Department
VAC
Here's a question that's turning out to be harder to answer than I would have thought: What's the acceptable voltage range for your house?
A few days ago the lights flickered and the speakers on one of my computers started making funny noises. Turns out they're fried. That computer system wasn't on a UPS, so I went out and bought an APC Back-UPS 800 for it.
When I plugged it in, it wouldn't go on-line. It would provide power from the internal battery, but it refused to pass through the power from the wall outlet. Reading through the troubleshooting materials, I decided either the UPS was busted or there was something wrong with the household power. This latter possibility made some sense, as my other UPS had started switching to battery several times an hour.
I don't know much about electricity, and I have no real idea how to evaluate electrical noise, so I checked the only thing I know how to check: Voltage. Household power is supposed to be at 120 volts and when I've checked the wiring on outlets, I've usually seen something close to that.
When I check now, however, I get a reading of 135 volts, give or take a volt. I figured out how to hook two of the UPS boxes up to my computer, and they are reporting about 137 volts.
That's high, but is it too high?
I assume ComEd has a commitment to provide electrical power of a certain quality. Somewhere there's a spec that says what voltage range is acceptable. For example, if voltage is allowed to vary 5%, then ComEd would have to deliver household power at somewhere between 114 and 126 VAC.
I've tried to find out what this is, to see if I would be justified in calling and complaining, but I can't find it anywhere. The ComEd website has all kinds of information about bill payment, energy prices, and safety, but nothing about the specifications of their product. They invite me to report blackouts or downed wires, but they don't tell me what to do if the voltage gets out of spec.
The local Citizen's Utility Board website is also useless. Lots of stuff about regulation and pricing, but nothing about the quality of ComEd's product.
Well, I've had equipment damage, my UPS rejects line power, and the voltage is measurably high, so I decided to call the blackout report number on Friday and complain. I called again on Monday. On Monday evening a couple of trucks were parked next to the pole with our transformer on it. They were there at least half an hour. However, nothing has changed: I still measure 135 volts.
Also, one of the quartz-halogen lights just burnt out. Was it about due, or was it hurried to its demise by the high voltage?
So, am I getting poor products and customer service from a big corporation that has a monopoly? Or am I the crazy guy who keeps calling to complain about the voltage? And even if I'm crazy, what do I do about the UPS that won't work in my house?
Update: In something called The Information and Requirements For The Supply of Electric Service provided by Exelon (ComEd's parent company) section 1.051(a) says:
On the Company's 120V standard, the range of acceptable voltage is 127 volts maximum and 113 volts minimum.
So I'm right. The power supplied to my house doesn't meet spec.
Now the trick is getting them to fix it...
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