Monday, March 10, 2008


This is a VariAC; in this case, it's a VariAC that used to be sold by Sweet Marias, the specialty coffee dealer.

A VariAC, is one of those few technical items that does exactly what its name would suggest: it varies AC voltage (some also vary amperage; or rather they all do, but some offer control over amperage). People use them to vary the speed of AC motors (in tools for example), and the heat output of electric heaters (and lots of other reasons besides).

A good VariAC can take your standard 120 volt nominal line voltage, and vary it anywhere from zero, to 130 volts; by carefully balancing the output voltage, output amperage, and total current draw.

If you don't maintain that careful balance, presuming things turn on at all, they run erratically; or they get hot, and then they start to pop.

My house wiring seems to be hooked up through a cheap Chinese VariAC, with a crack addled monkey at the knob.

So a few weeks ago.. actually a few times over the past few weeks... I've mentioned that the power in my house is pretty dirty; and that it's caused some failures in my sensitive electronics.

It's cost me several thousand dollars in spare parts, and replacements over the last few years; but it was mostly gradual so I didn't really take notice of it. Then, over the course of less than three months, I had a half dozen computers and monitors die all at once.

Obviously, the issue was brought home to me right then; and it became very clear I needed to do something about the problem. So, I went out and bought power conditioning UPSes for all my electronics. Basically, if it's got any sensitive circuitry in it, it's now plugged into a power conditioning UPS.

So.. I knew the problem was bad... but I had no idea just how bad. Each power conditioner has a realtime input voltage display, as well as ground fault and line fault indicators.

Let me tell you, this has been a revelation.

Over the past few weeks, I have seen input voltages as low as 104vac, and as high as 127vac; as well as random line faults (which indicate spikes and dropouts), and flickering ground faults (which indicates poor connections to ground, or just poor grounding).

For those that are unfamiliar with electrical standards; this is FAR beyond the range of acceptable line voltage variation; to the point that it can cause failures and damage to electronics. The line and ground faults simply exacerbate the problem. A voltage spike combined with a bad ground is a nearly sure recipe for a blown power supply for example.

Though many electrical appliances are not greatly voltage sensitive; most consumer electronics in the US are designed to handle a maximum variation of 120vac +- 5%, or from about 115, to about 125 volts (actually generally 114-126). 23 volts of variation, is more than enough to destroy sensitive electronic equipment.

Just as an example, when I started writing this about 15 minutes ago, my input voltage was reading at 121vac. As I write this line, it's at 112vac.

A variation like that will also cause a noticeable dimming or brightening of incandescent lights, and noticeable changes in motor running speeds etc... And I HAD noticed such things before; but again, I didn't realize just how bad it was. Color me oblivious.

There doesn't seem to be any correlation between power use in the house and input voltage; or any particular daytime cycle to the variations. This would seem to indicate the problem is with my utility company (likely, my local stepdown transformer; because the local substations are supposedly monitored to maintain 5% variation from nominal voltage ), and not with my house wiring or any particular load in the house. Of course my house was built in 1953, and the wiring was only partially upgraded in the 70s, so I'm sure the inside wiring is no help to the situation; and neither are my rather old and inefficient oven, range etc... .

I guess it really IS time to go for a whole house power conditioner.

Oh, it's up to 117 volts now.