taoshum said:
When we were in Mx last fall, the line voltage was usually about 132VAC. Sometimes it would get up to 134VAC. When the A/C was on it would drop to 128VAC. Two questions. One, how high is too high? Two, which of these voltage control boxes would limit the high voltage and the low voltage and what are the ranges? I walked around the RV park and I found one RV that was using a line conditioner that would "compensate" for low voltage but did nothing about high voltage. Everyone else, as best I could tell either by looking or asking, did not pay any attention to the voltage.
I don't think we damaged anything... all of the appliances still seem to work ok but I did fret about it.
Thanks, G.
The first thing to consider is that many of the voltage meters out there aren't very accurate. I have a Camco plug-in voltage meter -- with the yellow plastic housing and the meter with the green and red zones. I plugged it in and it reads about 8 volts higher than my digital test meter which while not of unimpeachable calibration ought to be within a volt or two.
I would expect that anywhere in 110-125 volts would be fine for any well-designed appliance. Beyond that, it depends.
Some computers and electronics have switching power supplies that will run just fine on any voltage between 90 and 260. The higher the voltage, the less current they draw. Often, if these have a voltage switch for 120 and 240, it doesn't do anything but change the fuse size.
Then again, some cheap electronics have poorly regulated power supplies and might be destroyed by overvoltage.
I suspect that most of the modern converters based on switching designs are also relatively unaffected by overvoltage. Older converters, based on linear designs, will run hotter on higher voltages.
Heating appliances, like toasters, coffee pots, space heaters, hair dryers -- will produce 21% more heat with a 10% increase in voltage. That's enough that they may overheat.
Induction motors, like those found in A/C units, will draw somewhat less current at a higher voltage but will still run slightly hotter and be more prone to overheating. Induction motors are most efficient (and run coolest) at their design voltage and run hotter on either higher or lower voltage.
Regarding your second question, in general, the autotransformer-based buck/boost voltage regulators, sold by Autoformer and their competition, can compensate for overvoltage the same way they compensate for undervoltage but in reverse.