I am trying to find out the acceptable plus and minus voltage for a
240v water heater. My voltage went up to 250v and whirlpool told me
that is the reason my element burned up. My power provider said it
should be within tolerance. I can't find any + or - specs on their
Most electrical appliances can easily withstand + / - 10% voltage
fluctuation. So even if the voltage spec is 230 volt which most are, you
would be safe at 250 volts, but right a the edge of the tolerance.
It's not fun living on the edge. Your power company is required to
keep line voltages to acceptable standards, generally + or - within 5%
of the nominal rated service voltage. All utilities have departments
that monitor these things and they should be willing to send out a
technician and put a time sensitive voltage chart recorder on your
line. (The overvoltage may actually be higher than 250 V. during
periods of light loads such as the early morning hours).
A fix can sometimes be as easy as your utility changing a tap on your
service transfomer. What you need to do is convince them that you
do, in fact, have a problem.
In addition to the possible burn-outs of appliances such as you
experienced, sustained overvoltage produces wasted power (in the form
of heat) which is metered and paid for by the customer.
IEEE 519 says utilities are to regulate voltages to plus 10 and minus 7%.
Unfortunately the next paragraph says "except for short periods of time".
Is a day a short period of time compared to a year, you get the idea.
Your nominal voltage is probably 240v so a 10 volt increase is about 4%.
Well within the tolerances in the US.
Another case of the help line not having a f'''ing clue.
You do not mention how old the element/heater are. Elements immersed in
mineral rich water tend to last less long as elements in less mineral rich
water. Flushing the heater regularly can prolong the elements life.
Out of curiosity how do you know that the power went up to 250v? Measured by
peak or rms method?
Peak method is not the most accurate method of measuring voltage. RMS is
what I use.
I just measured the voltage with a voltmeter going into the water
heater. (with the wires disconnected from the water heater) The water
heater is only one month old and Lowes is going to replace it so I just
don't want the same thing to happen.
When you get the new heater or element installed measure the voltage at
the heater with the wires connected and the heater drawing current.
Chances are you'll find the voltage a bit less than 250 because of a bit
of voltage drop in the wires going to the heater.
I seriously doubt if 250 volts rms is what caused that element to fail
so soon. I think it was just a fluke caused by a defectively
Are you experiencing rather short life of the lightbulbs in your home?
If the voltage is really excessive that'll happen.
You coulda told the full story up front.
It would've been pretty obvious that you had defective element(s) or
powered the unit up dry.
Open-circuit voltage is meaningless; of more significance would have
been current draw at element, vice rating.
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