Minimum safe voltage for appliance motors

I recently had a brownout due to weather related power grid issues. The voltage on my 120 volt circuits was down to about 100-105 volts.
Any feedback regarding safe voltage range (specifically minimum) for motors in refrigerator, freezer, sump pump and furnace blower? I do want to protect these items while at the same time it is nice to let the furnace run when it is 15 degrees out!
Thanks...
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motors
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IEEE says plus 10% minus 7% of nominal voltage. The very next paragraph says except for short periods of time. Gee guess who wrote that?
It is always nice to keep the voltage in the sweet spot. But that is not always possible. Installing low voltage relays to open on low voltage seems excessive to me. Unless the motor is starting with a low voltage condition I would not be concerned.
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SQLit wrote:

Hi, If you hook up power monitor on your line for a period, you will be surprised at what you see. Spikes, sags, frequency swings, etc. This things go on all the time in real life.
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For the most part you can trust the utilities to kill the power completely if it goes outside of the safe-for-equipment range. They have a tendancy to have to pay for equipment damaged by operating decisions such as this.
Their equipment will automatically kill the system if they can't keep the voltage high enough.
For the most part, I believe that 90V is considered the minimum safe value for medium term brownouts, and 85V for _very_ short ones.
The equipment at highest risk are the compressors in your fridge or freezer.
In an extreme brownout, I'd be tempted to turn them off so they won't cycle, and turn them on for an hour every 4-6 hours to do one long cool-down run.
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Chris Lewis wrote:

They would like too but thats not always possible. Most brown outs I have experienced were caused by the local transformer loosing a branch. Not sure they can stop that. But its all so rare. I experience one about every 6-8 years.
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For the most part, electromechanical systems will not be bothered by the type of undervoltage you describe. Things with mainly motors and switches may loose torque but should still function at 100V. Much lower and relays cannot hold their position and things tend to shut down.
Devices that are microelectronic may or may not be bothered by low voltage. Most newer electronic devices with switching power supplies can withstand a very wide range of supply voltage and be unaffected. Look at the nameplate for each appliance or device you have to see what it is rated for.
If you do damage a major appliance, that would probably be covered by insurance if you cared to make a claim.
Did you have anything fail after this brownout, probably not. Overvoltage spikes due to lightning or equipment failure cause most of the damage. A whole house surge protector installed in the breaker panel and more surge protectors (point of use) at sensitive stuff like computers and TVs (though these probably have that function built in) is the best you can do without installing expensive UPS equipment.
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I work in a few industrial plants where the 120 volts runs about 100 volts.....never noticed any real problems with equipment etc..... the 208 runs about 187 188....still no noticebale problems even though equipment might not be operating as efficiently as possible.
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