Generator Voltage Question

[jimainiac]

I have two portable generators that I keep on hand in case of power outages, and when I test them occasionally I plug a light in or a power tool to make sure they're producing electricity. Recently I tested them with voltmeter, and one of them is producing approximately 140 volts and 280 volts. The other is producing more like 130 and 260 volts.
We had a power outage today and I used the one that puts out around 130 volts for a couple of hours for the fridge and the freezer and the well pump, and all went well.
My question is, what is acceptable voltage? It makes sense that they would be set to produce a little on the high side with no load.

 

[robstaples]

I'd plug in a 1500 watt ( biggest you've got) electric heater and measure the voltage again. Most big units have automatic voltage regulators to compensate for load variations. Yours may not or is in a failure mode. My neighbor's Generac 15kw generator had a failed AVR and had 144 and 290 volts during an outage. It went to 330 volts with no load. No problems reported but really bright lights in the basement!! Over voltage is not recommened, but lots of equipment can handle it. Unfortunately, hard to know which in advance. I'd get it fixed. Overvoltage failures are generally totals ( cost more to repair then replace).

 

[skyhook]

I have two portable generators that I keep on hand in case of power outages, and when I test them occasionally I plug a light in or a power tool to make sure they're producing electricity. Recently I tested them with voltmeter, and one of them is producing approximately 140 volts and 280 volts. The other is producing more like 130 and 260 volts.
We had a power outage today and I used the one that puts out around 130 volts for a couple of hours for the fridge and the freezer and the well pump, and all went well.
My question is, what is acceptable voltage? It makes sense that they would be set to produce a little on the high side with no load.

Try a different volt meter and see what you get.
A "true RMS " meter will give you the correct voltage, and it will be lower.

 

[Looking4new]

Try a different volt meter and see what you get.
A "true RMS " meter will give you the correct voltage, and it will be lower.

Where are these meters available? What is their brand name?

 

[skyhook]

Where are these meters available? What is their brand name?

"Fluke" makes a good true RMS meter, there are many others, just look for a "true rms" digital meter.

 

[tcartwri]

Where are these meters available? What is their brand name?

CDN tire. Also, just check the batteries in your current meter. They may be done.

 

[robstaples]

Before a different meter,, measure your utility voltage in your house. Use that as a standard. Most homes are in acceptable range.

 

[davesl708]

Before a different meter,, measure your utility voltage in your house. Use that as a standard. Most homes are in acceptable range.

The thing to remember is your house voltage will fluctuate depending on the current load (at plant) and power factor.
Most equipment is designed to operate with voltage ranges of 104 to 140 and 208 to 280. The high and low ranges should be avoided. Household current should be between 115 and 120 per leg in most areas.

 

[buickanddeere]

The better generators use regulators. The cheaper generators saved $2 and use just a rectifier to excite the windings.
One of these days I'm going to toss the rectifier in my spare 5500 Generac and replace it with a regulator.
The output voltage at the power plant does not drop with load. The voltage drop at your electrical service many miles away from the utility generator is caused by I2R losses in the utility distribution lines.

 

[MNBobcat]

You can plug a UPS (Uninterruptable power supply) such as for powering computers into it and the plug what you are powering into the UPS. The UPS will clean up the power.

 

[k0ua]

You can plug a UPS (Uninterruptable power supply) such as for powering computers into it and the plug what you are powering into the UPS. The UPS will clean up the power.

But keep in mind some UPS's themselves are finicky about the input power, and will switch to battery mode and back, and keep on cycling. Some have sensitivity adjustments that you can lower to help prevent this.

 

[MNBobcat]

But keep in mind some UPS's themselves are finicky about the input power, and will switch to battery mode and back, and keep on cycling. Some have sensitivity adjustments that you can lower to help prevent this.

Interesting. I have higher quality APC units and they don't have any sensitivity adjustment and ran fine on my generator. Never even knew there were differences where it might not work!

 

[k0ua]

Interesting. I have higher quality APC units and they don't have any sensitivity adjustment and ran fine on my generator. Never even knew there were differences where it might not work!

Several of the higher end APC's do have a sensitivity adjustment.. Look in the owners manual. I had to adjust one of mine is how I know about that But if yours works fine as is.. don't mess with it.:thumbsup:

 

[eddie48]

You might, also, check the speed of the engine. Most generators are designed to work at the proper voltage at 3600 RPM. If your engine is running at 4000 rpm, the voltage will be higher.