Using a generator to power a water well pump

[whistlepig]

We have a 6500 watt Honda and the well pump doesn't lug it. Can't even tell when the well pump kicks on by listening to the generator. The only thing that I can hear a load on the generator is when I plug in an electric skillet.

 

[arrow]

You have adjusted the throttle down? This will reduce the frequency and voltage and you risk burning up things like freezer and refrigerator. Highly not recommended. Your motors will run hotter. What frequency are you running?

Good question Bob. I have no idea nor do I know how to measure it as my multi meter does not have a "hertz" scale. I know I'm supposed to be at 60 cycles but do not know how to test for this. Thanks for your advice.

 

[Mickey_Fx]

For many, the simplest way to measure freq is to get a Kill-A-Watt meter, about $30. Among its many features/measurements is a freq meter.

Depending upon the qlty of the gov on the engine you may see engine speed change some over the full load range. I'd recommend setting engine speed with about half rated load on the generator.

 

[BobRip]

We have a 6500 watt Honda and the well pump doesn't lug it. Can't even tell when the well pump kicks on by listening to the generator. The only thing that I can hear a load on the generator is when I plug in an electric skillet.

How deep is your well and what horse power is the pump? A shallow well is a lot easier to start and run than a deep one.

 

[BobRip]

Good question Bob. I have no idea nor do I know how to measure it as my multi meter does not have a "hertz" scale. I know I'm supposed to be at 60 cycles but do not know how to test for this. Thanks for your advice.

You can take an old electric clock and time the second hand. Some of the newer ones do not vary with power frequency. It should not have a circuit board inside. It should take 60 seconds to go around. You can then adjust the generator engine speed. The kill-o- watt meter is excellent and a good tool for anyone using a generator.

 

[TheGoose]

Again, this is not necessarily true. I can have a 700' well here, but use a 1/2 HP pump. Or have a 100' well and use a 3-HP pump.

The only two things that really matter are the HP and the length of wire going down to the pump. More wire=more voltage loss.

How deep is your well and what horse power is the pump? A shallow well is a lot easier to start and run than a deep one.

 

[BobRip]

Again, this is not necessarily true. I can have a 700' well here, but use a 1/2 HP pump. Or have a 100' well and use a 3-HP pump.

The only two things that really matter are the HP and the length of wire going down to the pump. More wire=more voltage loss.

I agree that the water head is a factor, but the gauge of the wire also matters. I had to increase the wire size in mine.

The water must be accelerated by the pump to allow the pump to reach it's normal operating speed and current. If the pipe is longer, then more water must be accelerated. This keeps the current higher than normal for a longer time. Some generators may have problems with this. I bow to your greater experience, but I have seen the above currents on my well pump.

 

[arrow]

I don't really know what is meant by "adjusted the throttle down". Unless you're using an inverter style gen-set, all generators must rotate at the same speed, either 1800 rpms' or 3600 rpm's. The speed never changes, even during idle. Otherwise you would not get the 60 hz (60 cycles per second). 1800 rpm generators are most costly, but use less fuel. They have an extra set (or two?) of windings in them, I think 4 poles instead of two.

On the engine is a adjusting screw. I throttled the engine down as it seemed to be revving excessively. It is a Robin rated at 9.5 hp at 4000 rpm. If it came from the factory at 4000 rpm, its less than that now. It is rated for 10 hrs on a full tank (5 gal) at 50% load (5200-6250 surge) Mine can go 12 hrs on a tank at the rpm I have it running at and the load it encounters. I do not know if the math on rpms can ratio to be meaningful for cycle output. I also do not know if the engine needs to be at 4000 rpm to make up for the load of the generator itself. It has no problem running a 100 amp stick welder at its present rpm and I had no problem running multiples of anything. As to what this is cycling at in its present rpm state, I have no clue.

 

[TheGoose]

I'm not going to pretend that I know everything in regards to your statement, because I don't. What I do know is that you use more energy to move water than you do to pressurize it. For example, if you have a 1-HP pump set at 200' pumping 8 gpm, you might pull ~8 amps. If you were to install a throttle valve at the head and throttle that 8 gpm down to 4 gpm, you will pull less amps, like ~7ish. So using that logic you're using more electricity when you're moving the most water. I don't know if accelerating the water is factor. It all happens in a split second. The second the motor is energized is when it uses the most energy. The time from start to full rpm's is fractional.

I agree that the water head is a factor, but the gauge of the wire also matters. I had to increase the wire size in mine.

The water must be accelerated by the pump to allow the pump to reach it's normal operating speed and current. If the pipe is longer, then more water must be accelerated. This keeps the current higher than normal for a longer time. Some generators may have problems with this. I bow to your greater experience, but I have seen the above currents on my well pump.

 

[TheGoose]

Again, I might be wrong on this. I know we have some very smart educated people on here (EE Pete maybe?).....

The generator has to turn at either 3600 or 1800 rpms to get 60 hz. Oh sure the speed can vary a little up or down. I think most things have a rating for like 55-65 hz. Since the motor and generator should be direct coupled they need to turn at the same speed. When you put a load on and hear the engine "rev up", you're not actually increasing speed. You're using more fuel etc, but the speed should stay the same.

An inverter generator operates differently so you can idle up/down as necessary.

On the engine is a adjusting screw. I throttled the engine down as it seemed to be revving excessively. It is a Robin rated at 9.5 hp at 4000 rpm. If it came from the factory at 4000 rpm, its less than that now. It is rated for 10 hrs on a full tank (5 gal) at 50% load (5200-6250 surge) Mine can go 12 hrs on a tank at the rpm I have it running at and the load it encounters. I do not know if the math on rpms can ratio to be meaningful for cycle output. I also do not know if the engine needs to be at 4000 rpm to make up for the load of the generator itself. It has no problem running a 100 amp stick welder at its present rpm and I had no problem running multiples of anything. As to what this is cycling at in its present rpm state, I have no clue.