Using a generator to power a water well pump

[TheGoose]

Thanks for your vote of confidence. If you had read the first post, I said it was at least double.

According to Franklin, starting current can be as high as 6 times running current. Luckily, it's only for a moment. Once the motor gets started it should drop down to normal levels.

Also I took the time to list a chart which shows which gensets are recommend (by the manufacturer) to start/run a well pump.

The only thing I see that's wrong is in the first post of the thread.

Starting amperage is THREE times running amperage, not two times. That's standard acceptable practice according to the NEC.

 

[Carl_NH]

Goose,

I think 6x is a bit high. The specs from Franklin and Goulds in the pump manual is below.

Also they state for a 2 wire motor the genset rating should be 50% higher than these #s.

So for a 1 HP it states 4KW then add 50% so 6KW..

 

[MikeInMaine]

Sorry if this point has already been made by others in this thread. If your generator has an "auto idle," "gas saver," or similar feature which slows down the idle when there is no load applied to the generator, you should turn off this feature for motor loads such as a well pump, compressor, etc.

 

[Pilot]

Goose,

Thanks for the posts and your expertise.

I am currently looking into maybe getting a standby generator for the house and the power draw for the well is my biggest concern.

Our well is 110 ft. deep, water is about 60 ft. Pump is a Red Jacket, 1/2 hp, wiring is 10 ga., about 140 ft. long. Well folks urge me to go to 3/4 hp when the pump needs to be replaced--it's 19 years old now.

I now have a 6000W portable generator--there is no peak load rating listed anywhere.

I have a transfer switch.

We run the refrigerator, freezer, furnace fan, some lights, the well and maybe a couple other things I don't remember. No A/C, no stove.

When the well comes on, the lights dim and the generator lugs down for half a second, maybe a little more.

Maybe I'm just being too conservative, but I wonder if that 6KW unit is sufficient for a future 3/4 hp pump while running other stuff. If it isn't, then we'll go ahead with the standby genset, which should let us run more stuff as well.

So, Goose, what do you think?

 

[chopped]

Im curious why they recomend a 3/4 hp? I have had 1/3 hp for yars and no troubles. Reciently when I replaced I went to 1/2 hp and its fine no noticable difference.I was told that a 3/4 was overill . I am at about 114 foot down and maybe 15 foot frok house to well head. number 12 wire..

 

[TheGoose]

Carl,

I'm just quoting what they told me in Franklin pump school. Can't find the document, else I would post it.

2-wire motors usually do require a bit more to start. One reason to consider going 3-wire with a full size (cap start/cap run) C-box.

Goose,

I think 6x is a bit high. The specs from Franklin and Goulds in the pump manual is below.

Also they state for a 2 wire motor the genset rating should be 50% higher than these #s.

So for a 1 HP it states 4KW then add 50% so 6KW..

 

[arrow]

Goose,

Thanks for the posts and your expertise.

I am currently looking into maybe getting a standby generator for the house and the power draw for the well is my biggest concern.

Our well is 110 ft. deep, water is about 60 ft. Pump is a Red Jacket, 1/2 hp, wiring is 10 ga., about 140 ft. long. Well folks urge me to go to 3/4 hp when the pump needs to be replaced--it's 19 years old now.

I now have a 6000W portable generator--there is no peak load rating listed anywhere.

I have a transfer switch.

We run the refrigerator, freezer, furnace fan, some lights, the well and maybe a couple other things I don't remember. No A/C, no stove.

When the well comes on, the lights dim and the generator lugs down for half a second, maybe a little more.

Maybe I'm just being too conservative, but I wonder if that 6KW unit is sufficient for a future 3/4 hp pump while running other stuff. If it isn't, then we'll go ahead with the standby genset, which should let us run more stuff as well.

So, Goose, what do you think?

I have a 1/2 hp pump that is 350' deep. At start up, gen box meter reads a spike to 1750w and then settles down less than a quarter of that. This is with a 5000w 6250 surge generator that is powering the rest of the house (freezer,refer, lights, microwave, coffee pot, hair dryer, flat screen tv and boiler for hot water). It lugs a bit and lights get slightly dim for a very brief time when pump comes on but it is something I can easilty live with as I never have to pay attention about what's running when something else is on. It just plows through no matter what. I even have the throttle adjusted down so I can get 12 hours on a 5 gal tank and still everything just keeps going. First 1/2 hp pump lasted 25 years with a family of 5. Replaced it with another 1/2hp.

 

[TheGoose]

Not a whole lot of difference between a 3/4 and a 1/2 HP pump.

I would think that the 6KW would be plenty of juice. The brand of the generator means just as much as the rated amperage.

Goose,

Thanks for the posts and your expertise.

I am currently looking into maybe getting a standby generator for the house and the power draw for the well is my biggest concern.

Our well is 110 ft. deep, water is about 60 ft. Pump is a Red Jacket, 1/2 hp, wiring is 10 ga., about 140 ft. long. Well folks urge me to go to 3/4 hp when the pump needs to be replaced--it's 19 years old now.

I now have a 6000W portable generator--there is no peak load rating listed anywhere.

I have a transfer switch.

We run the refrigerator, freezer, furnace fan, some lights, the well and maybe a couple other things I don't remember. No A/C, no stove.

When the well comes on, the lights dim and the generator lugs down for half a second, maybe a little more.

Maybe I'm just being too conservative, but I wonder if that 6KW unit is sufficient for a future 3/4 hp pump while running other stuff. If it isn't, then we'll go ahead with the standby genset, which should let us run more stuff as well.

So, Goose, what do you think?

 

[BobRip]

I have a 1/2 hp pump that is 350' deep. At start up, gen box meter reads a spike to 1750w and then settles down less than a quarter of that. This is with a 5000w 6250 surge generator that is powering the rest of the house (freezer,refer, lights, microwave, coffee pot, hair dryer, flat screen tv and boiler for hot water). It lugs a bit and lights get slightly dim for a very brief time when pump comes on but it is something I can easilty live with as I never have to pay attention about what's running when something else is on. It just plows through no matter what. I even have the throttle adjusted down so I can get 12 hours on a 5 gal tank and still everything just keeps going. First 1/2 hp pump lasted 25 years with a family of 5. Replaced it with another 1/2hp.

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?

 

[TheGoose]

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.

 

[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.