# Well pump power consumption



## Pete Q

I have been wondering about the power consumption of my well pump. Unfortunately I have no idea about the wattage of the unit. In the case there is someone here who could make an educated guess about it, here is what I know about the well: It is 350' deep, 5" casing, and the pump has a 20A/240V dedicated breaker. When I stand by my pressure tanks I can hear when the pump goes on and off, so what I am planning on doing is to just time the on-off times of the pump during various times of the day and water-consuming activities on the property. Just need to have understanding about how much power does the pump draw when it is on.

Pete


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## oldasrocks

Our well is 360 ft to the pump. 2 hp pump. The electric company says it would cost us 2 dollars a day to run it for 24 hrs. You should be able to figure out the hp by looking at the control box. Call your electric company for info.


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## Pete Q

oldasrocks said:


> Our well is 360 ft to the pump. 2 hp pump. The electric company says it would cost us 2 dollars a day to run it for 24 hrs. You should be able to figure out the hp by looking at the control box. Call your electric company for info.


Thanks for the quick response. I am additionally trying to figure out the maximum surge I need to cover when the pump starts. If I understand these calculations correctly, 2 HP equals about 1500 W, hence in a 240 V circuit a 2 hp motor would pull up to 6.25 A. Is this the definite maximum surge then, presuming that after the pump has started it draws considerably lower amperage?


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## fishhead

I think those would be running amps not start-up.

Also, I'm pretty sure that 2 hp will draw more than 6.25 running amps at 220 V. An electrical engineer friend said that 746 watt/hp is theoretical not actual draw.


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## Pete Q

fishhead said:


> I think those would be running amps not start-up.
> 
> Also, I'm pretty sure that 2 hp will draw more than 6.25 running amps at 220 V. An electrical engineer friend said that 746 watt/hp is theoretical not actual draw.


I think you are correct. Just went to see a random 2 hp well pump motor specs in Grainger web site, and they list 9.6 A max load with 230 V and 19.2 A with 115 V. Is the max load same as the startup surge load? I have heard some comments that it could be as high as 25A with a 2 hp pump, but I don't understand how that would be possible without tripping the breaker of a 20A/230V circuit.

To give a little more background, the two main reasons why I am looking into this is that I want to understand short term what kind of backup generator I will need to run the pump, and long term what kind of dedicated solar system would it take to run the pump on a regular basis. The well and the pressure tanks are about 300 feet from my main house, which is why I am looking for a dedicated power system and dedicated backup power for the water.


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## TnAndy

Most likely the 9.6amps is full load current. My little Square D slide card calculator calls for 12a on a 2hp motor, but that would be a free standing motor, not one submerged in 50-55 degree water all the time. The start up current, you can figure is a very brief spike of somewhat under your breaker, or you are correct, it would trip most of the time. What you would have to do is size your inverter to handle that surge.

For example....say 10a ( just to make figuring easier ) time 240v is 2400watts continuous. Meaning the very MINIMUM your inverter could be is about a 3000w.....and it must be able to handle a motor starting, probably up to 3500w. You need to check very carefully when you buy your inverter that is will handle a 2hp motor starting. AND you will need an inverter that will produce 240v.....most are 120v.

I have a pair of Outback 2500w on my system that does do 240v, for a total of 5,000 watts. That would certainly handle your pump.....but you realize you are looking at about $4000 ( with the Mate that makes the 'master/slave' arrangement that lets 2-120v inverters produce true 240v AC )

You're also looking at a pretty fair battery bank ( probably 400amp/hrs or better ), and something in the neighborhood of 1200-1500watts of panels.

You're gonna have $15,000 ( or more ) tied up in this water pumping backup system, you know....

An alternative suggestion:

Do you have any way to elevate a tank to provide gravity feed pressure....30-40' is the about the bare minimum IF you want pressure. An alternative to that would be a ground level ( or even buried ) tank, say 1000 to 1500 gallons and a small DC pump to pressure feed your water ( don't know how much you require daily ).

IF you went with one of the above, you could put in a Grundfos SQ series pump...see this website for info

http://store.solar-electric.com/grsqpu.html

These pumps will run on AC or DC. You buy the pump ( say $2,000)....the control box ($500).....a generator interface ....($600).....and you have maybe $4,000 in the whole deal including the labor to pull your existing pump and install this one.

Grid goes down....you can run it off your generator.

Grid stays down.....you can run it directly off DC ( THAT is the beauty of this deal.....you cut out the batteries, the inverters, the charge controllers, etc ) by putting a MUCH smaller array of panels up ( say 4-500watts versus 12-1500 to run your current pump)....the pump on DC will pump a lot less volume....BUT it pumps it continuously as long as the sun shines on your panels ( hence you need a storage tank ).

SO, instead of an expensive, dedicated ( including batteries to maintain ) solar power system to run a hog of an AC pump....you now have an AC pump for when the grid or your generator supplies AC, and a DC pump when solar takes over.....$4k versus $15k.....you can put the other $9k of solar to work doing other things for you...not sitting around waiting to run a water pump.

Food for thought.


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## byexample

To approximate the start-up surge of a motor that size I generally multiply the running draw by 2 to 4 times... depending on the drag on the motor. Being that deep, I would fully expect that your well pump draws 4 times the running current for a brief moment during start-up. The reason your breakers don't trip is because the surge doesn't last long enough to produce enough heat to trip the breaker.

If you want to pump water with solar, it will ultimately be far less expensive to replace your well pump with something designed to run off solar.

I'd estimate that it will cost about $40,000 (minimum) for a solar power system big enough to run that well pump. You will require a fairly large inverter to be able to accommodate that well pump. The inverter will have to be sized to the estimated surge. 

In contrast you could install a $2500 Grundfos pump & controller with 4 dedicated solar panels for an approximate total of $5000 - $6000. Add some batteries and you could still be under $10,000 total.

With a 5" casing you should, in theory, be able to keep your existing 240V pump and install a solar pump above the existing pump. Then you would have 2 water pumping solutions.

I strongly recommend against trying to use the existing pump via an off-grid power system unless you are seriously swimming in money.

Best of luck!


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## Txrider

byexample said:


> To approximate the start-up surge of a motor that size I generally multiply the running draw by 2 to 4 times... depending on the drag on the motor. Being that deep, I would fully expect that your well pump draws 4 times the running current for a brief moment during start-up. The reason your breakers don't trip is because the surge doesn't last long enough to produce enough heat to trip the breaker.
> 
> If you want to pump water with solar, it will ultimately be far less expensive to replace your well pump with something designed to run off solar.
> 
> I'd estimate that it will cost about $40,000 (minimum) for a solar power system big enough to run that well pump. You will require a fairly large inverter to be able to accommodate that well pump. The inverter will have to be sized to the estimated surge.
> 
> In contrast you could install a $2500 Grundfos pump & controller with 4 dedicated solar panels for an approximate total of $5000 - $6000. Add some batteries and you could still be under $10,000 total.
> 
> With a 5" casing you should, in theory, be able to keep your existing 240V pump and install a solar pump above the existing pump. Then you would have 2 water pumping solutions.
> 
> I strongly recommend against trying to use the existing pump via an off-grid power system unless you are seriously swimming in money.
> 
> Best of luck!


That sounds sensible. 

I wouldn't try to run the existing well off solar without matching the breaker rating in solar power. 20A/240V is about 5KV, and you would need over a 5KV rated system to actually get 5KV, a 10KV rated system would be best. A 10KV generator as well. Otherwise you may well burn up your pump.

Best to get a system designed for solar.

I also haven't seen the rated HP of the pump in question stated.


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## davel745

Just guessing. It might use 4000 W at startup and may use about 1100 to 1300 watts running. Maybe less. 

That is about what ours uses. 

Dave


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## KeithBC

I run my 1/2 hp well pump off a 6000W generator (It will handle a momentary 8000W surge, according to the manual.). It works fine. The lights flicker slightly when the pump cuts in, but the governor is able to throttle the generator within less than 1/4 second.

As others have said, you probably want something different for a solar system.


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## artificer

Where did the 2hp come from? I saw it in Oldasrocks post, but it didn't look like Pete said that is what his pump is.

We have a 10gpm Flotec 3/4hp pump. It draws about 8amps running on 220v. Thats 1760 watts. I believe the hp is pump hp, not the electrical.

Post the make/model of the pump, and we can tell more about your system.

Michael


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## Pete Q

Thanks for all the constructive answers. I would be happy to know myself what the make, model, and other specs of my pump are, but I have no idea how to tell as long as it is in the well 350 feet deep. All I know is the breaker size in my service panel and the depth of my well, and the guesstimate 2 hp came from the fact that many 2 hp pumps require the 20A/240V breaker that I have, as well as from knowing that it takes a good size pump to operate in 350' deep well.

From the many comments related to a solar system, it is obvious that it will remain a "long term" plan - meaning that maybe ten years from now the solar technology will have improved enough to allow for something with a reasonable cost. In the meanwhile I will be buying another generator to operate the well pump during power outages, as the distance at least would make it very difficult to operate just one generator for the well and the house.

Thanks again to all helping me to figure this out.


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## Pete Q

artificer said:


> Where did the 2hp come from? I saw it in Oldasrocks post, but it didn't look like Pete said that is what his pump is.
> 
> We have a 10gpm Flotec 3/4hp pump. It draws about 8amps running on 220v. Thats 1760 watts. I believe the hp is pump hp, not the electrical.
> 
> Post the make/model of the pump, and we can tell more about your system.


It appears also Flotec lists 2 hp pump for over 300' lift.
http://www.flotecpump.com/pdf/Pg_43_2006.pdf

I would be happy to post the exact make/mode of the pump if I knew how to read it from the pump that is in the well. Is it supposed to be marked somewhere above the ground as well? Maybe you can advise me with that. Thank you.


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## Guest

Around here, all the information original to the well and pump installation is on a plate(usually a piece of stamped sheet metal) attached to the well casing. If your pump has been replaced by a homeowner, that information may not be current. Rules may be different is other states.


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## Pete Q

zong said:


> Around here, all the information original to the well and pump installation is on a plate(usually a piece of stamped sheet metal) attached to the well casing. If your pump has been replaced by a homeowner, that information may not be current. Rules may be different is other states.


Unfortunately nothing about the pump in the plate.


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## Jim-mi

Do plenty of homework before buying a genny.
What will the genny handle for 'surge'...........??

From what is described you are going to need a hefty gen....

Do Not buy one of those 2-3-400 buck cheapies . . .you will be looking for grief if you do...........

Another way to go . . .Change out the existing pump -now- for a Grundfus and then you will know that 'it' can be run by a Honda of 5000 watts or less. . . . . And . .down the line it can be run by solar power . .as you can afford it.


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## Pete Q

Jim-mi said:


> Do plenty of homework before buying a genny.
> What will the genny handle for 'surge'...........??
> 
> From what is described you are going to need a hefty gen....
> 
> Do Not buy one of those 2-3-400 buck cheapies . . .you will be looking for grief if you do...........
> 
> Another way to go . . .Change out the existing pump -now- for a Grundfus and then you will know that 'it' can be run by a Honda of 5000 watts or less. . . . . And . .down the line it can be run by solar power . .as you can afford it.


At this point I don't have much problem spending a bit over $1000 for a good size generator. After all, right now we have zero access to any sort of water during a power outage. While I agree I don't want to buy something that does not start when it needs to, but still this one would not be for 24/7 use but just to run maybe 30-60 minutes 1-2 times a day during power outage, which happens max 1-2 times a year these days. For what I can tell from Amazon offerings it looks like $1200 would get me a cheap 8 kW (10 kW surge) unit. Something like this:
http://www.amazon.com/Generac-5680-...?ie=UTF8&s=home-garden&qid=1278261032&sr=1-13

The specs say it runs 11 hours with a tank full at 50% load (8 gal). I

While I am contemplating all this I'm still open for other ideas and suggestions for guaranteeing my potable water supply with less than $2000 investment.


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## artificer

The first thing you need to do is buy a cheap clamp on current meter. $10-$20, and it will tell you what the actual current draw is. Another idea is to find out the flow from the pump. Get a 5 gallon bucket and stopwatch. Use the faucet/hose bib closest to the well/pump. Time how long it takes to fill the bucket. (size of container in gallons) * 60 / (time in seconds) = gpm

As I've said, we have a 3/4hp flotec pump. It is supposed to get a 25amp breaker. The flotec 1/2hp pumps need the 20 amp breaker.

Just because your well is 300 feet deep, that doesn't mean the pump is that deep. Our well is 297' deep, but water is at 115'. Pump is at 200', but it only has to pump up the 115', or whatever the level is now. You can measure the depth to the water by using a piece of twine and a closed bell. You could probably use one of the small decorative cow bells that have an opening about 1 1/4" across. It needs to be air tight. You tie the twine on the handle, and lower it down the well. When it hits the surface, it makes a pock sound. Raise and lower it to hear the pock, pock, pock. Its surprisingly audible even from a deep well. (as long as there isn't much noise at the top of the well.)

We use a 4000watt Onan RV generator to power the pump for now. It doesn't have any problem, since its only running at half load with the pump. 10,000 watts is massive overkill, in my opinion. If you only have a 20 amp breaker powering the well, thats only 4,400 watts max. If your breaker doesn't trip, its probably only around 3,500 watts. You really need the clamp on current meter... 

Michael


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## Jim-mi

The problem here is the -unknown- factors.
Well drillers have a track record of putting in BIG pumps.
Part of that is profit margins . . .Big pump . . .big bucks.
Also Big pump . . .guarantee customer "lots of water"

Well drillers motto: . . .Bigger is better . . . .

So . .untill you can electrically prove otherwise . . .that 10,000 watt surge ability is not overkill. 

It is far better to provide the electrical "start up needs" of that pump, than damage the pump and controller because of a "too small" supply..................


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## FarmerGreen

I think these pumps can work down to 390'. This is a hand pump with a optional DC motor that can run off 1 or 2 130v solar panels. I'm getting one soon and will be using it with a 1400 gallon tank about 30' above the house. That way most of the water pressure will come from gravity. 

http://www.simplepump.com/OUR-PUMPS/Motorized.html


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## Txrider

Jim-mi said:


> The problem here is the -unknown- factors.
> Well drillers have a track record of putting in BIG pumps.
> Part of that is profit margins . . .Big pump . . .big bucks.
> Also Big pump . . .guarantee customer "lots of water"
> 
> Well drillers motto: . . .Bigger is better . . . .
> 
> So . .untill you can electrically prove otherwise . . .that 10,000 watt surge ability is not overkill.
> 
> It is far better to provide the electrical "start up needs" of that pump, than damage the pump and controller because of a "too small" supply..................


That's my thoughts, it could even be a 5hp pump.


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## Qhorseman

Went with a PV direct system from the very start, my controller has the option of using a grid or generator source as a back up, never had to use it. Have a 500 gallon tank in a room behind the shed with a 12 volt shur-flo to supply household water pressure. I bought the system as a package, I supplied the retailer with my well depth and water depth, they sent the pump I needed, the price was comparable to a grid powered pump system. I bought the drop pipe and pump wire locally.


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## Rick

Friends...the GRUMPY FACE was added in error!!!




Pete Q said:


> At this point I don't have much problem spending a bit over $1000 for a good size generator. After all, right now we have zero access to any sort of water during a power outage. While I agree I don't want to buy something that does not start when it needs to, but still this one would not be for 24/7 use but just to run maybe 30-60 minutes 1-2 times a day during power outage, which happens max 1-2 times a year these days. For what I can tell from Amazon offerings it looks like $1200 would get me a cheap 8 kW (10 kW surge) unit. Something like this:
> The specs say it runs 11 hours wi...change your stored water less often that way.


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## Paul in VA

I'm interested in being able to run my well pump for brief periods during power outages using a bank of 12v batteries and an inverter. I have 15 surplus 12v Hawker SBS 60 batteries (60 aH new, probably less than that now), which I keep charged. My well pump runs on a 220v circuit and has a 20 amp breaker - I don't have the specs for it.

I'm looking at a Chinese made inverter - output 10,000/5,000 watts, 220v ac, 60 hz - the web link is listed at the end of this post. Based on what's been posted here, I would think this would work, but would like to hear some other opinions.

Thanks

Here's the link for the inverter:

http://cgi.ebay.com/10000w-MAX-5000...s=63&clkid=5376025769216227355#ht_4263wt_1141


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## Jim-mi

Those units have NO track record........
Might as well buy 2 or 3 of them so that when you release the can of smoke on one . .then you have a back up or two............
when one goes poooffff are you going to send it back to Hong by the Kong . . ???

Perhaps you can tell that I have a very low opinion of that china junk.....all the more so in this case because you talk of using that unit for a very important item in life . .Water.

In the very least I would use a Xantrex TR series inverter.
If there is a problem, you have recourse here state side..........


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## Pete Q

artificer said:


> The first thing you need to do is buy a cheap clamp on current meter. $10-$20, and it will tell you what the actual current draw is.


OK It took me a "little" while but I finally got a clamp meter in my hands. Now I'm confused. The pump is hard wired to a 20A/240V breaker. How do I measure the current draw? The meter is showing just zero when I clamp it around the cable so I understand I need to somehow separate the wires within the cable to measure the current. What is the easiest safe way of doing it in this kind of situation, of is there any?


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## Pete Q

Rick said:


> How much potable water do you need. If had the weatherproof storage I would store 50 or more gallons in 7 gallon containers for whatever. Culligan told me if sealed fresh water would remain bacteria free for at least 30 days. Just rotate your stock regularly.


Obviously this would work, but I can't see I would have time, energy, and memory to go through the filling and emptying exercise every month. Thanks for the idea though.


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## idahodave

The clamp on ampmeter should be on one wire....if you take the cover off the breaker panel you should find two wires connected to the pump circuit breaker. Put the meter around one of them.

I think the generator is the best solution. Get a transfer switch for the pump to make it easier to use. 

If you have space, add pressurized water storage. A couple of large tanks could last for a day if you're careful. The tanks would also help the pump last longer by minimizing on/off cycles when there's power available.


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## Pete Q

idahodave said:


> The clamp on ampmeter should be on one wire....if you take the cover off the breaker panel you should find two wires connected to the pump circuit breaker. Put the meter around one of them.


Of course! I should have thought about this.



idahodave said:


> I think the generator is the best solution. Get a transfer switch for the pump to make it easier to use.


I came to the same conclusion. I already have an old "farm style" up to 100 amp generator receptacle and transfer switch in my main power pole. Now I just need to understand if my old 3.5 kW generator is powerful enough to handle the pump start surge. I also called the company that drilled my well and installed the pump for the original owners 1981. They would not have any records about the pump any more, but said that the surge is no higher than 8 amps. I still want to measure to be sure, since it sounds suspiciously low to me. I certainly hope that 8 amps (2 kW at 240V) is correct, since in that case I already have everything I need.



idahodave said:


> If you have space, add pressurized water storage. A couple of large tanks could last for a day if you're careful. The tanks would also help the pump last longer by minimizing on/off cycles when there's power available.


For long term my thinking still is about PV panel and a low current pump in for the well combined with a larger tank on the surface, but for various reasons this major redo of my water system is still some years away, so I just need a backup solution for our water supply during power outages for the next 3-5 years.

Thanks for great advice.


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## Pete Q

So I successfully used my new clamp meter and it showed about 12 amps when the pump was running. However, against the expectations it did not show any kind of start surge. Is it possible that the surge is so fast that it does not show on the meter like this? So, should I now presume that the pump's continuous current draw is 12 amps and the surge could be about double that. This would mean that my generator surge power requirement would be about 5700 W? I have been warned by several people that an using the under powered generator will burn the pump really fast, so I don't really feel like experimenting with it too much. Needless to say that the well company that installed the pump long time ago gave me wrong information when I asked last week.


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## idahodave

If it's a digital meter it doesn't respond quickly enough to show the startup surge. I used a old analog meter to watch the startup of some big fans and it just peaked and fell back down to run level in a second or so.

One thing about the pump motor is the lines that supply it are fairly long and provide a litle resistance to limit the startup current. I don't think the 3500 watt generator has enough capacity for the pump, but the one in a previous post with 10kw surge would.


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## Energy Rebel

Pete Q said:


> So I successfully used my new clamp meter and it showed about 12 amps when the pump was running. However, against the expectations it did not show any kind of start surge. Is it possible that the surge is so fast that it does not show on the meter like this? So, should I now presume that the pump's continuous current draw is 12 amps and the surge could be about double that. This would mean that my generator surge power requirement would be about 5700 W? I have been warned by several people that an using the under powered generator will burn the pump really fast, so I don't really feel like experimenting with it too much. Needless to say that the well company that installed the pump long time ago gave me wrong information when I asked last week.


Pete, you can usually figure 150% of the running amps for the momentary surge on start up.
You may run across an occasional motor that pulls double, but when you size breakers for motors that is the figure that NEC uses (Nat'l Elec. Code).
That's the reason your breaker never trips.


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