How much Generator for a well pump??

[BobRip]

Without basic information, there's no way to respond. Is the well pump 110v or 220v, and what is its' amp draw (one can add at least a 1/3 more for the start-up load)? I've a 3500watt Honda, and it can handle 1 of my 2 well pumps, the one purposefully kept to 1/2 HP, 110 v and 12 amps (specifies 12 running, 20 start). That pump goes to my garage/apartment, and for modest irrigation. The other well has a 1HP pump at 220 volts and 15 amps (running), and the circuit breaker on the 3500watt generator trips when connected to that circuit --- so I need to bring in my 6500watt Honda to handle that one (which, when I ever get it built, will be for my main house) - but, since I'm not interested in timing the on-off cycles of the various electrical draws in my house (e.g., can't run well pump at same time as 2 refrigerators, a microwave, lights and so on), I'll upgrade to a 15KW built-in and propane powered unit when I move in.

To help with this, buy a large surge tank, 40 gallons or so, and it will supply your with water for several hours between runs. Then you cut everything off for 3 minutes, charge up the tank and go. The issue with a large generator is fuel consumption. Even lightly loaded the 15 KW generator will use more than 1 gallon of gas an hour. That's 24 gallons a day, or at least 12 if you run it half time. You need to run 12 hours to keep the refrigerator cold. How much gasoline can you store? With trees down, can you get to the gas station? Will it have power? I believe you should have at least 3 days and more like a week's worth of survival power available. Find a way to get gasoline out of your car gas tank. Store gasoline with Stabil. Keep spare oil, filters, and spark plugs. You cannot find these in a power outage even if you get to the store. You are not trying to live a life of luxury, but you do not know how to live in the stone ages and you need to at least have water, refrigation, lights, and a radio. With out these things get pretty bad.
The 15 KW generator will use up all your gas so quickly that you will have nothing in short order. Just one man's opinion.

Propane has advantages, but when you run out somebody has deliver it. If you go this way get at least a 1000 gallon tank. Don't let it get below half full.

 

[ByronBob]

I asked this same question to my well guy. Told him I was getting a 5250 watt generator with a 30 amp plug. He said well the pump only uses 6 amps so heck yea that's fine.

You'd be suprised at what a 5000 watt generator will power in your house. The trick is to turn the switches on 1 at a time to get over the surge loads...

 

[Dusty]

To help with this, buy a large surge tank, 40 gallons or so, and it will supply your with water for several hours between runs. Then you cut everything off for 3 minutes, charge up the tank and go. The issue with a large generator is fuel consumption. Even lightly loaded the 15 KW generator will use more than 1 gallon of gas an hour. That's 24 gallons a day, or at least 12 if you run it half time. You need to run 12 hours to keep the refrigerator cold. How much gasoline can you store? With trees down, can you get to the gas station? Will it have power? I believe you should have at least 3 days and more like a week's worth of survival power available. Find a way to get gasoline out of your car gas tank. Store gasoline with Stabil. Keep spare oil, filters, and spark plugs. You cannot find these in a power outage even if you get to the store. You are not trying to live a life of luxury, but you do not know how to live in the stone ages and you need to at least have water, refrigation, lights, and a radio. With out these things get pretty bad.
The 15 KW generator will use up all your gas so quickly that you will have nothing in short order. Just one man's opinion.

Propane has advantages, but when you run out somebody has deliver it. If you go this way get at least a 1000 gallon tank. Don't let it get below half full.

A 1000 gallon tank is overkill for most residences. Propane in New England is costing about $2.75 - $3.00 per gallon. That would be a sizable investment for any homeowner. The 1000 gallon tank is also quite large.. 41" diameter X 194" long. Also, a 1000 gallon tank holds 800 gallons of propane, not 1000, so the cost factor will be a little less, but still substantial. I would believe that a 500 gallon tank would be adequate for most outages, unless they were like Katrina. Then, no amount will be enough. If I were buying a 15KW generator, I would only consider a 1800 RPM diesel. It probably wouldn't cost any more than a propane generator, and the operating costs wouldn't be nearly as expensive.

 

[BobRip]

I asked this same question to my well guy. Told him I was getting a 5250 watt generator with a 30 amp plug. He said well the pump only uses 6 amps so heck yea that's fine.

You'd be suprised at what a 5000 watt generator will power in your house. The trick is to turn the switches on 1 at a time to get over the surge loads...

If you only pull 6 amps, you will probably be OK with a 5250 continuous output. Make sure that's not surge.
You might ask the store to guarantee the generator will start your well pump. Sorry to be so picky, but I ended up with a larger genrator and then still had to rewire my well during Isabel. The well was 300 feet deep. I gather yours is much shallower. After rewiring, the 5000 watt generator starts my well and it pulls about 11 amps when running.

 

[DrewL]

simple..................... volts times amps =watts

 

[thingy]

Than multiply that by 3 [or more it seems],,and you get the start up watts needed,,,,anything with an electric motor[refride/freezer/pump,,etc],,takes a lot more to start up,,,thats why its so confusing,,,,if you got a smaller type gen,6-7,000 watts,,you better turn breaker off for freezer and refidge,,that is if you got a water pump,,just use what you need,,furnace[gas or oil],,water pump,,a few light bulbs,,maybe tv,,and phone too,,,,other wise, you are going to burn up motors,,,if you had to,,you could alternate things,,,thingy

 

[BobRip]

Than multiply that by 3 [or more it seems],,and you get the start up watts needed,,,,anything with an electric motor[refride/freezer/pump,,etc],,takes a lot more to start up,,,thats why its so confusing,,,,if you got a smaller type gen,6-7,000 watts,,you better turn breaker off for freezer and refidge,,that is if you got a water pump,,just use what you need,,furnace[gas or oil],,water pump,,a few light bulbs,,maybe tv,,and phone too,,,,other wise, you are going to burn up motors,,,if you had to,,you could alternate things,,,thingy

I agree with thingy. The well has to acclerate the water in the pipe going to the house. This acts like a flywheel and the startup current continues much longer that it would for a refrigator or most other motorized loads. Of course you can try it and see, but be prepared to trip the well breaker if the lights stay dim to long.

 

[thingy]

Yeah,its not exact I think on them water pumps,,,seems like mine was about 5 amps,,with 220/230 volts,got it replaced not long ago,been there for about 16 years I think,,[about 800 dollars],[1/2 h.p,,100 foot deep],,,,so that would come to 1,000-1,200 WATTS,,,3 times that would be 3-3,600 watts,,,,,got a 6,500 wattt[surge gen],6,000 watt running,,,,the lights dimed for a 1/2 second,,,and at the most I was using was maybe 1,000 watts additional,[few lights,tv,,,dish reciever,phone],,,no refedge or any thing else had breaker on,,,furnace wasn't even running,,,so,it seems them water pumps use alot,,,not no electrician,,,,I also imagine it applys to other motors as well,although probably to a lesser degree,,[meaning one may be different than others,given amps and volts on plate on motor were the same??],,thingy

 

[Highbeam]

It's even worse. The typical pump like thingy has is 1/2 HP which EQUALS 375 watts. I have no idea why a pump rated as 1/2 HP would need even 1000 watts after the initial surge is overcome but as Thingy reports, it does.

All electric motors have that surge when going from a locked rotor to full rotational speed. Once there though, the rating of the motor in HP or watts should be all it takes.

All this means that there is no logical way to know what you need for input power unless you(or a trustworthy buddy) have run the same pump under the same conditions.

 

[midlf]

With alternating current you cannot multiply voltsXamps to get the watts. You get voltamps, VA. The watts are always less than the VA for a motor. It has to do with the phase angle between the voltage wave and the current wave. A pure Resistance load, such as a heater or light bulb has zero phase angle between the voltage and current. For an inductive load the current lags behind the voltage. This is referred to as power factor. Industrial loads get penalized for poor power factor. Knowing the phase angles, power factors, the watts and the vars (the reactive part of the power system) is the major part of running a utility power system. All transformers and large generators are rated in VA (or kVA or mVA). The little ones also but the mfrs do not get into it because it is so confusing so they just call it watts. This is why thingys pump calculates out to 1000 watts when 1/2 hp is less than that. What he really has is a 1000VA load. If you try and use the watts equivalent of HP to size your generator you will be in trouble. As stated by all you also have to figure on the inrush starting surge. The surge watts listed on some generators is just the inertia factor of the rotating mass. The less mass the faster this goes away. And with a cheap generator I bet it goes away fast.