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  #1  
Old 08-13-2010, 01:56 PM
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Electric generator capacity

I would like to get a pto-driven generator capable of running a well pump and a few lights. What is the minimum generator capacity that will do that job?

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  #2  
Old 08-13-2010, 02:23 PM
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Quote:
Originally Posted by Honus View Post
I would like to get a pto-driven generator capable of running a well pump and a few lights. What is the minimum generator capacity that will do that job?
You would have to ascertain the potential maximum voltage and current draws of the pump and lights, then I would apply a "cushion" factor of at least 100% to get an idea what the minimum output you can get by with first.
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Old 08-13-2010, 02:25 PM
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7500 watts minimum is enough to run the electric water pump, fridge and TV. Just the basics to survive a hurricane.
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Old 08-13-2010, 02:36 PM
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you really need to look at your sump pump and figure out its wattage (normally stamped into a nameplate on the side of the electric motor).

Or, you can usually translate pump HP to wattage (not directly though - motors are not 100% efficient. a 1hp 120v motor needs 16A = 120v * 16A = 1920w or 2kw

http://www.elec-toolbox.com/usefulinfo/flamtrcharts.htm

Add 100w per light bulb, and you should be good -

I'm guessing you'll need a 3 or 5kw generator. a 10K generator is what most people buy to power thier whole house (incl A/C)

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Old 08-13-2010, 03:09 PM
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Agree with above, you need to look at the WELL pump and see what it draws.

I don't have a well pump, but I know from experience they draw big, and probably is 240.

So that will have some bearing on what size generator you need.

I have a 5k (6k peak) unit and can run most of the house. It's a portable generator that I connect up when needed.

No A/c, can't make coffee and use the Nuker at the same time.

I do cycle some of the pumps on and off (We have 2 sumps and 2 ejectors), mainly again so I don't get them all kicking in at once.
Same for friges and freezer.

For a neat trick, I won't go into details if you can't figure it out on your own you shouldn't do it.
Outlets can be inlets, if you have a 240 outlet near where the generator will be you don't need to run extension cords etc.

STEP 1) TURN OFF THE MAIN
STEP 2) TURN OFF THE MAIN
STEP 3) RECHECK THAT YOU DID STEP 1 & 2
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  #6  
Old 08-13-2010, 03:52 PM
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Always get 2-3K above your rated needs.

I wouldn't get less than a 10K unit that can surge to 12K.
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  #7  
Old 08-13-2010, 06:13 PM
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What is you main line coming into your house? If it is a 100amp service a 12k generator will run your whole house. If you are looking for emergency use only there are a couple of ways to go.

If you are handy make up a smaller VITAL breaker box. IE freezers,refers,Beermiester(CLK) heat what ever.

Look at the capacity of the breakers in the box now for them add those up.
Drop a line from the main to the vital box. THIS WILL BE THE NORMAL SUPPLY. Have a second supply line coming into it from your generator EMERGENCY SUPPLY. Use a toggle type breaker(so that only one supply can be in the on position)

It sounds hard but any electricaly minded person should be able to do it in a few hours once the parts have been gathered.
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Old 08-13-2010, 11:45 PM
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I use a 4400 watt generator. It will run everything in my house except the electric water heater and the electric oven. That includes the 1/2 hp 240 V well pump, the tv and computer, the furnace, and a window a/c. More wattage would nice, but I got this generator for a good price and I can rope start it.
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Old 08-14-2010, 12:54 AM
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With all due respect to all the suggestions so far, when it comes to electrical installations if you have to ask how to do it you shouldn't be doing it. If you are going to tie a generator into your grid supplied system you MUST use a transfer switch or you can backfeed the utility line and kill someone!!!! There is also a company that makes an interlock kit for your main panel that will prevent your utility and generator breakers from being on at the same time. It is quite a bit cheaper than a auto or manual transfer switch, but does not work for all panels. Take a look at the amperage on the breaker that goes to your well- probably a 20 or 30 amp 240 volt. If it is a 20 amp you will want a 7500 watt minimum and 10,000 watt if it is a 30 for general rule of thumb. What are you going to run the pto from? A tractor? If so I think you can buy a portable generator in the 7-10K range for a lot less than a pto unit that is more efficient and convenient than running your tractor.
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Old 08-14-2010, 01:01 AM
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I also forgot to mention that if your utility company sees a generator wired into your house without an approved transfer switch or interlock device they will disconnect your service and not reconnect until you have one installed by a licensed electrical contractor.
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Old 08-14-2010, 07:27 AM
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Originally Posted by 10fords View Post
With all due respect to all the suggestions so far, when it comes to electrical installations if you have to ask how to do it you shouldn't be doing it. If you are going to tie a generator into your grid supplied system you MUST use a transfer switch or you can backfeed the utility line and kill someone!!!! There is also a company that makes an interlock kit for your main panel that will prevent your utility and generator breakers from being on at the same time. It is quite a bit cheaper than a auto or manual transfer switch, but does not work for all panels. Take a look at the amperage on the breaker that goes to your well- probably a 20 or 30 amp 240 volt. If it is a 20 amp you will want a 7500 watt minimum and 10,000 watt if it is a 30 for general rule of thumb. What are you going to run the pto from? A tractor? If so I think you can buy a portable generator in the 7-10K range for a lot less than a pto unit that is more efficient and convenient than running your tractor.
Thats why you use a toggle switch. Single pole double throw. That way only ONE source can supply the box.
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  #12  
Old 08-14-2010, 08:02 AM
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Your generator size must be at least large enough to serve all of your running loads AND start your largest motor load.

Since a motor may require 3-6 times its running HP for a few seconds while it starts, this requires a generator that is larger than the sum of your loads.
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Old 08-14-2010, 09:35 AM
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Originally Posted by 10fords View Post
I also forgot to mention that if your utility company sees a generator wired into your house without an approved transfer switch or interlock device they will disconnect your service and not reconnect until you have one installed by a licensed electrical contractor.
This is BS. Lineman have looked at my generator and said nothing.
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Old 08-14-2010, 09:44 AM
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Originally Posted by buffa98 View Post
Thats why you use a toggle switch. Single pole double throw. That way only ONE source can supply the box.
If you use a SPDT switch you are only breaking one leg of a 240V circuit which leaves the other one connected to both sources of power.
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Old 08-14-2010, 09:59 AM
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Originally Posted by Chas H View Post
This is BS. Lineman have looked at my generator and said nothing.
Geez Chas- Everything I post on this forum you come after me with a personal attack. I have no idea how your generator is hooked up, nor do I care. Perhaps you have a local code that allows ignorant people to endanger the lives of utility workers to save a few dollars. I install generators for a living and have done so for the past 25 years so I am quite familiar with the procedure. What do you do for a living?

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