Buying Advice What is the best generator for our needs?

[bigdeano]

I have a 10 kw generator I put together with a US made generator head and a diesel engine. It would start the 3 hp submersible pump I had where I used to live. It was at about 300'. I think it was about at it's limit though, the generator not the engine that is. It won't even budge the motor on my 5 hp air compressor. It has an unloader so it starts easily, but the motor just draws too many amps for the generator. Don't count on anything under 10 kw starting a 3 hp pump unless you try it.

I have a 550 gallon tank of diesel fuel with 300 gallons left that's 12 years old. It still works fine. I made a simple setup to control the airflow in and out of the tank so the air going in goes through a dissicant cylinder to remove the moisture. The tank is above ground.

 

[DarkBlack]

There are two things that the pump must do work to do: Make the water that is sitting still start to move (overcome inertia) and then raise the water. Getting the water moving in the first place is what takes all the power. Once moving, the only "work" the pump must do is to lift it above the static water level.

You are correct. The total depth of the pump matters for starting. There are 2 differnt main loads on the motor in the well. 1) is fighting gravity from the water surface and up. 2) Is accelerating water from a standstill to final speed, and that includes all the water in the pipe, even what is submerged.

 

[DarkBlack]

I just made some measurements again >4 months, and my #'s have come down since the previous #'s were made during almost drought conditions. Not to over emphasise the importance of real measurements for a deep well to work with a genny, but I think people rely on motor labels, then are disapointed. Here a couple more important factors to consider.

Breakers:
You can't even ballpark a startup load by it's breaker. For example, One common breaker curve can hold over 10x it's rating for almost a full second before tripping.

HP rating:
1)The HP rating is a 'typical' rating. If your well depth is deep for that motor, you will draw more current than advertised. For example, my 3/4hp is on the small size for a 275 well, so it draws a lot more at startup than expected.

2)The same HP motor can be bought with a high pressure-low volume pump, or high volume-low pressure. If you have the same HP with a High volume pump version, you will draw more current in a deep well.

3)motor current draw will vary through the year depending on underground water levels.

4) Every checkvalve in the system adds considerably to the initial start load. A one checkvalve system will draw less for that first instance than a system with 3.

5) Pressure tank cut in adds to the load. A switch set for a 30-60psi range will be easier starting than 60-80psi.

I would always measure a deep well pump actually ruunning before sizing a genny.

 

[Turbys_1700]

Here is my 2 cents...
That's about all it's worth anyway...
I am on my 4th generator...
The first two I purchased and then sold...
The third one was stolen...
In about 28 years I have been without power perhaps a dozen times or so...
Typically in the winter months and usually not over a day or two...
I do remember a week outage due to hurricane Hugo in 1989 and a 4 day outage in February due to ice...
For my needs, the last unit I purchased was from Northern Tool on closeout...
It is 7500 W with 10,000 surge...
I run all of my 110 in the house with it and have back up gas logs for heat...
Works well for me and the cost was under 1K...
Every situation is different...
If my power was more problematic then I would need to invest in a more robust system...
For my situation what I have is fine...

 

[radioman]

I think you need to change your approach of thinking on this. I think you need to sit down and look at your energy needs vs wants. If I were you , I would go around the house/other electrical loads outside and write down what you CAN see what you want to run and think what do you really need to live on. Try to think daytime vs nighttime needs. write down the amps or wattage from all devices you want/need and put it in two columns respectively for want and needs of course. I am betting you will be VERY surprised on the numbers you see. chances are it will show the type of person you are or what your family demands when power is out. From there you can size the generator according to your numbers and then think about what fuel you can get in your area or already have if roads are blocked or whatever.

Now- What type of restrictions in CA are you referring to?

 

[BobRip]

I just made some measurements again >4 months, and my #'s have come down since the previous #'s were made during almost drought conditions. Not to over emphasise the importance of real measurements for a deep well to work with a genny, but I think people rely on motor labels, then are disapointed. Here a couple more important factors to consider.

Breakers:
You can't even ballpark a startup load by it's breaker. For example, One common breaker curve can hold over 10x it's rating for almost a full second before tripping.

HP rating:
1)The HP rating is a 'typical' rating. If your well depth is deep for that motor, you will draw more current than advertised. For example, my 3/4hp is on the small size for a 275 well, so it draws a lot more at startup than expected.

2)The same HP motor can be bought with a high pressure-low volume pump, or high volume-low pressure. If you have the same HP with a High volume pump version, you will draw more current in a deep well.

3)motor current draw will vary through the year depending on underground water levels.

4) Every checkvalve in the system adds considerably to the initial start load. A one checkvalve system will draw less for that first instance than a system with 3.

5) Pressure tank cut in adds to the load. A switch set for a 30-60psi range will be easier starting than 60-80psi.

I would always measure a deep well pump actually ruunning before sizing a genny.

These all good points, but the generator specs are unknown. We mostly know what continuous power is, but I have never seen a definition of surge rating. How long can a generator put out this surge. If its one second for example it will not do much for a well pump that takes 30 seconds to reach speed. This is just one point on a curve. We need ratings for 30 seconds, 15 seconds and 3 seconds. Does anyone have a better understanding of this rating?

 

[meburdick]

These all good points, but the generator specs are unknown. We mostly know what continuous power is, but I have never seen a definition of surge rating. How long can a generator put out this surge. If its one second for example it will not do much for a well pump that takes 30 seconds to reach speed. This is just one point on a curve. We need ratings for 30 seconds, 15 seconds and 3 seconds. Does anyone have a better understanding of this rating?

Not sure I understand why the specs are unknown. Just about every generator that I've looked at (shopped out a new one for my home over the last 18 months) showed the continuous and surge load ratings. If memory serves correctly, the surge rating is good for up to one minute at that level before the machine will shut down from overload protection.

 

[radioman]

Thanks everyone! Okay, Hope I answer all of the questions. We were looking for portable type generator for the house. Weather is mild here and our idea was to plug in cords to generator for lamps, hair dryers etc. We really could get by with our camp stove. I have no clue what the fridge watts are but that would be the only major thing (besides well pump). We do not need to run the entire house and turn on overhead lights etc. It does not need to turn on automatically when power goes out. Selected diesel because I read that these generators last longer than gas and we can store the diesel without it going bad. Didn't choose NG in case of major quake and lines go down.
Well pump specs are: 3HP, 1PH, VOLT 230, RPM 3450, AMP 14.5, SF MAX AMP 17.0, and a little blurry but looks like HZ or KZ 60 or 6.0
For house stuff we can really get by with a smaller unit, but it would be nice to have the well work especially if it was an extended outage.
I have looked on CL there was an Apache which I had never heard of but it's gone already...I do like a deal! Thank you

using your max amp times 230volt is roughly less then 4k watts starting up. once its running it will draw about 3300 watts. Getting a gasoline generator with 5000 watts running (not surge) should be able to run your pump. You will need to install a transfer switch and use the 240 volt plug outlet on your generator. you will be able to run a few lights and thats about it. sizing your generator bigger then that will allow you to be more flexible running more stuff at same time.

 

[DarkBlack]

Not sure I understand why the specs are unknown. Just about every generator that I've looked at (shopped out a new one for my home over the last 18 months) showed the continuous and surge load ratings. If memory serves correctly, the surge rating is good for up to one minute at that level before the machine will shut down from overload protection.

I'm not sure on the legal requirements for that rating but I think it is for < 1 second. I think they allow the mfg to count the momontary inertia of the engine+genny to hold approx 60hz before dropping speed.

 

[DarkBlack]

Not sure I understand why the specs are unknown. Just about every generator that I've looked at (shopped out a new one for my home over the last 18 months) showed the continuous and surge load ratings. If memory serves correctly, the surge rating is good for up to one minute at that level before the machine will shut down from overload protection.

I'm not sure on the legal requirements for that rating but I think it is for < 1 second. I think they allow the mfg to count the momontary inertia of the engine+genny to hold approx 60hz before dropping speed.