Buying Advice What is the best generator for our needs?

[BobRip]

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.

That is the first I have heard of the one minute. So what is the 30 second, 15, and 3 second ratings? Can you run the generator at the 3 second surge rating for 3 seconds and then you must go back to below the continuous rating. These are unknowns. Also I wonder if all generator manufacturers use the same testing method. If not then it may not be possible to compare generators from different manufacturers.

 

[DarkBlack]

I have the engine manufacture's torque+HP graph on my 5000/6250. Here's where it gets interesting:
The engine is rated 10HP...But that's at 4k rpms. The genny must run down at 3600rpms. At this speed the engine produces 9HP, not one bit more.
9HP=6714 engine shaft watts best available. Now...
Typical generator head is ballpark 80 efficient. 6714 * 0.8 =5,371 watts. So it is clear that only momentary physical inirtia would allow this unit to make the advertised 6250 'surge' watts.

 

[Carl_NH]

BobRip,

From my own experience and also the earlier posting on the pump start current graph the surge of amperage indicates between .2 seconds and .5 seconds (half a second) - what motor draws a starting load for 30 seconds?

I just did maintenance yesterday on my well, filters and tank charge pressure and checked the amperage draw using an amprobe manual meter and the surge was less than 1 second at 22-23 amps then settled in at 10 amps running current. (its a 1.5 HP 10GS15 Goulds pump with 2 wire Franklin motor)

The Franklin sumersible motor guide for generator sizing to HP indicates a 1.5HP needs a minimum of 5KW rating plus if its a two wire motor 50% higher so at least a generator with 7.5KW surge rating is the way I read this for a two wire motor starting system.

The 3 HP the OP has is a 14 AMP running 3 wire motor and per the same graph this requires a 10KW generator to run but not 50% over due to the three wire has the starting controls and capacitor setup.

 

[jenkinsph]

Earlier in the thread I suggested a 3kw Honda reading thru the thread again I still think that is the best way to go. MOST people can use a small genset with about 10 gallons of gas and get by. This fuel can easily be rotated thru their cars, light trucks, boat and lawn mowers. I recommend using Stabil in the fuel to increase the storage time but would keep it rotated a few times a year anyway. A person who is willing to go to the trouble to keep fuel rotated and fresh may have a little more fuel on hand.

Sizing the genset to the water pump, seems everyone wants the rest to know what they know about load calculation. While there isn't anything wrong with that I hardly think it applies to the OP with a $1500 to $2000 budget proposal. As a fully licensed electrician myself the costs for hardwiring in a system in the OP's locale may be over the budget allotment. FORGET THE WATER PUMP IF IT IS 3HP. Use bottled water for drinking and a storage tank to flush the toilet with a bucket. That sure bears not having a toilet at all.

Lots of people have an rv and if you do keep the batteries charged up so that it can aid you in getting thru the power outage. Plug in the refrigerators and freezers with a good quality extension cord. Might want to plug in your tv or a radio . to get the news about what is going on. You can power a microwave, coffee pot and other small appliances as needed but try to be FRUGAL.

Now if you are a person who is so soft that you have to have everything during a power outage including hair driers, couple of hvac systems, deep well pump, electric range then dig deep in your pockets and hire a professional to set you up a larger system hardwired in with storage tank. But it will be alot more than $1500.

 

[BobRip]

BobRip,

From my own experience and also the earlier posting on the pump start current graph the surge of amperage indicates between .2 seconds and .5 seconds (half a second) - what motor draws a starting load for 30 seconds?

I just did maintenance yesterday on my well, filters and tank charge pressure and checked the amperage draw using an amprobe manual meter and the surge was less than 1 second at 22-23 amps then settled in at 10 amps running current. (its a 1.5 HP 10GS15 Goulds pump with 2 wire Franklin motor)

The Franklin sumersible motor guide for generator sizing to HP indicates a 1.5HP needs a minimum of 5KW rating plus if its a two wire motor 50% higher so at least a generator with 7.5KW surge rating is the way I read this for a two wire motor starting system.

The 3 HP the OP has is a 14 AMP running 3 wire motor and per the same graph this requires a 10KW generator to run but not 50% over due to the three wire has the starting controls and capacitor setup.

My well pump takes about 30 seconds to settle down to rated motor current.

 

[dave1949]

I think home generator choices/needs will vary considerably by location and situation. In areas with hard winters for example, an adequate generator can save a house from freezing up, repairing that can get expensive in a hurry. A generator is not the only way to avoid that, but it is a valid way for some to be prepared. For people who rely on pellet stoves or inserts with fans as alternate heat sources, a generator makes a lot of sense.

Keeping a frig or freezer running can be important if their contents are expensive. Well power can be critical to those with livestock.

I am amazed by the number of rural residents who don't put much thought into what they would need if power goes out for an extended time. Every big outage kicks off another local generator scramble it seems.

Maybe one alternative to a generator for those on wells that aren't too deep, is adding a hand pump. There are some that are (advertised to be) freeze-proof and can share the well casing with the regular piping. Bison Hand Water Pumps Lot of work, but never runs out of gas :laughing:

 

[DarkBlack]

My well pump takes about 30 seconds to settle down to rated motor current.

My 1hp pump used to do that-then it finally never came out of it. At the very end It was actually cyling it's own thermal switch, and not the pressure switch on the tank.

 

[BobRip]

My 1hp pump used to do that-then it finally never came out of it. At the very end It was actually cyling it's own thermal switch, and not the pressure switch on the tank.

I have not looked at the current since I increased the wire size. I will see if I can do this.

 

[BobRip]

My 1hp pump used to do that-then it finally never came out of it. At the very end It was actually cyling it's own thermal switch, and not the pressure switch on the tank.

Ok, I tested the pump current. Remember I have upgraded the 300 feet of wire in the well from 12 guage to 10 guage since I last took readings. I also put in a new pump at the same time. The current has changed. The peak current using the max function on the meter was 27 amps. It lasted almost no time. The next reading was 8.7 amps. On another test not using the max function I got 20 amps max. It looks like the slow startup was due to the smaller wire, as we had determined. This testing was not done on the generator, but was fed from the mains. The pump will now run on the 5kw generator, but the lights dim pretty bad.

I would like to apologize to everyone here for any confusion created by my comments. Darkblack, thanks for your comment that finally triggered me to take another reading.

 

[RFB]

I think, to steer back to the issue, is that the OP needs to test his pump start and operating current.

Once he has those numbers everything else is pretty easy to calculate. (I still wonder about those relatively low amp numbers for a 3hp pump.)

So, to catdiva6, if you can perform (or have your well company) a load test for your well and provide that data, the answers become very easy.