PTO powered AC Generator and hours per gallon

[Drew 0]

I'm looking to fashion a 10K Watt generator head to my horse and run it off the PTO for home AC power backup. Couple questions...

 

1. Has anyone done this, running an AC generator head off the horse's PTO?

 

2. Does anyone have data on how many hours per gallon a Kohler K241S under no load at full throttle will run?

[bmsgaffer 2,043]

Spinning a 10KW generator head even unloaded is not "no load". I would highly recommend looking at a 3KW head for a 10HP kohler.

 

A minimum of 18hp is required for a 10kw generator fully loaded. You have to spin the generator at full speed (3600 rpm) so you cant gear it down.

 

You could just tell yourself to never run more than 3KW on it, but the increased overhead of a 10KW generator will cause it to be much less efficient. And if you plug something in that has "startup draw" you could end up stalling the engine or running it so hard into the governor that your speed would drop. Once the speed drops you will get less than 60Hz and possibly fry your equipment.

 

I would guess (based on mowing a lawn, which is less load than a 10kw generator probably even unloaded) you wouldn't see more than 2 hours on a tank of gas (~3 gallons). That wont improve too much if you get a 3KW generator but at least you wont have to worry about overloading the Kohler.

[Drew 0]

Hey Bms,

 

Thanks for the post. When I said "no load" i meant without the head, or mower, or anything connected as I know someone couldn't comment on how much gas it would take not knowing the exact load. I was looking for numbers if the Kohler set by itself running full throttle and would extrapolate from there.

 

Good thoughts on the wattage.

[bmsgaffer 2,043]

Gottchya.    I am not sure I have ever seen gallons per hour, but maybe someone will chime in here with more experience than I. They probably didn't list them because it will depend on elevation, temperature, humidity, gas etc...

 

BTW, Welcome to Redsquare!

 

I look forward to pictures of how you do it, I have been interested in doing that for a while but $$$ for a decent belt driven generator head have prevented me.

 

Oh and several people have done it, WH even offered it as an official attachment for a while (check out the For Sale section, 3 just sold there recently). Or search for 'generator'. I know of at least one guy who made his own that fit into the attachmatic.

Edited April 4, 2014 by bmsgaffer

[Sparky-(Admin) 19,677]

  My neighbor has a 10k on a 416 and it definitely works the governor when he's powering the house. I think a 10hp will struggle with a 10k gen head, might not even be able to keep up and it'll start losing RPM's under load which will lower the voltage which raises the amperage which just compounds the problem. If you buy a 5000watt portable generator unit they generally come with a 10hp motor. The 4000 watt units are 8hp for the most part.

  I think Brandon is right about having 18hp to get good performance from a 10k gen head.

  I have no idea how long an unloaded 10 will run on a tank.

Mike...........

[can whlvr 991]

my 5500 watt genny has an 11 hp the rule of thumb,500 watts per 1 hp

[Save Old Iron 1,563]

Run time at no load can be calculated

Calculate your cylinder volume

Then the volume of air your engine pumps per hour

calculate gas and air weight per gallon

Figure a 14:1 air /gas mixture . by weight

Figure how long your engine will take to consume1 gallon of gas by weight at a 14:1 mixture

Multiply this time by your fuel tank capacity

There is your answer

All the math can be done by googling physical properties.of gas / air / cylinder volume

Or search this site -I made this calculation before

Edited April 5, 2014 by Save Old Iron

[WH nut 553]

That's too much math SOI lol. Grab a six pack, fill her up and wait. My 310 will go about 4 hours on a tank mowing.

[shorts 182]

    welcome to RS,

 

I spent some time working with generators and standby power, the actual conversion ratio is 1 kw = 1.54 hp so that puts your 10 hp engine at 6.49 kw rated power.

If you are using the generator to start and run electric motors like the furnace blower, sump or well pump, freezer or refrigerator compressors you need to look at the hp rating of the motors and then figure 3 times that power to stare the motor and whatever the rating is to run it after it starts.

 

With all of the math out of the way if I was going to make up a generator attachment I think that I would probably use a 10kw head knowing that it would not make any more than 6.5 kw unless it was put on a tractor with a larger engine.

Another thing to be aware of while shopping for a generator head is the power rating intermittent, like for starting a motor vs continuous for running a motor. as you try to manage your power usage keep in mind that typically compressor and pump motors start under full load while fan and blower motors start under light load that increases as the speed picks up, start your highest load motor first and then add the other loads 1 at a time and stop when the speed drops, 3600 rpm for the engine or 60 hz @ 120v for the power