Okay gents. I want a generator for hurricane season. For farm use and homestead from irrigation pump to home HVAC. I can do everything with 35kw and probably 25kw. Here is my Q. I have three tractors. Tractor HP is 28, 36, and 100 all of them have at least 540 and 1000. Can I get a 25kw and if I need to run a few things use my smaller tractor and if I want to run my air conditioners just hook it up to the 100hp tractor? Trying to find real world info. Thanks
PTO Generator Questions
- Thread starter chamjoe
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Popgadget
Elite Member
Short answer is yes. You typically need 2hp per KW output, so your 28hp tractor would be good for about 14 kw before it’s starts to bog down. If you get a 540 rpm generator, you could use the 1000 rpm on the bigger tractor and run it at less than half speed to get 540 at the PTO shaft.
Sawyer Rob
Super Member
Thanks for the response. What HP and KW you running? Does it really strain your lower HP tractors?
I guess this is where I get confused. Set aside the 540vs1000 thing. The load is somewhat linear and based on pto RPM, right? So how do I produce 14kw on a 28hp and more on larger tractor? I guess what I’m worried about is that I can’t push a 25kw generator with the 28hp tractor at any RPM.
ruffdog
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You can "push" a 25k gen with 28hp but you can't power 25k with 28hp. It takes about 2hp to power each kw.
sea2summit
Super Member
The load is linear so you need ~2 HP for/KW, however to get the right frequency you need the tractor operating at ~540 PTO RPM which has most engines producing their max HP even if the load is 1KW on a 14KW generator so when the load surges to 14KW in theory the tractor wont notice (but it can/does). Ideally you'd want a fairly consistent load or a cruise control on the tractor to keep cleaner power going. The generator wont produce more power than it's rated for (for simplicity sake we'll assume that's true), so hooking up a 60PTO HP tractor to a 14KW gen set should only produce 14KW but hooking a 12 PTO HP tractor to the same gen set will only support a ~6KW load before it stalls out the engine.
Hope that makes sense.
Doughknob
Veteran Member
OP, a generator turns easy when you have nothing that wants electricity from it. Once appliances start start drawing juice from it, that is when it gets harder and harder for the tractor to turn it.
RickB
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I ended up with my dad's 25kw Winpower generator from the farm. I ran our whole house with it on a 42 PTO hp David Brown 885 with a 2 speed PTO which turned the output shaft at 540 at about 1200 erpm. I never measured the load but it ran everything on a half gallon of diesel per hour except the tractor would not make enough hp at that engine speed to run the central AC. It did that easily with the PTO set at the regular 540 at rated speed.
CADplans
Elite Member
As far as powering the heat pump,,
there are several factors that are involved in determining the power needed ,,
1) cooling capacity of the pump,, a 2 ton unit takes far less starting current than a 3 ton.
2) compressor type. My daughter has a heat pump with some sort of screw compressor,, I never see the lights dim when that thing starts,, it is like a variable speed start, showing no extra load due to starting. Heck, I have a little window unit in a small, remote office,, 6,000 BTUs, IIRC,, that thing will dim the lights when its piston pump tries to instantly come to full speed,,
3) the setting of the thermostat,, some new thermostats can be set for a longer delay prior to restart,, insuring the system pressure is low prior to restart.
4) I am sure there is other factors.
there are several factors that are involved in determining the power needed ,,
1) cooling capacity of the pump,, a 2 ton unit takes far less starting current than a 3 ton.
2) compressor type. My daughter has a heat pump with some sort of screw compressor,, I never see the lights dim when that thing starts,, it is like a variable speed start, showing no extra load due to starting. Heck, I have a little window unit in a small, remote office,, 6,000 BTUs, IIRC,, that thing will dim the lights when its piston pump tries to instantly come to full speed,,
3) the setting of the thermostat,, some new thermostats can be set for a longer delay prior to restart,, insuring the system pressure is low prior to restart.
4) I am sure there is other factors.
Thanks for the reply guys. I guess I wrongly assumed that the power produced was set and didn’t vary based upon demand draw. They’re *smarter* than I thought. I guess simply, it’s like any other implement like a bush hog where I can spin an 8’ mower with 28hp but sure can’t mow very fast without it bogging down.
okay. Now to go shopping! Any recommendations? Guess I’ll shoot for 25kw. I do have a 3-ph elec pump but everything else is single so will start the hunt for that.
to the commenter on running central HVAC, they make these soft start modules (I assume it works like a capacitor booster) to hook up. I don’t have one yet but know folks that do and swear by them.
okay. Now to go shopping! Any recommendations? Guess I’ll shoot for 25kw. I do have a 3-ph elec pump but everything else is single so will start the hunt for that.
to the commenter on running central HVAC, they make these soft start modules (I assume it works like a capacitor booster) to hook up. I don’t have one yet but know folks that do and swear by them.
ponytug
Super Member
Three thoughts: If you want to power your three phase pump, you probably need a three phase generator, but that may involve trade offs for everything else as most three phase is three phase "Wye" that produces 208/120, rather than "Delta" which can produce 240/120. Or get a variable frequency drive that accepts single phase and outputs three phase and keep it plugged in to keep the capacitors good. In both cases, check what your pump needs.
Second not every air conditioner works well with soft or hard start units, so check your particular model before going down that path.
Third, it is probably worth doing an energy budget for what you need to run and what you want to run. It may be quite different from what you think. e.g. our house idles along at about 200W, so the microwave (1500W) is a big draw, and the furnace is only 500W. The big, big, user is our AC, which we decided not to run without grid power. As a result, we can get by just fine on a 4000W generator, though our 6500W diesel generator handles the microwave and motor (booster pump, furnace) start up loads much better. This definitely a YMMV item.
All the best,
Peter
Second not every air conditioner works well with soft or hard start units, so check your particular model before going down that path.
Third, it is probably worth doing an energy budget for what you need to run and what you want to run. It may be quite different from what you think. e.g. our house idles along at about 200W, so the microwave (1500W) is a big draw, and the furnace is only 500W. The big, big, user is our AC, which we decided not to run without grid power. As a result, we can get by just fine on a 4000W generator, though our 6500W diesel generator handles the microwave and motor (booster pump, furnace) start up loads much better. This definitely a YMMV item.
All the best,
Peter
Thanks. I’ve got lots to run. I’m just going to ignore the 3ph irrigation pump as that’s the only thing running it. Last question. Should I get a 540 or 1000 RPM gen? They have the same tractor hp requirements so while my gut says to go with 1000rpm I’m not sure why. Btw, I’m leaning on the 27.5kw winco.
oh and my estimated max run load is ~15KW but the cost increase to go more to 25kw isn’t much so I figured why not.
ponytug
Super Member
Personally, I would get a 540 on the thought that you could throttle down a 1000rpm PTO to 540 for a quieter, and slightly more fuel efficient generation, especially if you aren't using the full 15/25kW of demand most of the time. I would get an inexpensive frequency meter that you can read from the seat of your tractor to set the rpms/ frequency accurately. Wincos have a good reputation, but I haven't personally used one in decades.
I would also take a quick look at Craigslist / eBay/ auctions for used diesel standby generators. They can go for really cheap, and they are usually very lightly used, but it depends on your local market. Here Craigslist is pricey, but auctions are cheap.
Finally, before you pull the trigger, have a look at other generators one last time. (Propane, gasoline...) Sometimes I can get so far down a path that I forget to double check the alternatives.
All the best,
Peter
I would also take a quick look at Craigslist / eBay/ auctions for used diesel standby generators. They can go for really cheap, and they are usually very lightly used, but it depends on your local market. Here Craigslist is pricey, but auctions are cheap.
Finally, before you pull the trigger, have a look at other generators one last time. (Propane, gasoline...) Sometimes I can get so far down a path that I forget to double check the alternatives.
All the best,
Peter
Thanks for the tips. You might be right on the 540. I’m definitely worried about noise so I will be keeping on the Htz. I’ve even looked at directly buying mil surplus gens but I’ve got 3 meters on-site and I’m about to have a fourth so the idea that I can plug and play at different locations without adding a new motor to service myself seems like a winner especially for ~$3k.
Sawyer Rob
Super Member
Like was already said, the generator doesn't turn hard without a load on it. As the load increases, you need more HP to keep up with the load.
For light loads, I run my Winco 15kw pto generator with my 12.5 pto hp tractor. If I want to run a bigger load, I just run the generator with a bigger tractor.
At 12.5 pto hp, I can easily pull 6,000 watts out of my generator, and that's more electricity than I "need" to run my whole house during an outage.
SR
Larry Caldwell
Super Member
If you have HP to spare, a 540 rpm generator on a 1000 rpm shaft lets you reduce engine speed and save fuel. If you are pushing the engine, there's no difference. My little Kubota has to run at 2200 rpm to generate 15 kw, but a 60 hp tractor might only have to run 1100 rpm on a 1000 rpm PTO.
Plus, every tractor has a 540 rpm PTO. 1000 rpm not so much. If you buy a 1000 rpm generator, you limit the tractors that will run it at any load.
Plus, every tractor has a 540 rpm PTO. 1000 rpm not so much. If you buy a 1000 rpm generator, you limit the tractors that will run it at any load.
workinonit
Elite Member
I have a 25 kW Winco. I mounted it on a trailer with a distribution load center and a 100 amp welding recepticle setup with a matching one in my shop so all I have to do is plug and kill the mains on my 2 200 amp panels. I have an LED wired to the top of the meter base so I know when grid power is back on. I ran that generator supplying my whole house on my old JD 5310 (55 HP) using economy PTO at 1700 RPM. Never had it bog down at all. My new tractor is a 5090 so there's no issue running it now. Mine has a frequency/volt meter installed on it. I check it with a Fluke everytime I run it to make sure the meter is still in cal. My 5310 didn't vary the voltage at all when I loaded the gen up. Good governor I guess.
