20 KW Generator Questions

Well it seems I have a 20 KW PTO generator being given to me.

A few months ago I heard about a guy at church who is living in an RV and wanted to get his house built. He has a saw mill, but only 14 acres. Me, I got a few more, and I felt bad because in a lot of ways I have been blessed with so much, so I tell him and his wife we will give him the wood he needs to build his house, probably 10,000-12,000 board feet or so of hemlock for those on here who are interested in such details.

Well he finds out we have just a small generator and says, "I got a 20 KW PTO generator someone have me, but I don't have a tractor, so why don't you have it. It's been in storage for 10 years." I am like, "Well keep it until you get a tractor", but he insists.

But the thing is, I think he might have a tractor already as he has a 1963 John Deere 1010 bulldozer. That bulldozer is unique in that it already has a pto installed, and while it is a gasoline engine, it has 36 hp, or what Nebraska tested at 27 KW at the PTO. Yet people have said I need 3 hp for every KW? I always thought 1 HP equaled 750 watts. If I did the math right, it would take 26 hp to power the generator. At the same time, this would only come into play IF the electrical load on the generator was at 20 KW...an incredibly high load to say the least. If it was say half that, 10 KW it would not require 26 HP, or am I missing something?

I say all this, because as much as I would like to have the generator, if the guy can use it with what he has for a tractor, I am not going to take it from him.






If I remember right they have PTO's so I am going to make double sure he does not want to keep it. If I did the math right he would need 26 hp and a JD 1010 gas engine should have at least that, and even then, that is at full 20 kw production...righ

 

I compared online specs of a 25kW and it recommends 50HP. That being said, your conversion is true minus the startup overhead as well as "max PTO" as it may derate quite a bit over extended periods of time. So yeah, he can use it, not many folks really need 20kW if its just for use during power outages.

 

On average you need 2hp per kw, however it will only produce what the tractor will put out, so you can run those on a smaller tractor and only get say 10-15kw if that's all the tractor can support.

Those PTO gens aren't the most economical power sources but are pretty convenient. My parents have a 10 or 15kw PTO gen, and it gets run off the farmall c most of the time, usually in the fall that tractor is backed into the barn and sits hooked to the gen since it's not used alot and has a better track record for cold starts.

 

Keep something in mind. When are you ever going to pull a full 20kw out of the genny ? If youre just going to use it as a backup for your house, its pretty rare to pull that much power unless every appliance you own is electric and you just HAVE to dry a load of clothes, run the shower, and have all 4 burners plus the oven going, all at the same time. If its got some other high draw purpose, well then, just ignore me.

 

Our 175KW Baldor genny at work has a 200 HP JD for power...so just over 1 HP per...works just fine

 

My biggest draw is my electric hot water heater, though everything else I have propane (like our kitchen stove/clothes dryer/etc). I do need to add a Boiler Mate someday to stop that nonsense), but until I do, showers were out of the question for my small 4000 watt generator.

During the last power outage, the coffee pot and toaster would sometimes throw things out of whack, but just guessing I would say, worst case scenario we might draw 9 KW.

This is our kitchen range, and while not the Survivor Farm Girl of the thread "We are Doing it All Wrong", but since it seemed that lady generated interest, I'll add one of Katie standing in front of her 1917 Crawford Propane stove in 1930 era attire.

 

I might have some experience in the run a house on a generator like 3 weeks worth... 9kw will not run a house! But if you need too.. why loose a piece equipment... a 60k army surplus generator can be had for 350 dollars towed diesel... after weeks without power .. I can say go big or go home.. especially if your house is mostly electric as many are aware it' not volts that matters anyway its amps! try explainig to 12 you no curling iron straightening iron not to mention toaster microwave etc etc

 

It has 60 Amps...what does that mean?

 

That generator with either your tractor or dozer will run your whole house, When I was looking at automatic gens last summer, both the briggs and then generac dealer wanted to install and 10-11kw with a module to separate the water heater and the oven from kicking on at the same time, if I wanted to run the a/c then it was the 20kw system.

The generac site has a calculator there that you can play with. Its assuming an automatic gen though, but can give you an idea.

Edit: Some pto generators are better than others as far as power required, it also depends on the engine that is driving it.

 

what is your panel box 100 or 200 amps... for instance my well pump only draws 8 amps.. but a toaster oven can draw 12 or more? electric water heaters girls bathroom stuff are big amp appliances

 

I have a 6 cylinder White diesel engine sitting on an engine stand with a hand clutch, but I am pretty sure it would be over kill. I was going to install it in one of my sawmills but never did. :-(

PS: I think I use more emoji's then a 12 year old in a texting completion!

 

Service entrance is 100 amps. My house is wired via the new method of using circuit break boxes and not home-runs like the old days, though so it might change things a bit.

 

I did a calculator on line and it said I should be okay, 12,000 watts an 56 amps.

I am not sure if his little bulldozer would power that much, but it seems as if my bulldozer would (a John Deere 350D with 48 HP PTO power)

 

si if this one good for 60 amps figure it can run half your circuits and then figure what are most important then try to not run oven toaster and bathrooms at same time.. if I remember correctly you have teenage girls IF so that calculator is WRONG

 

True, the problem is I typically just snap the main breaker going to the line so it does not back feed, but man can a wife and 4 daughters do a number on a 4000 watt generator. It never stalled, but it stumbled a few times.

I told them over and over again, "you can't just flips anything you want on"...No use, the little generator would just sputttttttttttttttttttttttttttttttttttttteeeeeeeeeeeeeeeeeeeeeeeerrrrrrrr.

 

OK I have a 4000 watt my house is mostly not electric.. propane stove, oil hot water, 4kw ran fridge freezer kitchen lights and 4 power strip BUT not water.. so to have water fired up back up 6 k for coffee pot, water etc 5 to 7 am and pm when girls needed their stuff... even that with blow dryers had to limit what was on at same time

 

Well, we have to be really careful here I think with 'it takes XXX amps or watts to run a house'. With a little care, and avoiding using the electric clothes dryer, we did fine with a nominal 5KW generator. BUT, we only used one high -amperage heating device at a time while allowing the rest of the house to run normally. What I mean is that refrigerator, boiler, lights (as needed), TV, phones and all the other small electrical needs of the house were taken care of. In addition, we could use one high- current device (microwave, coffee maker, toaster, my wife's 'hair device' (whatever it is), hair dryer, etc.) at a time. That means once the coffee is made, the coffee maker has to be manually shut off before the toaster, microwave or anything else could be used. So all our real needs were taken care of, and we could live comfortably but not without using some care while running on the generator.

But- if more than two adults are in a house, and several people (let's face it: females) are using bathroom devices and kitchen devices at one time, then it will take more power to maintain a 'normal' life.

So that is the question I think: how do you want to or have to live with no grid power available? And how long is the electricity likely to be off in your area and your situation? We went a couple of days on the generator and simply did not dry clothes for that time; had it gone on a month like CBVT's situation did, we would either have to drape wet clothes all over the place or go to a laundromat. And there is the 'other shoe' that generator cost goes up fast as capacity goes up, and 'automatic' stand-by generators are far more expensive than portable or job site generators. So I do not think there is a 'right' answer as to what size generator is needed, only what one is willing to pay for and live with when using it.

BTW: my brother used a 3KW generator for many years and a few years ago got sick of running 115 volt extension cords and plugging and un- plugging in things to use them, such as the refrigerator. He bought a 5,500 watt generator, wired it as two- leg, 230 volt power into his electrical panel and can now basically start the generator and have a pretty normal life. Much, much more convenient than having one 115 volt source to manually bring to devices as you need to run them.

Brian

 

Yep, you are right- there are 746 watts in one Hp (or vice- versa) but that is a no- loss conversion. Using a generator and internal combustion source to power it, there are a lot of losses; all the heat generated by both the engine as well as the actual generator are losses you have to provide power for. So what is really happening is that whatever your power supply in Hp, you cannot get all of that as electrical power. You will suffer some losses along the way and they are not small. I do not know what the 'rule of thumb' is for a small generator running from a piston engine but it will be a lot less than the direct conversion: probably 30% to 40% at a wild guess.

So your 36 Hp will produce perhaps (36 X 746 X .4 efficiency) is just over 10,000 watts of electrical power. Again, the efficiency of the whole thing is a guess on my part but I am sure you can easily look it up on the 'Net.

Brian

 

BDF, I agree it depends on length or time a few days or a few weeks makes a HUGE difference..BUT lodged tree has 5 women.. also realize now that homework has to be done on internet.. yes you can shut off appliances BUT hot water (he has electric) and wells pumps (I assume on well) with bathroom lights will not run on a 5500kw generator and my wife says "showerING by candle light is NOT romantic after 3 days " also the shaving of ladies legs requires lights I was told this also... But I am still married

 

Don't have a generator yet and not an electrician, but it seems that one thing is true. NEC requires that automatic generators be properly sized to ensure they can support the highest electrical load a system has historically had. Found this video interesting. Maybe a licensed electrician can comment.