Generator PTO Generator

[Anonymous Poster]

i have had a pto genset for a few years, i have a generac 25kw model it includes a volt and freq. meter that you can see from the operators seat. you can probabley buy a good stand alone unit for less, from northern, etc. i have a NH 15 20 with about 19 pto hp, this will give about 9 kw of power from the unit 2hp= 1kw. you will need to run your tractor at the 540 pto mark on the pto, then adjust it using the freq. meter which is more sensitive than the volt meter. i have usually set min at about 60.7 hz without load this will keep the range within about 60 hz with motor startups etc since there is no governor on the unit. runs the whole house just fine, i think you need to think of these things as industrial quality units, that run almost forever, need almost no maintenence, it weighs over 500 lbs without the trailor, and with a 100 hp tractor would run three or four houses easily. it does tie up the tractor, but i dont have to service another infrequently used motor, it will last easily the rest of my life and most likely that of my children. the dairy and poultry farmers swear by them, not at them, thats enough for me.

as for other portable units you can get a gasoline unit for of equiv. output for less than i paid for this genset, the problem is will it be ready to run when you want it. the stand alone units should be run every few months to keep them lubed, and the fuel needs to be kept fresh, oil changed, etc. the pto unit is in the shed with a tarp over it, i run it for about two hours per year hooked to the house for about an hour then back in the shed it goes, in about 5 years i will need to change the gear box oil, that's about it.

al

 

[alexcocco]

i am registered now thats my post above.

 

[TomG]

Some PTO generators have a frequency meter, which is a very good idea. Engine RPM determines the AC frequency. If the frequency is very far off, electric motors will speed up and loose power or slow down and burn out. Without a frequency meter, seconds from an AC electric clock with a second hand can be compared to a battery clock.

When choosing a PTO generator, the tractor should be over-powered for the generator. With an under powered tractor, changing AC load exceed the tractor governor's capacity to maintain engine RPM. The AC frequency reduces, and electric motors burn out.

Myself, I wouldn't want a PTO generator for emergency power backup. I'd just end up having to swap implements at night during storms before getting the 'emergency power' on. I usually hear of PTO generators used in dairy operations that have requirements for a lot of emergency power. My little Honda 6500 will run my house OK for an extended time during an emergency, and I'd pay more than the Honda cost for the PTO generators I've seen.

 

[alexcocco]

my experience with the pto generator has been this , as long as you are mindfull of your power use it is just like any other motor driven generator, it is highly unlikely that you would need more than 9kw to run your house, even my 19 pto hp tractor will deliver this from the generator, frequency meters that are built in are nice, but you can get a multimeter with a frequency scale for about $45 from amprobe or fluke, i have one, it works well, when i am on generator i check the freq. in the house at various outlets under various load conditions, unless you have a 5hp motor to start, you wont need the full 25kw output of generator, with the diesel engine and the mass of the armiture of this large generator i have found that it is less likely to lose frequency than the smaller gasoline powered units that i have owned on motor startup. i have tried to create these low output conditions by placing very heavy loads on the generator, with my settings as noted above i have not been able to create a freq drop of greater than 2 percent transient on motor startup, this includes washer, furnaces, well pump, dryer, refig , freezer and lights as well as the misc. electronic gear in the house, i more or less turned everything on in the house that is on the generator sub panel almost simultaneously without problem of frequency drop. try that with a gasoline powered unit you will most likely stall the motor or at least see severe freqency droop and sine wave distortion.
understand that this unit is rated for a 50 pto hp tractor for full output. so oversizing of the tractor will only use more fuel, not necessarily give you a more stable power supply, this would apply only if you were using the generator at 100 percent of rated power, for most of us the 25 kw potential of the generator will never be needed in a residential use.

more appropriate is to be sure that the load attached is equivalent to about 85 percent of the generators output, leaving 15 percent as a reserve for start up of motors etc. this will yield the most efficiency from your generator.

these same observations were relayed to me by a now deceased friend who had spent many years working in underdeveloped countries and had much more experience than i do as far as power generation under field conditions. that was one of the prime reasons that i went with the pto generator.

good luck in your choice
al

 

[dmccarty]

Al,

Are you using the generator with well and septic pumps?

When we get the house built I'll need a generator that has the muscle to power a pump at about 350 feet, at least one septic system pump, as well as the fridge/freezer/hotwater heater/lights in the house. I don't plan on running all of these things at the same time especially the pumps. I figure when the power goes, I'll run the generator an hour or so first thing in the morning, around midday, sometime in the evening and again before going to bed. I figure with that schedule we would "flush" the septic system, give us water, keep the fridge/freezer cool, and maybe give us some hotwater. Those are my primary electric needs. Lights to read/see would be nice but I'm not going to run the generator just to read the mail.

Thanks...
Dan McCarty

 

[alexcocco]

DM,
i have not had to run the water heater which would be aboout 4000 watts, i have a 3/4 hp well pump at about 75 ft, we dont need a septic pump, as far as everything else that you talked about i have run the house including washer and dryer with my tractor, how long will you be off the grid? if this is a permanent situation you may want to look into a battery/inverter setup i built a cheap one for under 1000 dollars with a 3000 watt inverter and some deep cycle batteries that you can charge when the generator is running, this would give you lights, and a few low drain items that you could use when the generator was not running.

i saw a combination frequency and volt meter that plugged into a regular outlet in the new harbor freight catalog as well as a volt meter only unit might be a good thing to have. would let you check your freq. and voltage anywhere in the house.
what you need to figure out is how much power you need, one of the best web sites for an education on off grid power is the juice page, this will tell you about motors, generator sizing, etc.

if you are planning to run a pto generator i have seen these in 12, 25, 35, 50kw sizes. the 25kw seems to be the most popular and the quality farm and fleet and central tractor stores usually have one or two in stock around here. there does not seem to be that much price difference between the 12 and 25 kw units. since i doubt you will need all 25 kw to run your house, you wont need 50 pto hp to run the gen. at max output. you will have to figure out how much electricity your tractor is capable of producing- 2 pto hp =1 kw electricity. then you need to figure out what devices you can turn on simultaneously to add up to your output. you want about 85 percent of your output to be in use with 15 percent reserve.

you will want to install a transfer switch before your main breaker panel, or you can get a small sub panel with a transfer switch built into it. i put in one of these which will handle 100 amps and you add your own breakers for the various circuits a few parts of the house arent on the generator but most of it is. these are the safest ways to connect a generator and i would urge you to use a transfer switch of some type for protection.

from your list of items to run:
well pump= 2 hpX740 W/HP=1480W x2 (startup amps)=2960w
water heater= 4000w
lights= 500 w
furnace=2200w
refrig= 1000
freezer=1000
septic pump 3/4 hp=500w
total 12,160 Watts
you will need to correct the values for the name plate ratings on your appliances,pumps, furnace etc.

if you need any other info let me know.

alex

 

[TomG]

It's a good idea to check local codes before buying equipment to hook a generator into a residential service. Around here, codes require a 3-point disconnect from the utility lines and a unit where the utility and generator lines physically cannot both be on simultaneously. I bought my equipment when codes were changing and new equipment was being evaluated for approval. I guess there was a possibility I could have ended up with equipment that would have a hard time getting past inspections.

I bought a 60A sub-panel that is fed from the service panel. The sub-panel was much less expensive than a transfer switch ahead of the service panel because the transfer switch has to be rated for the full residential service. However, using a sub-panel does require some circuits to be re-wired. Line splices in junction boxes are needed to extend some lines to the sub-panel. The sub-panel route was cheaper for me since I did the entire installation. If I needed an electrician, the transfer switch might have been cheaper.

I made a decision to go small with the generator. I figured the idea was emergency backup, and I didn't need to run everything in the house as usual, even during an extended outage. The generator is capable of running everything individually, but I have to shut some stuff down to run the water heater, or during heavy stove use.

The decision to go small cost less and let's me get away with a standalone unit. Maybe I'll wish for a larger generator if we ever get an outage long enough to really need more hot water. However, right now, I'm just happy that I don't have to mount a generator on the 3ph to restore power.

 

[dmccarty]

Alex,

Thanks for the info. I had roughly figured that I would need a 12-25KW generator. I would do a final tally when I acutally lived on the property. My current house has a power access from a major road so when the power does stop because of storms we are one of the first to get back into service. After Hurricane Fran hit I lost power for maybe 12 hours and that was overnight. The subdivision right next to mine which is much more expensive and built a few decades after my 'hood was out of power for over a week.

In the last few years we have had two major snow/ice storms and three hurricanes, Hugo, Fran and Floyd, plus numerous little ones. The area our property is in was without power for about a week after each storm. That is the outage duration I'm planning for every year or so. What is ironic is that I'm from Florida and I did not have that many serious hurricanes when living in down there. Hurricane Andrew set the tone I guess since it hit South Florida, where I used to live, the week I was moving. I litterally got the rental truck loaded and on the road as the first rain bands started to show up from Mr. Andrew. I was acutally climbing into the driver seat with the rain started. WAY to close for my comfort!

If I'm without power for a week I'll want to have a hot shower! I don't plan on running everything at one time but if the equipment, generator and tractor, can handle the load I guess I will.

We will have a transfer switch. From what I have been told the county is pretty strick on generator hook ups which is fine by me. I HATE messing with power. I have a Fine Homebuilding article somewhere on transfer switches and I'll reread it and do more research when we build the house. I want this part done right with no problems. I don't want to be zapped dead and I don't want to kill a lineman either.

One question though, I thought the number of amps produced by the generator would be more important that the watts? But I guess if the generator is 12KW and it only supports 120volt then that is 100 AMPS. I guess I still have to make sure the any 240v line are supported with the right number of watts/amps.

The last time I priced standalone and PTO generators the later were the biggest bang for the buck. I had no way to tell which was the better quality unit bt the PTO units were much cheaper and provided more watts.

Thanks....
Dan McCarty

 

[alexcocco]

>dan ,
you should always buy a generator on the continuous watt rating, those momentary ratings sound large, but there appears to be no industry standard as to how to how long is momentary some use a time as short as 10 seconds.they are meaningless.i think the momentary rating on my pto generator is 50kw.

i neglected to tell you that when i bought my generator it came on a trailer, this or a concrete slab seem to be the reccomended ways to mount these large pto units, apparently they can flip over if a large load is applied suddenly so manufacturers feel some type of broad based support for the
generator is required.

also some of the farmers around here attach a 220
volt welder to their trailers and use this as a portable generator /welder rig to use in the field.

your ideas of a transfer switch echo mine, i bought a 100 amp gen-tran sub-panel from northern tool and had the essential circuits moved over by an electrician.

i made my own cord set from a 25 ft. #10-3 extension cord and the proper plugs to go from the generator to the transfer switch, pulling full load after 1 hour the cord wasent even warm. best place i found to buy the cord was at walmart in the R-V section the orange cord was 27 bucks, the wire alone was 1.25/ft at lowes. i made up a separate ground cord from
some green (ground) #10 wire and two large battery clamps for the ground. i think its a good idea to always have a separate ground on your generator. you may want to discuss this with your local electrician. you should always seek help with things that are as potentially lethal as electricity, i am not reccomending anything to you just telling you how i did it.
if you have any other questions about the generator i will help if i can.

good luck on your new place,

alex

 

[dmccarty]

Alex,

Thanks for the new info. I forgot to ask buy what brand of generator did you get? The trailer is the one thing I don't like about the PTO generators I have seen. I really wish they could run on a 3PH hitch mount/platform of some sort. That way I could use the tractor with the generator mounted.

Thanks again...
Dan