PTO generator

[crazyal]

A rule of thumb I was told by the well drillers was 3x. What ever the current draw under full load for the motor should be multiplied by 3 to determine the inrush current. If you look at the Generac manual for their generators confirm this. Here's a Generic manual for a 5000w/ 6500w portable generator. In the table on page 7 for submersible pumps they say 1500w for 1/2hp, 2000w for 1hp, and 2800 for 1 1/2hp with an asterisk. At the bottom of the table they have this "* Allow 3 times the listed watts for starting these devices".

I would use their numbers as a rough guide but I can tell you that my 4200w/ 5000w surge generator is at it's limits starting my 1 1/2hp well pump. You can do what ever math you want but in the real world I can hear the engine work hard. If it's at night and I have a light on it'll dim the light quite a bit when dealing with the inrush and then just slightly as it steadies out. Once the pressure switch kicks off you can see the light get a little brighter. Since I had the generator before the well and it's in great shape I'll use it for now. But if I had to buy (or give advice) a generator the smallest I would get would be 5kw for a 1 1/2hp pump.

http://www.electricgeneratorsdirect.com/manuals/5623manual.pdf

 

[stonypass]

As long as we are talking generators,I'm considering a portable gas generator for use during outages.My main concern is how much current is needed to start my well pump.I have a 450' well with a 1 1/2HP Goulds pump.It runs fine with a 240V 15 amp circuit breaker.I really don't need to keep everything in the house running all the time,just a little furnace here,or the fridge a little,etc.I just don't want to hurt the well pump.Would be happy to turn everything off just to pump some water.I've been looking at 5500 run/6900 peak or 6500 run/8000 peak units.Would one of these be sufficient?Or simply how many peak watts needed to start my pump?
Yes,I'm asking this on a tractor forum.We rock here!Thank you in advance for your replies.

My pump is a 1 1/2hp 10gpm pump down 500' with about another 30 feet up to the house. The static level of the well is between 50' and 100'. I have a 4200 watt generator and when the pump first turns on it's about all the generator can do. I would say a minimum of 5000 watts would be needed IMO. I use mine and never had a problem but I do have a large storage tank so I don't need to run the pump very often.

Just set up my home with a 12/15KW PTO generator and finding out the actual draw of items in our house was a priority for me.
We also have a 1 1/2hp deep well that's 650' deep with the water at 160', the clamp meter I bought at HF shows it draws 9.5amps when running.
Our well service who installed it said you need 5kw for our set up and I think that's about right considering the start up draw.

After testing I find that with 12KW I can run the well and any other single high usage item (Clothes Dryer, Range/Stove, or 4ton AC Unit) along with lights, fridge, freezer and Electronics with no issues.

 

[Rob-D]

Just set up my home with a 12/15KW PTO generator and finding out the actual draw of items in our house was a priority for me.
We also have a 1 1/2hp deep well that's 650' deep with the water at 160', the clamp meter I bought at HF shows it draws 9.5amps when running.
Our well service who installed it said you need 5kw for our set up and I think that's about right considering the start up draw.

After testing I find that with 12KW I can run the well and any other single high usage item (Clothes Dryer, Range/Stove, or 4ton AC Unit) along with lights, fridge, freezer and Electronics with no issues.

If I had my way I'd run springs over wells.I have several springs here and one that runs even when things dry up, the good thing is that it's above the house so I can gravity feed it, although I also have to dig down about 4 feet to keep it from freezing. My neighbor has one that he lets run constantly so it never freezes. Everything you can do to reduce your usage extends how long you can be without grid power.

 

[sdkubota]

Generally most shallow water is contaminated with something or another...maybe not enough to kill or significately harm you though. Water from deeper wells is generally much better quality. All water should be tested as 80% of all wells have contaminates.

 

[Rob-D]

Generally most shallow water is contaminated with something or another...maybe not enough to kill or significately harm you though. Water from deeper wells is generally much better quality. All water should be tested as 80% of all wells have contaminates.

I don't trust either. We have two filters and UV before the tap.

 

[sdkubota]

I don't trust either. We have two filters and UV before the tap.

Many contaminates can not be removed by filtering. It is well worth the $50 to have your water tested by a laboratory to let you know if everything is good or you need to get a different water source. There are areas with elevated selenium that will kill you dead in short time. You probably don't have that problem since you are still here. children can be much more sensitive to certain contaminants and a parent needs to know what they are drinking.

 

[PineRidge]

Called customer service and after some checking she said the supplier shipped out some with an inappropriate pto shaft. They are going to send me a new one. When I talk with a live person at Farm King they couldn't be nicer...their IT must be a real joy given my email responses.

Glad they are making it right for you.

 

[Rob-D]

Many contaminates can not be removed by filtering. It is well worth the $50 to have your water tested by a laboratory to let you know if everything is good or you need to get a different water source. There are areas with elevated selenium that will kill you dead in short time. You probably don't have that problem since you are still here. children can be much more sensitive to certain contaminants and a parent needs to know what they are drinking.

I had it tested 20 years ago when I built the house but that's a good idea and I'll have it tested again.

 

[Slab]

That's great IF the PTO HP can handle the lack of gear reduction. PTO generators run ~2600 engine speed to 540 gen speed. A PTO HP rating of 25 at 540 rpm from an engine spinning at 2600 rpms has greater torque than the same engine running at 1000 rpms with a PTO of 540. Think of your car trying to pull you up a hill from a dead stop in top gear.

So, are you saying I won't have to run my tractor at 3200 rpm to get the 540 pto speed make the gen run properly.

 

[aczlan]

So, are you saying I won't have to run my tractor at 3200 rpm to get the 540 pto speed make the gen run properly.

Correct, but you will only have 1/2 the PTO HP available to work with.

Aaron Z

 

[PineRidge]

Correct, but you will only have 1/2 the PTO HP available to work with.

Aaron Z

On a 15KW PTO-generator the PTO speed is 540 but the gen set is runnng at over 3600 RPMs due to the gearing. At 540 RPM PTO speed my generator is kicking out 240 volts, at 60 cycles and is capable of producing 62.5 Amps

 

[Yooperman]

So, are you saying I won't have to run my tractor at 3200 rpm to get the 540 pto speed make the gen run properly.

I can only speak for my BX25 and pto generator. I MUST run my BX25 at 3142 rpm engine speed to get the pto at 540 rpm that my pto generator MUST have.

I don't know about others. :confused2:

 

[PineRidge]

I misunderstood you, I was talking PTO RPMs vs generator RPMs. I believe my New Holland is running somewhere close to 2600 engine RPM to achieve 540 PTO RPMs

 

[dex3361]

That's locked rotor amps! What happens when you lock a rotor on a motor? You blow the breaker! It's not the same as starting amps.

Motor Calculations | NEC content from Electrical Construction and Maintenance (EC and M) Magazine

" Motor locked-rotor current. If the rotating part of the motor winding becomes jammed so it can稚 rotate, no counter-electromotive force will be produced in the motor winding. This results in a decrease in conductor impedance to the point that it痴 effectively a short circuit. What痴 the result? The motor operates at locked-rotor current, often six times the full-load ampere rating, depending on the motor Code Letter rating [430.7(B)]. This will cause the motor winding to overheat and be destroyed if the current isn稚 quickly reduced or removed."

Electrical Motor Calculator

Plugging in 1 hp , 90% efficiency, 85 PF (power factor) and 230V to the calculator in this link.

You get:

1 phase = 4a.
FLA = 5A

What does FLA stand for? Full Load Amps! At full load the motor draws 5A, 230V * 5A = 1150W; 1 HP = 746W FLA for a 1 HP motor = 1150/746 or 1.54 times.

Now look at the chart for starting amps, what does the FLC state? 150% to 300% of running current and what's 300%? It's 3 times, exactly what I said. I work with this stuff everyday my systems are built on these calculations. Are you off the grid running several inverters on a daily basis?

Rob look at your pic of the starting current notice the first peak is 600% the FLA. Here is a quote from your link. "a. For full voltage (DOL) starting, starting kVA= 6*rated kVAod the motor . Use the nameplate LRA data or Code letter where available."

 

[aczlan]

On a 15KW PTO-generator the PTO speed is 540 but the gen set is runnng at over 3600 RPMs due to the gearing. At 540 RPM PTO speed my generator is kicking out 240 volts, at 60 cycles and is capable of producing 62.5 Amps

Correct (for a 2 pole generator head, a 4 pole head would only need to be spun at 1800RPMs), but I was talking about switching the tractor to use the 1000RPM PTO setting (if equipped) with a lower engine speed to power the generator at 540PTO RPMs. When you do that, you lose 50% of your PTO HP (+/- the difference in the torque curve between ~2600 engine RPMs and ~1300 engine RPMs.

Aaron Z

 

[Charlesaf3]

Couple pieces of exhaust pipe connected to the exhaust pipe of your tractor with a silicone hose should do the trick. Make sure to setup a remote kill switch outside the garage and a couple of CO2 meters in the garage...

Aaron Z

Yeah, I was thinking something like that. Only holding my breath - garage is small...

 

[Charlesaf3]

The trouble with that is the Xantrex for the truck is 12v. So let's say your house uses 2Kwh, that means 2k/12 = 166 amps draw from your battery and alternator. That's ok for small stuff like running a sander or lights on a job but your house most likely uses more than the 2Kwh I conservatively used in this example. For instance my off grid system is 48 to 72 volts nominal. (24v panels) Two 24v panels will run anywhere from 60 to 80 volts into the inverter, my other panels are a srting of 3 for 72 volts nominal or about 105 volts when the sun is running them. The higher the voltage the less copper wire for your runs. That's what you want, now back to the 48 volt battery bank that these panels charge. With the 2Kwh we used above: 2000/48 = 41 amps worth of copper. So to run an inverter from a battery bank you want at least 36 to 48 volts. So how do you charge that from your vehicle? Well, you'll need a special alternator and charging system. That's why your inverter system isn't the best. After you start putting appliances, etc. on the load end you won't be able to maintain them.

I agree, hence the 17kw hard piped natural gas generac - I think you missed that one above. Xantrex is just always available power - I can get 20 amps short use, say 8 amps constant at idle from it - alternator is rated 130, but I'm sure less at idle. Fine for job sites, might be able to run a fridge in an emergency

Oh, and I ran 0000 wire between the battery and the inverter, as specd by xantrex engineers. That was expensive...

If I need the full 20, I'll upgrade to the big alternator (350amp). I wonder if I can use the truck as a welder?

 

[Charlesaf3]

View attachment 287010

Someone asked about running the tractor inside with the door closed. This is a photo of my setup, since modified slightly for my current tractor. The exhaust is regular exhaust pipe from a muffler shop. I had them swage the end down to be a slip fit over the tractor exhaust. I have yet to need the generator in the winter so haven't actually run it like this beyond testing it out. The tractor generates a significant amount of heat when it is generating power. Last summer I had been away for a month, got home the night before the power went off for almost three days. I would run the generator in the morning for an hour or so to run the fridge and freezer, run the pump to have a shower and flush the toilet, make coffee then disconnect the generator so I could use the tractor to cut the grass and do other chores. I'd power the house again in the evening for an hour or so. That seemed to be enough to keep everything happy. I only have one tractor, seems like that is still enough. All told during the power outage I don't think I can atribute more than five hours run time to driving the generator so I'm not very worried about wearing out my tractor making electricity.

Thanks, nice idea, simple and sweet.

 

[Charlesaf3]

A PTO generator requires 2 hp at the pto for every kw...ie: a 15 kw generator requires 30 hp at the pto.

True of course. But you do get an advantage even if the generator is too big for the tractor, as I understand it - starting/surge amps and flywheel/inertia effect.

Which the well pump people should think about. That initial surge on motors matters

 

[Charlesaf3]

That's locked rotor amps! What happens when you lock a rotor on a motor? You blow the breaker! It's not the same as starting amps.

Motor Calculations | NEC content from Electrical Construction and Maintenance (EC and M) Magazine

" Motor locked-rotor current. If the rotating part of the motor winding becomes jammed so it can稚 rotate, no counter-electromotive force will be produced in the motor winding. This results in a decrease in conductor impedance to the point that it痴 effectively a short circuit. What痴 the result? The motor operates at locked-rotor current, often six times the full-load ampere rating, depending on the motor Code Letter rating [430.7(B)]. This will cause the motor winding to overheat and be destroyed if the current isn稚 quickly reduced or removed."

Electrical Motor Calculator

Plugging in 1 hp , 90% efficiency, 85 PF (power factor) and 230V to the calculator in this link.

You get:

1 phase = 4a.
FLA = 5A

What does FLA stand for? Full Load Amps! At full load the motor draws 5A, 230V * 5A = 1150W; 1 HP = 746W FLA for a 1 HP motor = 1150/746 or 1.54 times.

Now look at the chart for starting amps, what does the FLC state? 150% to 300% of running current and what's 300%? It's 3 times, exactly what I said. I work with this stuff everyday my systems are built on these calculations. Are you off the grid running several inverters on a daily basis?

While understandable, I'm afraid this is somewhat incorrect. A number of motors draw their locked rotor amps for a short time period at start up. Classic and common example is heat pumps. It's also true of some table saws, which has caused me joy over the years. My sawstop wired at 120 regularly trips the 20a breaker - surge is briefly 80 amps, per the engineers at the factory. Milliseconds, but still would stall out with a little 5k generator.

You can get around LRA with thoughtful staging of equipment starts - I have 3 HVAC units, and I bring them up big to small. But LRA is written on the plates for a reason (note, this is a purported advantage of inverter drive HVAC, no LRA issues)