Generator PTO vs Gas Engine Generator

[hobtink]

Butane is more subject to the lower or pressure problem with lowering of temperature, that and leaking Butane was bad about holding in low points during a leak and it has not been used for home use even in the South for 2-3 decades or so for home heating, from what I understand the largest use of Butane now is to raise the octane level of gas to make premium blends and it will supposedly offgas from a tank left in the hot sun after a few days to weeks leaving you with high priced regular octane grade gas. Propane is suppose to maintain the same relative availability as long as there is some liquid in the tank because it boils of to a gas as it is released into you line from the tank, that is not to say that temperature cannot affect pressure, but you are talking about a very modest inches of WC to a few psig, many tanks are below ground. I am in and from the South so I have not experienced su-zero temps. So the only problem I see with any of these fuel and power sources for your generator are several fold; how, where,who and the knowledge to safely connect temp power an return to utility power, putting extra hours on your tractor may affect resale value but a diesel was made to be ran if you don't need or want to maintain another internal combustion engine use your tractor. Need for use of tractor to do other things more than run a gen set but more so keeping tractor RPM setting so that PTO output is within 60 cycles, and the cost per unit of energy generated from fuel consumed and fuel availability versus storage and replenishment. Per unit, NG has less energy than propane to memory and both are costly during the winter as is home heating oil(basically #2 diesel). However, even air cooled engines without oil filtration powered by propane or NG will run clean and long and you don't have to worry about water or soured fuel, varnish separating from gas or paraffin or algae from diesel causing shutdown or loss of power, especially if you do not use something like Lucas fuel stabilizer and run the fuel through the engine to distribute the fuel stabilizer instead of just adding it to the tank, it needs to get into the entire fuel system especially the carburetor / injectors. Diesel can grow algae, and can thicken, Powers diesel additive / lucas fuel stabilizer will also help here. Depending on grade of diesel purchased thickening from paraffin related fuel problems requires more watchful observation of your fuel supply in your generator/diesel tractor and your backup fuel source resulting in a chance of the tractor/generator not starting or running long and the overall cost to operate and value. Also some diesels have areal hard time starring in cold weather. There are several things to consider. Adding a stand alone generator of adequate continuous load wattage, self start, auto transfer loading and un-loading, that runs monthly self tests and is connected to a dedicated and reliable source of propane(large tank) or natural gas generator however expensive if you can afford it will add physical and emotional comfort and security should even prevent frozen pipes in winter and lost refrigerated / frozen groceries in summer not to mention giving cooling AC comfort in the summer. Make a pro's and cons for your use and area and conditions.

 

[TerryR]

In cold weather, the vapor pressure of the propane decreases. This means that, effectively, the tank runs out faster. There will still be liquid propane in the tank, but it will just be sitting there, not vaporizing, and so the lines won't be pressurized. What this means is that if you intend to have 200 gallons of propane to run a generator with, you may need a 400 gallon tank to provide enough vapor pressure to keep the propane flowing.

Thanks, Joshua,

Doesn't the same issue apply to all other uses of the propane? If it were a real issue, how could I use it to heat my home, run the boiler, dryer, range, etc.? I've never seen any issue even after days of near-zero temps.

In any case, I thought large tanks of a size that can reliably supply a generator for an extended period are buried and thus experience limited temperature swing.

Terry

 

[aczlan]

Doesn't the same issue apply to all other uses of the propane? If it were a real issue, how could I use it to heat my home, run the boiler, dryer, range, etc.? I've never seen any issue even after days of near-zero temps.

Yes it does, the difference is that a genset will be pulling at least as much propane as your boiler, dryer and range combined.

Aaron Z

 

[TerryR]

Yes it does, the difference is that a genset will be pulling at least as much propane as your boiler, dryer and range combined.

Thanks, Aaron -

Makes sense - the genset runs on a "high pressure" (10 in. of water?) line, while everything else in the house runs behind a regulator that reduces the pressure (to 1/2 in. of water?). I was told when it was installed that they would have to run a much larger pipe to the genset at lower pressure. At the higher pressure it's a 1/4" copper line.

So, at what outside temps does this really matter? Especially with a buried tank? With a genset sized to start the well pump, freezer, and fridge at the same time, it runs at very light load most of the time. And as someone pointed out earlier, you don't run it 24/7, in our case because of the noise if nothing else. A 1000 gal tank should last a long time, I'd think, even if cold.

Terry

 

[Mickey_Fx]

Mickey,

Why do you see a concern about cold weather and propane?

Terry

Josh pretty much cover the issue but I'll add a couple things. Propane's ability to vaporize is tied to the tanks temp. As you get down to freezing temps vaporization is very slow. Over on Yamaha's web site the do go into the of the details and has charts showing how large a tank is needed at various temps for various sized generators. For a 7kW generator @ 20F, a tank of 400-450 gals is needed to keep up with demand. Surface area of the liquid propane plays a part as well. The tank recommendation was for horiz tanks as they offer the greatest surface area. For max vaporization the tank needs to be half full. Liquid level either higher or lower reduces the surface area and the amount of vaporization taking place.

This problem can be addressed if the tank has a wet leg, thus pulling liquid propane from the tank. The liquid then is moved to a warmer area where is it vaporized and can more easily keep up with the demand. I'm not a propane expert so I don't have any idea how small of a tank can be had with a wet leg.

Don't use propane here and can't justify a large tank for the generator that might be called on one every couple yrs. My larger genny I bought used, Only had about an hr on it. It was rigged for propane. First thing I did was remove the propane setup. Gas tank had never had any fuel in it.

 

[Mickey_Fx]

Thanks, Aaron -

Makes sense - the genset runs on a "high pressure" (10 in. of water?) line, while everything else in the house runs behind a regulator that reduces the pressure (to 1/2 in. of water?). I was told when it was installed that they would have to run a much larger pipe to the genset at lower pressure. At the higher pressure it's a 1/4" copper line.

So, at what outside temps does this really matter? Especially with a buried tank? With a genset sized to start the well pump, freezer, and fridge at the same time, it runs at very light load most of the time. And as someone pointed out earlier, you don't run it 24/7, in our case because of the noise if nothing else. A 1000 gal tank should last a long time, I'd think, even if cold.

Terry

Are you sure about your pressure settings? In an RV the pressure setting is 11-12" water column. Pressure at 12" water column is ~.47 PSI. That's the pressure all the gas appliances run on in RV's.

If you propane tank is buried, the temp variation isn't anywhere near as severe as an above ground tank. Nothing to be concerned about unless you live up N where the ground can freeze several ft deep.

 

[TerryR]

Are you sure about your pressure settings?

Not at all. I was trying to recall what the installers told me 15 years ago, and obviously got them wrong. The low pressure seems to be 10 or 12" of water, so the high pressure line is obviously more, but I don't recall a number for that. That's the pressure on the line from the tank to the regulator that supplies the appliances in the house, and it also goes to the outlet for the turkey fryer and to the genset.

If you propane tank is buried, the temp variation isn't anywhere near as severe as an above ground tank. Nothing to be concerned about unless you live up N where the ground can freeze several ft deep.

The top of the tank is at least a foot deep, and local codes say the freeze depth here is two feet, which is no doubt conservative. The propane dealer put in a 1000 gal. tank, which holds about 2/3 of our annual usage, because he didn't want to try to get trucks up or driveway in the middle of the winter. It's mounted horizontally, so between the large size and the sheltering effect of being well buried, the recommendations you mention suggest we have considerable margin.

Terry

 

[Copperhead]

I had a generac portable unit that did ok. But just picked up a John Deere PTO generator the other day I ordered a couple of weeks ago. 10kw rating mounted on a a nice 3pt platform. Real solid unit. Should work great for standby power and a great unit for getting power somewhere on my property where I need it. The dealer hadn't stocked or had a demand for any of these. When mine showed up, he had it on the main floor of the dealership a few days before I picked it up. He got a few orders for them once others saw the unit.

 

[kateean2]

I'm thinking about the same thing, but also am factoring in that I might want to be off the grid someday.

 

[msch2112]

hi,

i'm thinking of a 25kw PTO generator for my 105hp JD. it wouldn't be used often but there more for long term issues down the road if need be. i don't want to tap into our propane tank because i want that fuel available elsewhere and i'ld probably burn 2 gallons of propane/hr. just how many gallons of diesel per hour would my tractor burn at 540rpm? i've got the 4 cylinder diesel engine.

thanks,

mike