# Generator questions



## Nimrod (Jun 8, 2010)

I own a piece of off grid land that I plan to build on. I will run solar for powering the house but figure a generator will be necessary for backup and to run the big loads like the welder and shop.

I want to get a generator that will be durable and efficient. My research says an 1800 RPM diesel generator is best for longevity. A generator that is running at near capacity will use less fuel than a bigger one at half capacity so I'm thinking a 5Kw would be about right. Electric start would be nice as I am getting older.

I have come up with an MEP 002A military surplus generator that fits those criteria and I can still find one under a grand. My reservation is that parts may be hard to come by. If you have one that is in running order, and you exercise it regularly, what would break? Can you get the parts that break most often? How hard is it to start at -40? Any other concerns about this model?

Do you know of other gennys that meet the criteria and would be a better option?


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## lonelytree (Feb 28, 2008)

If I were looking for a 5 KW generator I would look for a light tower like the ones they use for road construction. Like these.

http://www.machinerytrader.com/drilldown/manufacturers.aspx?catid=1045

Self contained. Several engines available. Find a make with support nearby. 1800 RPM. Some even have a heater that you can use a hose to warm things up with. 

A friend even put skiis on one and towed it 30 miles with his snowmachine.


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## MichaelK! (Oct 22, 2010)

Nimrod said:


> A generator that is running at near capacity will use less fuel than a bigger one at half capacity so I'm thinking a 5Kw would be about right. Electric start would be nice as I am getting older.


No, not a good idea. Many peices of equipment that have an electric motor will consume 2-3 times their rated power consumption for the first second or two upon startup. I've got a 6kw generator, but I can stall it by running my well pump, and trying to start a jammed electric saw at the same time. Running the generator at half load is much much better on all the equipment.


Nimrod said:


> I want to get a generator that will be durable and efficient. My research says an 1800 RPM diesel generator is best for longevity.


Sure, they're better, but they're also much, much more expensive. What's going to be more reliable, one diesel generator, or three gasoline generators?



Nimrod said:


> Electric start would be nice as I am getting older.
> 
> Do you know of other gennys that meet the criteria and would be a better option?


Make sure you get a generator that can both pull start, and electric start. That way, when your starter motor, or battery fails, you can still pull start it reliably.

The last recomendation I can give you is do NOT order a generator that is mail dropped to your home. Even if you buy it from a box store like Home Depot or Lowes, you can't return it back to the store if there's a problem. For a warranty repair, it will have to be shipped back to the manufacturer. Guess how much that's gonna cost? Your needs will most likely be met with a 6-8 kw generator you can find at the local hardware store. Even Costco has generators that will work for you. Just follow the maintainence schedule religiously, use quality oil, and don't leave old gas in it, and it will last a long time.


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## Nimrod (Jun 8, 2010)

Lonely,

Good call on the lighting generators. I will look into them. Are parts easier to find than the surplus ones?
Thanks.

Michael, 

I like the idea that I get a genny with both electric and manual start. I do have a 3Kw screamer now as backup. I am looking at diesel because the diesel fuel stores almost forever and the diesel gen sets can go continous for up to 40000 hours before major maintaince. 

The surplus gen sets are under rated. A 5Kw really can put out 7Kw on a continous basis and more for peak. I don't think the well pump, freezer, or refridgerator will be running off the genny, just loads I have to put on it on purpose, so I can probably avoid overtaxing it.
Thanks.


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## PorkChopsMmm (Aug 16, 2010)

Nimrod -- I write this to you as someone who has lived for the last year in their offgrid house in Michigan.

I have a few comments...
1) You will need to run the generator quite a bit in Minnesota unless you get tons of sun and/or have a massive solar array that can collect enough sun in winter to fully charge your batteries. In the Spring, Summer, and Fall we have an excess of power produced by our solar panels. In the winter we have gone almost 2 weeks at one point without any sun. As such we have run our generator much more than anticipated. When running a generator every day or every other day to charge your batteries it is important you size the generator appropriately -- e.g. it is efficient as possible but also charges your batteries fast enough.

2) Your generator needs to be sized to match your battery bank. We were using a huge 7KW + construction generator that guzzled gas and was constantly tripping its internal breaker -- limiting the amount of power we could pull from it. We bought a smaller Champion cheap Chinese generator with remote electric start for ~$400 that provides tons more power (because it isn't tripping its internal breaker) and it is much more fuel efficient. We have a relatively large battery bank (225 Amp hours at 48 volts -- 8 6V golf cart batteries) and it charges it relatively fast. If you have a smaller battery bank I would recommend something like a Honda eu2000 or smaller since it is extremely gas efficient and has a large following. You can even add remote start to it if you are enterprising enough. 

3) If you are really going to live offgrid you will be depending on the generator quite a bit -- no sun, something breaks in your solar setup, maintenance, etc. Make sure you have a covered area for the generator where snow will not pile up on it and you can add gas to it protected from the weather. We also took this one step further with our remote start generator. The generator is located 75 yards away from the house and starting it became a pain. With the remote start we can fire up the generator while being inside the house -- important if it is really cold out or raining, etc.

*Edit: *I also wouldn't worry about a gas vs. diesel generator. I burn through gas quick enough that the longevity of the diesel fuel would not benefit me. Plus with the additional cost of the fuel, the generator, etc. I think you could buy multiple replacement gas generators and still come out ahead. If you must go diesel I would recommend a "Listeroid" diesel Lister-type generator. They are very expensive but use little fuel and should last forever.

Feel free to PM me with any questions. This past year has been a great learning experience for me.


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## lonelytree (Feb 28, 2008)

Nimrod said:


> Lonely,
> 
> Good call on the lighting generators. I will look into them. Are parts easier to find than the surplus ones?
> Thanks.
> ...


Light towers are made by many manufacturers. I suggest that you look at your area to see who supports them and what their reputation is. I sold Wacker parts, Lister parts, John Deere parts, Perkins parts. 

Lister parts are high. LPW gen sets are nice, but eat a water pump every couple years. 

The lodge that I frequent got a new Lugger this fall and it is saving them 23 gallons of fuel per day. 16 KW VS 30 KW from a surplus generator. My math is around $3000 a month savings. 

If you have a Caterpiller dealer around see what they have. My Cat dealer (that I used to work at) is selling generators big time. A Perkapiller... Cat branded Perkins, is pretty sweet and if you can depreciate it for business or farm, it may be a sweet deal.


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## JohnP (Sep 1, 2010)

Might want to look into RV gensets also. Like Onan. Built to last and come in multiple choices for fuel. Gas/Diesel/Propane. They're nice and quiet too. Especially since you can mount them in an enclosure with only the bottom needing air flow. Not cheap to work on (parts) but it's fairly rare to need to work on one and if you do, parts WILL be available. I bought a broken one and fixed it for 70 bucks. It was almost 20 years old but parts were still available from Onan/Cummins. I think some/most have battery charging capabilities built in too. 

RE: electric starter. 
I have a 65k (5k run) coleman with a 10HP B&S with no elec start. If it don't start on the first or second pull, I walk away from it.


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## PorkChopsMmm (Aug 16, 2010)

Not to beat a dead horse but I want to reiterate that you should know how much power you need before buying a generator if efficiency is a goal or it is going to be tied to a solar solution.


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## Darren (May 10, 2002)

Longevity: Hawkpower hands down. Not cheap. I've used a Perkapillar and I was impressed. We had a 60kw for a job for the price of a 20KW that wasn't available.


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## Gray Wolf (Jan 25, 2013)

We live off-grid. We have one 10,000 watt generator that we use for the well pump once a week to fill the tank, and when we are in the shop, including welding. That generator is total overkill for charging the battery bank when we don't have enough sunshine. For battery charging we use 'disposable' cheap generators of 3,000-4.000 watts. One of our cheap ones has made it almost 9 years and another a little over two years. I alternate usage and change the oil QUITE often. 

I think that you may want to consider having two too. Saves on fuel and you will want a backup, or two, or three eventually.


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## stanb999 (Jan 30, 2005)

Has anyone tried to reclaim the heat from a generator? It would make running it much more efficient.

An internal combustion engine uses fuel in the following way.

Approx. 30% for motion.
Approx. 30% in friction/block heat.
Approx. 30% exhaust heat
approx. 10% unburned.

If you could retain some or even most of the heat energy it would be highly likely to pay dividends in winter running, Or when heat is needed. The block heat is rather strait forward, A water cooled engine, extracting the heat into your home with a heat exchanger. The exhaust heat would be less efficient but I'd bet you could get half of it without too much trouble.

So you could gain 45% or so in retained heat. If your generator is running at say 10 gallons a day 45% of the heat to your home would be around 600 thousand BTU's enough to heat a modest home on all but the coldest days... Of course then in the depths of winter you would be running it more.


Gas contains less energy. Diesel has more. But the diesel is more efficient. So the "heat" numbers should be in the same ball park for both.


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## Nimrod (Jun 8, 2010)

GW,

Thanks for the input. I have a cheap generator from Y2K that starts on the second pull. That's my back up here where I'm on grid and will be the backup when I'm off grid. I have heard that the quality of the electricity the screamer produces sometimes won't run a battery charger very well. Any experience with that? Is the electricity a 5Kw diesel puts out good enough to run my electronics?

Stan,

I looked at Lister engines as a way to power a genny. Since the EPA banned their import, the price has gone way up so I ruled them out. They are water cooled however. I think you could recover much of the heat from awater cooled engine by running it through a radiator that's located indoors.

PCM,

Thanks for your help. I'm single and will run the fridge, stove, and water heater off propane, a wood burner for heat, and the well pump, lights, and TV off the solar. I want the diesel genny to run the shop and the welder. If I need to charge the batteries, I can use the screamer. Does this make sense to you?


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## Gray Wolf (Jan 25, 2013)

A good (pricy) inverter/charger can handle poor waveform input better than a cheap car-charger. We have a Magnum inverter/charger that works quite well with our cheapies, but one works better than the other. But, yes, as you so cleverly put it, a screamer can have problems running a charger. One of our off-grid neighbors bought what he thought was a very nice 12 kw diesel generator that wouldn't run his 24 volt charger, so a diesel power-head does not automatically a good generator. 

While I don't have one, I understand that one of the new inverter generators will run anything. Perhaps in your case a small one of those and a cheap battery charger might be the way to go? Lots of options! 

Don't forget the big starting surge of your well pump when you are sizing your system and that you don't want to trip it out because you used the toaster at the same time as the well pump or at the same time you are charging the batteries.

Satellite internet, computers and satellite tv --- TV is the biggest power user in our house. 

Add everything up just like everyone says and then double it if you ever plan on having guests who wnat to make coffee while they are drying their hair while you are making toast. And they never seem to turn lights off!

And just to confuse things, you will run the house generator a lot more than the shop one. Where do you want to spend the bulk of your generator money?


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## Jim-mi (May 15, 2002)

Running my Yamaha 2000i for a couple hours to top the batteries is far more efficient than running my bigger gen.
The Yamaha is top dog---yes even over the Honda----for longevity......

The Iota battery chargers are also top dog.


All that said, I still wish I could stumble on a sweet Lister deal......


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## solidwoods (Dec 23, 2005)

If you have a tractor using a pto gen is a good way to go,, it's also portable.
To recharge batteries a small lawn mower engine with alternator is cheap easy.
jim


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## Conhntr (Aug 7, 2010)

Jim-mi said:


> Running my Yamaha 2000i for a couple hours to top the batteries is far more efficient than running my bigger gen.
> The Yamaha is top dog---yes even over the Honda----for longevity......
> 
> The Iota battery chargers are also top dog.
> ...


I have the same yamaha it is a really nice smooth runner. Sips fuel. I use it for the rv and it makes plenty of power to run everything (except ac) and charge the batteries at the same time. I doubt most residential battery banks can handle much faster charging than a 2000 inverter generator will put out


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## stanb999 (Jan 30, 2005)

If your only using a generator for charging batteries. Wouldn't it be more prudent to produce battery charging current? 

Something like a small engine and a auto alternator or two? They produce tons of 14 volts charging current.


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## TxGypsy (Nov 23, 2006)

There was an article in the Mother Earth New's about a guy that had mounted a salvaged car motor to use to charge his batteries. Instead of a radiator he circulated the water through the motor in a closed loop through a barrel to heat the water in the barrel while he ran the motor for the short length of time needed each week to recharge his battery bank.

As far as that goes, there would be no reason you couldn't hook up a lawnmower engine to turn a car alternator for battery charging.

A bit off topic, but I thought of it when y'all started talking about using waste heat. I think the article in MEN was written in the 1970's.


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## Jim-mi (May 15, 2002)

Good--24 vdc--- alternators / generators do not come for cheap

yes you can cobble up a lawnmower-/- alternator noise machine

if your system is 12vdc


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## stanb999 (Jan 30, 2005)

Jim-mi said:


> Good--24 vdc--- alternators / generators do not come for cheap
> 
> yes you can cobble up a lawnmower-/- alternator noise machine
> 
> if your system is 12vdc


Still cheaper than buying a small 120v generator and inverting it. 24v Alternators can be had for 200 bucks. not cheap but not real expensive.


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## TxGypsy (Nov 23, 2006)

I'm not saying it is 'the thing to do', but it is always nice to have alternatives. If you have an old vehicle laying around with a shot transmission, but a decent engine....and you would be interested in using the waste heat for something...this might be perfect. One size does not fit all.


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## Conhntr (Aug 7, 2010)

Hmmm that might not be that bad of an idea. Even a large v8 genenrally wont burn over 1/2 gallon an hour on idle, and you could run several alternators off of one at idle rpm. 

The problem is the majority of auto engines are not designed to idle for long periods of time. I used to drive a tow truck with a ford v10 in it. Anytime i was idling for more than 5 minutes i had a switch that would pull the rpm from 900 up to 13-1400. Supposed to orevent issues from excessive idling. I doubt it would burn much more gas though the throttle is still low.


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## stanb999 (Jan 30, 2005)

Conhntr said:


> Hmmm that might not be that bad of an idea. Even a large v8 genenrally wont burn over 1/2 gallon an hour on idle, and you could run several alternators off of one at idle rpm.
> 
> The problem is the majority of auto engines are not designed to idle for long periods of time. I used to drive a tow truck with a ford v10 in it. Anytime i was idling for more than 5 minutes i had a switch that would pull the rpm from 900 up to 13-1400. Supposed to orevent issues from excessive idling. I doubt it would burn much more gas though the throttle is still low.


A smallish water cooled tractor diesel or even a little four cylinder from a car it really doesn't take that much horse power 15-20 would charge a large battery bank. In fact you would have to be careful not to do it too fast. Batteries don't like fast charging after 80%. You would have to size it and the hp to the charging to your battery bank. Idling wont work because you want the higher rpm for good charging. The alternator is efficient at 50% or higher of it's rated speed so that means 3000 or so rpm.


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## 12vman (Feb 17, 2004)

I use a Harbor Freight 2800 watt generator with a Honda 5 h.p. overhead valve engine (Pull Start) connected to a standard garage type battery charger. (Schumacher Model SE-4020) The gas tank hold roughly 1/2 gal. of fuel. This provides me with a solid 20-22 amp charge @ 12 v.d.c. I fill the tank, let it run until it runs out of fuel. It runs for ~3 hrs. and usually tops my battery off..

What's cool is the charge controller will limit the voltage to the settings that I have it adjusted to. I have a Zantrex C-40 and the LED behaves just like it does when the sun is making power through it. It'll reach the bulk level, set there for an hour and limit to my float setting. Totally automatic! ('cept for the filling/starting of the genny) I need the exercise anyway..  Tried and true. Been doing this for many years..


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## solidwoods (Dec 23, 2005)

Alternators need to be run at a little above engine idle. This is to prevent the alternator from pulling the idle down when it's charging.
If your going to run a bigger than required engine, just use your car and raise the idle up a little.
I'd get the info on how long you will have to run an engine to charge your system on average.
That may help in calculating cost.
jim



Conhntr said:


> Hmmm that might not be that bad of an idea. Even a large v8 genenrally wont burn over 1/2 gallon an hour on idle, and you could run several alternators off of one at idle rpm.
> 
> The problem is the majority of auto engines are not designed to idle for long periods of time. I used to drive a tow truck with a ford v10 in it. Anytime i was idling for more than 5 minutes i had a switch that would pull the rpm from 900 up to 13-1400. Supposed to orevent issues from excessive idling. I doubt it would burn much more gas though the throttle is still low.


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## stanb999 (Jan 30, 2005)

12vman said:


> I use a Harbor Freight 2800 watt generator with a Honda 5 h.p. overhead valve engine (Pull Start) connected to a standard garage type battery charger. (Schumacher Model SE-4020) The gas tank hold roughly 1/2 gal. of fuel. This provides me with a solid 20-22 amp charge @ 12 v.d.c. I fill the tank, let it run until it runs out of fuel. It runs for ~3 hrs. and usually tops my battery off..
> 
> What's cool is the charge controller will limit the voltage to the settings that I have it adjusted to. I have a Zantrex C-40 and the LED behaves just like it does when the sun is making power through it. It'll reach the bulk level, set there for an hour and limit to my float setting. Totally automatic! ('cept for the filling/starting of the genny) I need the exercise anyway..  Tried and true. Been doing this for many years..


20 amps @ 12 volts is 240 watts, for charging due to losses you likely use 300. Even with losses isn't it a waste to run a 5 hp engine that produces around 3500 watts?

You would need about 1/3rd to 1/2 hp or a good weed whacker motor to provide the energy your getting. It would use a cup or two of gas in three hours. Or a fashionable 25 cents a day!


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## stanb999 (Jan 30, 2005)

The point I'm trying to drive home is if your running a generator, You must use all the power it is making or it is off the charts inefficient. With this being the case a home built model, built to the size you need is far cheaper to run than a store bought model built for occasional use, for alternate purposes. In battery charging you never have peak loads, you never have idle loading. The needed load is what it is.


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## 12vman (Feb 17, 2004)

I could zap 'um hard and put the battery charger on "Start Boost" and pump over 50 amps into them but that's a bit harsh. 20 amps is about the average level my panels provide so it works well for me..

It's simple and anyone can do it, regardless of what the math says. I only need to run the genny if I get a long string of cloudy days. I haven't used over 5 gal. of gas so far this winter. My Unisolars do rather well in low light and if I'm careful, I don't need to operate it at all..

Nuthin' is 100%. Simplicity is the goal..


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## stanb999 (Jan 30, 2005)

12vman said:


> Nuthin' is 100%. Simplicity is the goal..



I agree.


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## 12vman (Feb 17, 2004)

On another note.. I don't work the genny to death. I bought it over 10 yrs. ago and never had any issues with it..


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## Gray Wolf (Jan 25, 2013)

You'll need some sort of charge controller if you are hooking an alternator or generator to a small motor.


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## stanb999 (Jan 30, 2005)

Nimrod said:


> Stan,
> 
> I looked at Lister engines as a way to power a genny. Since the EPA banned their import, the price has gone way up so I ruled them out. They are water cooled however. I think you could recover much of the heat from awater cooled engine by running it through a radiator that's located indoors.


I took too long. I was looking at them in 2008, had the cash in 2011.


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## PorkChopsMmm (Aug 16, 2010)

Nimrod said:


> PCM,
> 
> Thanks for your help. I'm single and will run the fridge, stove, and water heater off propane, a wood burner for heat, and the well pump, lights, and TV off the solar. I want the diesel genny to run the shop and the welder. If I need to charge the batteries, I can use the screamer. Does this make sense to you?


Thanks for the explanation.

Being single will help a lot! I am married with quite a few little ones and we use more power than we would like, but I wouldn't trade them for the world.

As an aside, refrigerators are pretty energy efficient and if it is just you I am sure you could swing a fridge/freezer combo off of solar if you size everything right. I am trying to reduce our propane load because it still costs money and if you have 100# tanks like I do I still have to go out in the cold and haul them to get them filled.


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## Nimrod (Jun 8, 2010)

Pork Chops,

I bought a 250 gallon propane tank last summer and hooked it up to the cabin where I am living now. I can call around and find the best price on propane when I need to fill it. Last summer I paid $1.25 a gallon (it's cheapest in the summer). 

Here's what I have done. Big propane tanks have a port/valve that allows the propane companies to remove most of the liquid propane so the tank can be moved. You can buy a valve and hose that attaches to this port/valve and allows you to fill 20 lb. to 100 lb. tanks from the bulk tank. This is the same attachment that folks fill the 1950s vintage propane tractors from. I bought the valve. The hose and small tank attachment are on order. 

When I get the rest of the set up I will be able to fill a 100 pound tank for about $25 worth of propane instead of $75 if I take it into the station. A 100 pound tank, filled to 80%. holds 80 pounds. At about 4 pounds to the gallon, 80 pounds is 20 gallons. Twenty gallons at $1.25 a gallon is $25.

It is hard to buy the valve because the propane companies are opening themselves up to liability if you go into low earth orbit. I have outlined what I have done and know it can be done. The risk is entirely yours if you decide to try it.


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## Jim-mi (May 15, 2002)

Say again . .Do all the big tanks have a "wet leg" . . . .???
And I assume that this valve goes on the "wet leg" . . .??

Any idea where I can buy this valve . . ??


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## PorkChopsMmm (Aug 16, 2010)

Great info Nimrod. Thanks for posting.


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## Nimrod (Jun 8, 2010)

Once again, try this at your own risk.

A sealed tank of propane is liquid propane on the bottom and propane vapor on top. If the temperature and pressure stay the same there is an equlibrium between the liquid and the vapor. For every molecule of propane that evaporates the pressure forces a molecule to condense into liquid. Propane evaporates at -46 degrees so the pressure has to be really high inside the tank to keep the propane liquid. There is a valve on top of the tank that sends propane vapor to the stove or furnace to be burned. It leaves the tank because the propane in the tank is under pressure. There is usually one or two regulators that step the pressure down to less than a half PSI. 

There is also another port/valve on the tank that taps directly into the liquid. The port/valve may be on the top or the bottom of the tank. It may have male or female threads on it depending on the age of the tank. 

The valve is something like a schrader valve on the tires of your truck. You can screw another valve (like the one pictured) onto this valve without opening it so you don't have a leak. Once the valve is screwed on, it opens the valve built into the tank. On my tank it is on top and there is a tube that extends almost to the bottom of the tank. If you hook up to this port/valve the pressure in the tank will force liquid propane out. This is how the propane companies drain the tank before moving it although they use a pump to make the transfer go faster and be more complete. If you hook the liquid output to another tank that is empty the pressure will force the liquid into the empty tank. 

The newer tanks have a bleeder valve you open with a screwdriver that lets the vapor out of the tank being filled. When liquid propane spits out the valve the tank is 80% full. You don't want to completly fill the tank with liquid. A completle full tank could explode if the temperature rises and the pressure goes up.

It is possible to screw this up. If any propane leaks and gets ignited there is a fire or explosion. Propane vapor is heavier than air so it will spread out on the ground. It will ignite if it comes in contact with a source of ignition like a campfire, pilot light, or spark. Don't do this around any source of ignition. Do it on a windy day. The other possibility is that liquid propane and vapor that boiled recently are at -46 degrees. This can flash freeze you in the wink of an eye. Be very very careful. 

I don't know where you get the valve in your neighborhood. I have seen the whole valve and hose assembly for sale on CL but you have to know what the fitting on your tank is to get the right valve. You may find someone to sell you the setup if you say you have an old tractor that runs on propane although I don't know if the fitting on the tractor is the same as the one on the propane tanks. Companies use a similar setup to refill the tanks on propane forklifts but I think the fittings are different. The brand name on the valve is Rego. 

Good luck and remember, if you are caught or killed we will dissavow any knowledge of your actions.

If your tank has the older female threads, this may work. I don't do Fleabay and would rather have brand new. http://www.ebay.com/itm/ws/eBayISAP...1756&item=140933571756&lgeo=1&vectorid=229466


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