Conversion kit to run MEP-018A on LP

Coug

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I haven't converted one, or seen one of these, but I have worked on other generators that have been converted to run on propane/natural gas.

If the engine wasn't designed to handle NG/LP, a couple things to consider. These fuels are a lot dryer than gasoline is. There will be a little less upper end lubrication due to this (usually not much of an issue) and they might run a little hotter as well. You will also likely see more moisture in the oil if you don't run it for long periods of time as the main byproducts are water and CO2, though this is usually more of an issue in standby generators that run for 10-15 minutes every week or two and don't get run under load often enough/long enough to remove the moisture out of the oil (there is always some blow by past the rings).

The one that sticks in my head the most, 16 years after working on it, was a tri-fuel generator from Northern Tool. Customer was using it as primary power for his workshop. He was running it exclusively on propane.
It was brought in several times while still under warranty. Engine was a Honda single cylinder OHV. First couple times it came in, did valve adjustment. No big deal, valves go out of adjustment over time.
Then it was brought in and valve adjustment didn't take care of the problem. Disassembled the cylinder head, found the exhaust valve was beating itself through the head in an attempt to escape the engine. When fully opened the valve was just coming up to the level of the cylinder head at this point.

My guess from looking at these generators, you won't likely have any of that type of problem as the engine looks to be all cast iron (provided it was built after the era of leaded fuels by several years, as there were a few issues with engines when leaded fuel went away due to not having enough lubrication and valves no longer sealing as the lead build up that acted as a seal burned off).

As long as the kit is adjusted properly then it will likely work as it is supposed to, though I would avoid any kit that requires you to modify the carburetor, and instead look for one that adds the NG/LP mixer to the intake (most likely between the carburetor and the air filter) so you can still run it on gasoline in an emergency.
 

winglift

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Worthington, Indiana
I haven't converted one, or seen one of these, but I have worked on other generators that have been converted to run on propane/natural gas.

If the engine wasn't designed to handle NG/LP, a couple things to consider. These fuels are a lot dryer than gasoline is. There will be a little less upper end lubrication due to this (usually not much of an issue) and they might run a little hotter as well. You will also likely see more moisture in the oil if you don't run it for long periods of time as the main byproducts are water and CO2, though this is usually more of an issue in standby generators that run for 10-15 minutes every week or two and don't get run under load often enough/long enough to remove the moisture out of the oil (there is always some blow by past the rings).

The one that sticks in my head the most, 16 years after working on it, was a tri-fuel generator from Northern Tool. Customer was using it as primary power for his workshop. He was running it exclusively on propane.
It was brought in several times while still under warranty. Engine was a Honda single cylinder OHV. First couple times it came in, did valve adjustment. No big deal, valves go out of adjustment over time.
Then it was brought in and valve adjustment didn't take care of the problem. Disassembled the cylinder head, found the exhaust valve was beating itself through the head in an attempt to escape the engine. When fully opened the valve was just coming up to the level of the cylinder head at this point.

My guess from looking at these generators, you won't likely have any of that type of problem as the engine looks to be all cast iron (provided it was built after the era of leaded fuels by several years, as there were a few issues with engines when leaded fuel went away due to not having enough lubrication and valves no longer sealing as the lead build up that acted as a seal burned off).

As long as the kit is adjusted properly then it will likely work as it is supposed to, though I would avoid any kit that requires you to modify the carburetor, and instead look for one that adds the NG/LP mixer to the intake (most likely between the carburetor and the air filter) so you can still run it on gasoline in an emergency.
Thanks for that thorough reply. This generator will only be used for when the power goes out and this does occur occasionally here in Indiana. There is a conversion kit available for $275 and considering it. The reason that it would be nice, if it worked, is that my house uses NG and the connection to it would be straight forward and of course I would not have to worry about getting enough gas on hand to run it. This particular generator uses a lot of gas. This kit has an adapter that is placed between the air filter hose and the carburetor and apparently has an adapter which would allow you to use propane tanks such as used for RV campers which I also have, so this is very tempting, however I do not want to do something that will permanently harm the engine, so not sure about it yet. I thought that I had seen a post from someone that had done this and was hoping to get some feedback.
 

Coug

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Olympia/WA
Thanks for that thorough reply. This generator will only be used for when the power goes out and this does occur occasionally here in Indiana. There is a conversion kit available for $275 and considering it. The reason that it would be nice, if it worked, is that my house uses NG and the connection to it would be straight forward and of course I would not have to worry about getting enough gas on hand to run it. This particular generator uses a lot of gas. This kit has an adapter that is placed between the air filter hose and the carburetor and apparently has an adapter which would allow you to use propane tanks such as used for RV campers which I also have, so this is very tempting, however I do not want to do something that will permanently harm the engine, so not sure about it yet. I thought that I had seen a post from someone that had done this and was hoping to get some feedback.
If it's for emergency backup, then you will probably be just fine for a very long time. Fuel quality back in the day was nowhere near as precisely controlled as it is now, so a lot of older engines will run on stuff modern engines will crap out from.

The only thing to really be careful of is making sure it gets adjusted properly. You definitely don't want it to be running too lean on NG/LP.

Also, if you have to switch between LP and NG, you will have to do adjustments, as the ones I have seen all tend to be "set it up for one type of gaseous fuel only". LP has more energy density, so you will have to adjust the fuel down on LP and back up for NG. In standby generators they tend to use a restrictor somewhere in the system, a smaller orifice for LP and larger for NG.

Then just make sure that you run it COMPLETELY out of gasoline if it isn't a kit that requires a gasoline start (some kits do allow startup on LP/NG, but I've seen others that require starting on gasoline, then you shut off fuel to the carburetor and wait until it starts sputtering/running out of fuel in the carb before turning on the other fuel source)

If it will start on NP/LG and you are draining the carb/tank of fuel, after you drain it/run until dry it isn't a bad idea to flush the tank and carburetor with something to get residual fuel. Personally I like denatured alcohol. it easily absorbs any moisture that might have collected in low spots, removes the fuel residue (if it isn't too old) and will evaporate off as long as you keep air moving through it (I've used air compressors or even just small blower fans with tubes going into the tank to get it to evaporate. Set it up and walk away for a while). It also absorbs into gasoline and runs through the engine no problems (fewer BTUs than gasoline though, so runs a little lean if that's the only fuel)

You'll want to remove the carburetor bowl to get any remaining fuel out of it as well, and to drain the fuel from the lines and filter as well. Some fuel lines don't like alcohol much, but brief contact with them won't be an issue (even just the bowl off the carb if it can be removed in place, or take the fuel line off and use an air compressor to blow through it until no more signs of fuel should be good)

Or if the manual has it, there are probably instructions for how to prep the unit for storage, just follow all of the instructions for the fuel system portion of the unit.
 

Scoobyshep

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Things to keep in mind:

Natural gas is like any other utility, they can be knocked out due to a disaster (we had it happen one year when a tornado blew a tree down and ripped up a gas line).

Propane, can get expensive, and in an emergency can be difficult to find. I have a civ generator that runs propane or gasoline, and when using propane it sometimes stalls under heavy constant load from the tank icing up from fast fuel flow.


Not trying to discourage you, just throwing a few of the less thought of cons out there so you can make a well informed choice.

Sent from my SM-G950U using Tapatalk
 

Coug

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Things to keep in mind:

Natural gas is like any other utility, they can be knocked out due to a disaster (we had it happen one year when a tornado blew a tree down and ripped up a gas line).

Propane, can get expensive, and in an emergency can be difficult to find. I have a civ generator that runs propane or gasoline, and when using propane it sometimes stalls under heavy constant load from the tank icing up from fast fuel flow.


Not trying to discourage you, just throwing a few of the less thought of cons out there so you can make a well informed choice.

Sent from my SM-G950U using Tapatalk
Right, that was another thing I was going to mention but forgot to.

Depending on the temperature outside, propane will vaporize at different rates.
The more power you need, the more vapor is needed.
The tank has a limited area for the propane to vaporize, especially on BBQ or other portable tanks.
The colder it is, the slower propane vaporizes.

Basic rule of thumb for newer generators is about 16k BTUs per KW per hour.
1 gallon propane is approx 90k BTU.

running a full 10KW will run you 160k BTU, or just under 2 gallons per hour.
Looking below at the tank sizing chart, you'll want to find the absolute coldest your area gets, and size from there. (If your area is above those temps then there are other LP vaporization charts out there, but this at least gives you an idea)

Tank Sizing Chart


For example, if your area gets down to 0F as it's lowest possible temp, then to pull 160k BTUs you'll need at minimum a 250 gallon propane tank, because once you've run it for a day or two and the fuel level has dropped, the 120 gallon tank can't vaporize enough fuel to run a full load on the generator below about 60% fill. (plus larger for more run time is usually better, because propane never goes bad.)
At minimum 20F you can get away with a 420lb vertical tank (100 gallons water capacity, LP tanks only get filled to 80% to allow for vaporization space) While it will work, if you really are running up near max capacity, you'll only have about 2 days worth of run time before you're out of fuel. The 250 gallon tank will give you 5 days approx)

That's usage at full load, at minimal loads you'll still probably burn at least .25 gallons per hour just idling due to the energy used to keep the engine operating as opposed to making power.

If you get an underground tank the vaporization rate will always be at around 50F for vaporization as the ground insulates it from the air and has it's own thermal effect.

Some people seem to have the idea that you can just run a generator off of a bbq size tank and then swap it out when empty. This works on smaller generators, usually under 4kw, but LP doesn't work the same as gasoline because it is stored as a liquid, turns to vapor (at the same time absorbing heat to do so) and then gets drawn through as a vapor/gas. You require a tank at least 7 times the hourly draw rate to prevent everything from icing over.


clear as mud?


Edit: if you have a lot of gas appliances already, you might also need to get the gas company to install a larger natural gas meter for you.
Most residential meters are around 250k BTUs. If you're trying to run a gas fireplace, gas water heater, gas dryer, gas furnace, gas stove, etc, you'll be using anywhere from 100k BTUs on up. An on demand hot water heater can use 200k BTUs on it's own. Not a lot left over for a generator to run on at that point if it's just a 250k BTU meter/regulator.
 

winglift

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Worthington, Indiana
A few questions:
This generator must run at 3600 rpm, with the cowl on which is required for airflow, to provide enough engine cooling. When you speak of adjustments after converting to NG, I assume that I would just need to adjust the mixture and the instructions for that is to adjust until a smooth idle is obtained. Do you think that the mixture is determined by the needle profile and that the performance will be reduced or will this be adjustable?

I plan to provide an outlet for my house NG connection and the idea that I could use the higher pressure Propane tanks seems like a great option if I wanted it for a mobile purpose. There are usually two main reasons for the power to go out here and that is during some severe thunderstorms in the summer and during the winter from downed power lines. It is during the winter, which sometimes gets below 0° F that I wonder about the performance while using NG?
 

Scoobyshep

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Location
Florida
A few questions:
This generator must run at 3600 rpm, with the cowl on which is required for airflow, to provide enough engine cooling. When you speak of adjustments after converting to NG, I assume that I would just need to adjust the mixture and the instructions for that is to adjust until a smooth idle is obtained. Do you think that the mixture is determined by the needle profile and that the performance will be reduced or will this be adjustable?

I plan to provide an outlet for my house NG connection and the idea that I could use the higher pressure Propane tanks seems like a great option if I wanted it for a mobile purpose. There are usually two main reasons for the power to go out here and that is during some severe thunderstorms in the summer and during the winter from downed power lines. It is during the winter, which sometimes gets below 0° F that I wonder about the performance while using NG?

The adjustment would be for fuel to air mixture. RPM must be maintained to keep the frequency right.

switching between natural gas and propane would require mixture changes as they burn differently. natural gas is already piped in as a gas so you wont get the freezing or vaporizing issues with LP.
 

Coug

Well-known member
885
414
63
Location
Olympia/WA
A few questions:
This generator must run at 3600 rpm, with the cowl on which is required for airflow, to provide enough engine cooling. When you speak of adjustments after converting to NG, I assume that I would just need to adjust the mixture and the instructions for that is to adjust until a smooth idle is obtained. Do you think that the mixture is determined by the needle profile and that the performance will be reduced or will this be adjustable?

I plan to provide an outlet for my house NG connection and the idea that I could use the higher pressure Propane tanks seems like a great option if I wanted it for a mobile purpose. There are usually two main reasons for the power to go out here and that is during some severe thunderstorms in the summer and during the winter from downed power lines. It is during the winter, which sometimes gets below 0° F that I wonder about the performance while using NG?
Nor NG performance during the cold, as long as the main regulator is large enough to handle all the loads, then fuel supply shouldn't be an issue.

I don't think you will have much issue with the NG during winter, the only possibility I see is it might be a LOT harder to start. I don't know where the choke is in the system, but I would assume it's built into the carburetor. Adding the natural gas assembly would (usually) be before the choke, so you would likely either have to use gasoline to start it and run it until it's warmed up, or do some type of inlet air restriction yourself or starting fluid (this is one case where starting fluid isn't necessarily bad, just don't use too much)

You might also lose a little bit of engine power running it on NG/LP (more loss with NG) so were it me I would expect to treat it as an 8kw generator on NG and if I can get more out of it that's a bonus.
Adjusting at idle/no load is usually a starting point. Not every unit ends up drawing the exact same ratio of fuel to air at all RPMs/load levels, so get it adjusted at idle/no load until it sounds good, then put a good load on it (5-7kw probably) and check again. It should be good, but might need tweaking.

Usually adjusting these things is finding where it is smooth, then adjusting both ways until you hear it sound a little rough, and find the middle point. Then do the same thing under heavy load and see if it's the same or close. Make sure to do this adjustment with the engine at operating temperature for best results.
I personally like adjusting them just a little on the rich side, but still inside that smooth area.


One thing to add, most of the standby generators have a small tank for the fuel to accumulate in just before the regulator. This keeps plenty of fuel available if a heavy load or whatnot gets dropped on the generator before the fuel in the lines is flowing fast enough to keep up. What I've sometimes seen on units that don't have that accumulator type tank is in the fuel line just before entering the generator is the pipe gets sized out from 3/4" or whatever size it is, up to 2" for 12-18 inches to act as an accumulator.
Think of it this way, carburetors have a bowl under them to act as a reservoir for changing demand. The 2" section of pipe would do the same thing, store a little extra fuel close to where it's being drawn out to keep up with sudden demands until the bowl gets refilled. Fuel injection and diesels are usually under a lot more pressure to begin with so not an issue, where carburetors use atmospheric pressure to feed in fuel
 
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