How do you plumb a natural gas/ propane combo generator.

[4570Man]

So I got what was a previously seized up house backup generator for free. It’s not seized up anymore but it was previously natural gas powered. I suppose I could go to the mower junkyard and get a gasoline carburetor but propane would be easier. It says it runs on either but there’s no instructions. It has a regulator on the generator but a propane bottle has a lot higher pressure than natural gas does. Do I need another regulator for the propane bottle or just a hose to hook the bottle to the regulator?

 

[RNeumann]

You will need a regulator between the propane bottle and carb that is designed to flow enough to run the engine. Depending on the carb it will either need adjustment and new orifices or just adjustment. Their shouldn’t be an issue with running it off propane- actually you will gain a little power.

 

[4570Man]

Actually it’s rated 8000 watts on natural or 10000 on propane so quite a bit of difference. There already is a regulator on the generator but natural gas is like 3 psi where a propane bottle is more. I don’t know if I need another regulator. I didn’t see any adjustments on the carburetor if that’s even what it is but I didn’t look very hard.

 

[chim]

The regulator that's on it is a demand regulator. It probably wants substantially less than a pound of pressure on the inlet side. I have a propane powered Onan that runs on (LPG) pressure something like 11"WC. Depending upon indoor / outdoor there may be a need for a solenoid in addition to the demand regulator. I'd suggest talking directly to someone who works on this kind of equipment.

 

[RNeumann]

The “typical” propane setup is a regular at the tank that drops the pressure to something like 10psi and a secondary regulator at the generator. You will need to pull the info off the existing regulator but my guess is they aren’t compatible. You are correct in that natural gas is regulated down to about 1/2 psi for residential and light commercial. They can bump that of higher demand commercial applications (otherwise the piping gets too big for the required flow). The solenoid valve mentioned above is a good point. The gen should/typically have one for either propane or natural gas.

 

[4570Man]

It does have a solenoid valve. It’s the round thing on the regulator.

 

[Tractor Seabee]

Can you find some manufacturer info on the parts? They probably have manuals on line or a tech dept to help you. These things are OEM specific even if using a lot of generic parts. The ones I researched had a injector device that by passed the gas carb.

Ron

 

[jaxs]

Propane engine regulators typically have 0 psi outlet pressure. For cold weather and/or more than short intervals of operation,you need a heated vaporizer upstream of regulator. In 60f weather,a 30lb tank will operate a 10-15 hp engine a couple of hours without a heated vaporizer,longer with larger tank and/or warmer weather. You will be very lucky to find a mechanic that know's how to work on nat gas and propane carburation. You can imagine how many propane forklifts, forklift dealers and repair shops are in the DFW metro area. I have never found one that can repair or adjust a nat gas/propane carburation system. They can only throw parts at it until it run's or owner go's broke. Call around your area and ask if they can rebuild and adjust regulators,carbs and vaporizers. I'd be amazed if you find a single place that can. The ginny dealer for the brand in question can order the correct parts and install if you like. If you choose to install them yourself,take some advice,don't even think about tweaking adjustment on vaporizer, regulator or carb unless you know exactly what you are doing. .

 

[4570Man]

Can you find some manufacturer info on the parts? They probably have manuals on line or a tech dept to help you. These things are OEM specific even if using a lot of generic parts. The ones I researched had a injector device that by passed the gas carb.

Ron

It’s a completely different device than the gasoline carb. It’s essentially a tube with a throttle flap and a little nozzle the vapor comes through. I know most forklifts circulate coolant through the regulator to keep it from freezing but this being an air cooled engine I have no idea how that’s supposed to work. This motor has an oil cooler on it. Maybe the hot oil could be circulated through the regulator. I could be wrong with this theory but I don’t think natural gas would present nearly the freezing problem propane does.

 

[Chilliwack Murray]

It’s a completely different device than the gasoline carb. It’s essentially a tube with a throttle flap and a little nozzle the vapor comes through. I know most forklifts circulate coolant through the regulator to keep it from freezing but this being an air cooled engine I have no idea how that’s supposed to work. This motor has an oil cooler on it. Maybe the hot oil could be circulated through the regulator. I could be wrong with this theory but I don’t think natural gas would present nearly the freezing problem propane does.

You are referring to a liquid propane regulator/vaporizer which requires heat input to operate. A generator this is almost always vapour fed. If it were liquid the fuel line will be 1/8 or 1/4 inch and will have a couple turns around the exhaust manifold to provide the heat. For a standard vapour withdrawal unit you rely on the evaporation in the tank which takes away heat. You also need surface area for the propane to evaporate so a horizontal tank is much better than a vertical tank.

There is nothing inherently wrong with propane or Nat gas for a generator but both fuels and especially Nat gas have a much narrower air fuel ratio they will run in so anything that affects the mixture like pressure or vacuum leaks will make it hunt or not start. You will also get about 5% less power with propane over gasoline and 10-20% with Nat gas depending on the BTU rating in your area.

Post a model number and pictures of the fuel system we can surely help.