# Convert Propane Small Engine to NG?



## DWooderson (Feb 1, 2010)

This is the closest category I could find, I hope it's ok to post this question here.

I bought a small dual fuel-power invertor/generator to run my HVAC fan motor in emergencies. I bought the dual-fuel since propane is more stable than gasoline over time. 

I've read that it's possible to convert propane small engines to NG. Conveniently, I have an NG outlet in the back yard with a flex line (gas grill), so this is very appealing to me. 

Can anyone tell me what's involved in the conversion? How do I actually do the conversion? 

For reference, this the invertor (has not arrived yet): https://www.amazon.com/gp/product/B08JRVLB7C/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

Thank you!


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## raylo32 (Nov 25, 2006)

I have a Yamaha inverter generator that I converted to tri-fuel (gasoline, propane, nat gas) using a kit from the the guys at the link below. I run it off a natural gas tap I installed on my outside lower deck... sounds similar to what you have. These guys make kits for many different generators. Give them a try. There are a few other vendors who do similar but this is the only one that I have experience with. The kit I got was comprehensive and the directions were good. I am not sure what difference there is between nat gas and propane, except maybe the regulator since the carb must already have the propane spray bar. If so, maybe they have a way to do just that part.

Generator Conversion Kits to Propane and Natural Gas. (propane-generators.com)


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## HotRodx10 (Aug 24, 2017)

I suspect the conversion would be from propane to *compressed* natural gas (CNG), for an engine that can also run on gasoline. Edit: It appears I was wrong, according to the link from raylo32. I would be concerned about a loss of output capacity with the generator running on low-pressure NG. The statement on the website that "We have never had a complaint about power loss with any of our kits." is not very reassuring. I would want to see at least some test data showing the output capacity before I spent over $200 on an adapter.

Just FYI, according to the specs, it will run 7 hours at 50% load on the 1.1 gallons of gas. Propane MPG equivalent is about 73% of gasoline for car engines, so probably similar for this engine. That should give you over 25 hours of runtime on 4.5 gallons of propane (typical "full" 20lb tank).


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## raylo32 (Nov 25, 2006)

My 4500 W unit with like a 375cc Yamaha engine runs fine on natural gas... although can't say I have ever run it fully loaded.... nor will I need to.



HotRodx10 said:


> I suspect the conversion would be from propane to *compressed* natural gas (CNG), for an engine that can also run on gasoline. Edit: It appears I was wrong, according to the link from raylo32. I would be concerned about a loss of output capacity with the generator running on low-pressure NG. The statement on the website that "We have never had a complaint about power loss with any of our kits." is not very reassuring. I would want to see at least some test data showing the output capacity before I spent over $200 on an adapter.
> 
> Just FYI, according to the specs, it will run 7 hours at 50% load on the 1.1 gallons of gas. Propane MPG equivalent is about 73% of gasoline for car engines, so probably similar for this engine. That should give you over 25 hours of runtime on 4.5 gallons of propane (typical "full" 20lb tank).


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## Oso954 (Jun 23, 2012)

NG jets are typically larger diameter than propane jets. If your mfg did not plan on someone using NG (not typical for a generator intended for the rv market) you will most likely find the engine will not reach full power.

Running lean when heavily loaded, it will most likely over heat.


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## raylo32 (Nov 25, 2006)

The conversion kit for mine didn't mess with any of the existing carb jets. It included a "spray bar" (for lack of a better term) that installed across the throat of the carb intake that connects to a flexible NG and propane supply line that in turn connects to the regulator. So you still have the regular jets to run it on gasoline and the new bar for the other 2 fuels. I don't recall what I need to do to mine to run it on propane since I don't need to do that. But I believe the one spray bar works for both propane and NG and you don't need to disassemble anything to go from one to the other. Could be wrong... The regulator would need to be adjusted for sure and maybe some other stuff. But IDK since I never tried that.



Oso954 said:


> NG jets are typically larger diameter than propane jets. If your mfg did not plan on someone using NG (not typical for a generator intended for the rv market) you will most likely find the engine will not reach full power.
> 
> Running lean when heavily loaded, it will most likely over heat.


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## raylo32 (Nov 25, 2006)

Oh, this is their current website that has search function and better kit info. I don't know why they leave that obsolete web site up. They don't seem to be very web tech savvy, unfortunately.

Home - Motorsnorkel by US Carburetion


The other thing...I just looked at the generator you are buying and I would guess they probably don't have conversion kits for it since it is so small and enclosed. The kits are easiest to install on open frame units or larger enclosed units like mine that have some room inside the case.


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## Oso954 (Jun 23, 2012)

If you are not required to change a jet or oriface somewhere, the mfg usually cuts the running watts listed in the instruction manual For the natural gas usage.

As an example, a Firman 7500 watt tri fuel generator lists the running watts as
Running Watts: 5500 NG, 6750 LPG, 7500 Gas


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## DWooderson (Feb 1, 2010)

raylo32 said:


> Generator Conversion Kits to Propane and Natural Gas. (propane-generators.com)


Thank you Mr. Bill, I understand that the engine in this inverter is a white-label Yamaha, so if that's true, this might be pretty easy. I'll go do some reading at propane-generators now. 

I love the tri-fuel idea.. I could use NG as the primary fuel source, and if that runs out (we're being told that's a real risk in my state of Texas right now), I can fall back on a 40# cylinder of propane. When _that_ runs out, I guess I could siphon gasoline out of our three cars, and hopefully get another 20-40g there.


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## DWooderson (Feb 1, 2010)

Oso954 said:


> If you are not required to change a jet or oriface somewhere, the mfg usually cuts the running watts listed in the instruction manual For the natural gas usage.
> 
> As an example, a Firman 7500 watt tri fuel generator lists the running watts as
> Running Watts: 5500 NG, 6750 LPG, 7500 Gas


Understood. I think that's ok, I know this inverter is relatively small in terms of watts, but the hope is that I will never need to use it, so storage space and cost are factors for that thing I hope to never use. If I _do _need it, my use-case would be running the HVAC blower motor (blowing NG heat), a hot plate, a small-ish microwave, and recharging phones and lights (just one of those tasks at the same time). I also have a small electric heater in case the NG utility fails.


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## raylo32 (Nov 25, 2006)

That's pretty much what I use mine for... refrigerator, the NG furnace, NG water heater (has electronic control) internet (for as long as the provider can keep his stuff running), a few lights and the TVs on antenna. Works like a champ for that. I installed a Reliant transfer panel to make it easy and more manageable. The thing is I got this in 2010 when our local utility was playing loose and fast with not doing maintenance and such and we had MANY outages some as long a 1 week. Wouldn't you know that soon thereafter the state and county came down on them and outages are pretty much a thing of the past.

And LOL... now that you guys got me thinking about this and we have that snow and ice storm coming tomorrow I decided to give mine a periodic test. Wouldn't you know that somehow the starting battery maintainer got unplugged and the battery might be toast. I gave it 10 minutes charge at a 12 amp rate and shifted it back to the 2 amp rate. It looks like it is taking the charge but we'll see. It had been down to 8.5v which probably let it get all sulfated. If it comes to it I can always jump start it or pull the battery out of my motorcycle that I just verified IS on its maintainer.




DWooderson said:


> Understood. I think that's ok, I know this inverter is relatively small in terms of watts, but the hope is that I will never need to use it, so storage space and cost are factors for that thing I hope to never use. If I _do _need it, my use-case would be running the HVAC blower motor (blowing NG heat), a hot plate, a small-ish microwave, and recharging phones and lights (just one of those tasks at the same time). I also have a small electric heater in case the NG utility fails.


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## HotRodx10 (Aug 24, 2017)

DWooderson said:


> I guess I could siphon gasoline out of our three cars, and hopefully get another 20-40g there.


If you buy non-ethanol gasoline, and keep it sealed up, it will keep for quite a while. You can also rotate the gas in cans by emptying it a car gas tank and then refilling the gas cans every few months. 

I filled a couple of (free) 55 gallon plastic drums with ethanol-free gas, and paid $25 for barrel pump, so I have plenty of gas for my generator, regardless of what utilities go down.


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## GrayHair (Apr 9, 2015)

*Fuel* X *BTUs per gal*
Gas SSi 114,000
LNG SSii 75,000
LPG SSii 91,500

Per Wikipedia


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## Missouri Bound (Apr 9, 2011)

I can't imagine the conversion is too tricky.
I have a 7500 watt Generac standby generator that I installed.
It comes with a key that fits into the rear of the unit.
One position is LP, the other is natural gas.
Nothing else needed to be done.
The pressure issue is handled by the gas company. The only difference is natural gas and propane *heaters *is office size.
In fact I would contact your local LP supplier and the natural gas supplier before doing anything. They may have a better direction to lead you.


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## Missouri Bound (Apr 9, 2011)

GrayHair said:


> *Fuel* X *BTUs per gal*
> Gas SSi 114,000
> LNG SSii 75,000
> LPG SSii 91,500


I'm not sure that is accurate.
Natural gas is measured by cu. ft, not pound.
But LP has twice the BTU rating over natural gas per cu. ft.


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## HotRodx10 (Aug 24, 2017)

GrayHair said:


> *Fuel* X *BTUs per gal*
> Gas SSi 114,000
> LNG SSii 75,000
> LPG SSii 91,500
> ...


Per Wikipedia: "Liquefied natural gas (*LNG*) is natural gas...that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. *It takes up about 1/600th the volume of natural gas in the gaseous state...*"

Not really a useful comparison; however, this was useful information:


Oso954 said:


> As an example, a Firman 7500 watt tri fuel generator lists the running watts as
> Running Watts: 5500 NG, 6750 LPG, 7500 Gas


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## HotRodx10 (Aug 24, 2017)

Missouri Bound said:


> The pressure issue is handled by the gas company. The only difference is natural gas and propane *heaters *is office size.


Presumably, you meant* orifice* size. The orifice size is significantly different because the pressure is significantly different. It is not "handled by the gas company". The orifice for an engine, just like a furnace, has to be sized correctly for the incoming gas pressure and altitude. Standard orifice sizes for NG or LPG only work properly at standard pressures at elevations at less than 2000 feet above sea level. At higher elevations, the orifice size should be decreased to derate it for the decreased oxygen.


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## Missouri Bound (Apr 9, 2011)

HotRodx10 said:


> Presumably, you meant* orifice* size.


Yes, that was it.
"Auto-correct is my beast fiend"
It's a shame that auto-correct can spell correctly with out making any sense.
"Handled by the gas company". Well every gas company I have ever dealt with, both natural and LP have installed pressure regulators.
You don't think that is "handling the pressure"?


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## HotRodx10 (Aug 24, 2017)

Missouri Bound said:


> Well every gas company I have ever dealt with, both natural and LP have installed pressure regulators.
> You don't think that is "handling the pressure"?


In the sense that they regulate the pressure in their systems, you are correct. Whether that pressure is correct for a given appliance is not their responsibility; it's the user's. That's where things can get dangerous really quickly.


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## Missouri Bound (Apr 9, 2011)

I think we are arguing the same point.....hence the need for the proper orfice for the fuel being used.
But the gas supplier brings the fuel to their pressure regulator, and the device needs to be equipped with the proper orfices to operate properly.


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