CNG to propane

DayDreamer41 · Dec 12, 2016

There are plenty of posts on this subject, here is one to get started
http://forums.sailboatowners.com/index.php?threads/cng-cooking-gas.176399/#post-1261185
I read through these post and I did not see the warning, I however see mention of the alarm and flame sensor tied to a burner control valve needed as a safety for propane use. The biggest issue with propane being, it is heavier than air and will sink to the bilge if there happens to be a leak, not a good situation. So on boats which use propane there is a switch to turn the propane solenoid on and a sensor to verify flame is present when a burner or oven is supposed to be lit. As for BTU content, propane contains approximately 1.5 times more Btu's/cf, so in order to convert properly one should change out the orifices on each burner.

Benny17441 · Dec 14, 2016

Yes, CNG is abundant in the US but almost non-existent in other parts of the world. Converting an old CNG stove will not meet Propane safety standards as the CNG stoves do not have thermocouple valves which shut down the gas in case of a flame out. It might not be a big deal but an insurance surveyor could pick it up.

Rick D · Dec 14, 2016

Benny17441 said:
Yes, CNG is abundant in the US but almost non-existent in other parts of the world. Converting an old CNG stove will not meet Propane safety standards as the CNG stoves do not have thermocouple valves which shut down the gas in case of a flame out. It might not be a big deal but an insurance surveyor could pick it up.

Is that true of factory stove conversion kits also?

Benny17441 · Dec 15, 2016

Rick D said:
Is that true of factory stove conversion kits also?

Don't know Rick, you would have to check that out. I'm sure thermocouple switches can be retrofitted but don't know if they are included in the kits or they would have to be purchased as parts separately.
looked around a little and most kits just bring a regulator and jets.

The appliances - ABYC® says .... stoves are required to have a means of securing cookware from sliding and of normal operation when inclined to 30°, oven doors shall be fitted with a latch and be installed in accordance with manufacturers instructions. No fabrics within 27 1/2" of a burner and all other materials within that range must be flame retardant. All appliances must be fitted with flame failure devices (thermocouples). The shut-off (solenoid) switch must be near the stove and be reachable without reaching over a burner. A propane fume detector is required. Other appliances - A CO alarm and oxygen depletion sensor are required if a heater is fitted. Each appliance shall be supplied by a separate regulated supply line that is continuous and originates inside the propane locker. Pilot lights are permitted only in appliances with "room sealed combustion systems"

walmsleyc · Dec 15, 2016

I did a complete conversion from CNG to propane on my Legend 35 a few years back. When I bought the boat, I was able to find places to fill my CNG tank (2 hour drive though), but those places have closed, and I need to go further to find a fill location. The effort became impractical.

I did have to replace the orifices on my stove, but I continued to use my existing stove without any thermocouples. The system is otherwise compliant with solenoids, sniffers, valves, etc. I see that Force 10 (and probably others) sell retrofit burners with thermocouples. My stove is a very uncommon size, and replacing the stove would require a cabinetry reconfiguration. Perhaps I could find a retrofit burner that might fit. For now, I have to rely on the other sensors to detect if the flame blows out.

(for anyone in the area, I have a idle CNG tank and regulator)

Chris

Stu Jackson · Dec 15, 2016

walmsleyc said:
I see that Force 10 (and probably others) sell retrofit burners with thermocouples.

Could you perhaps provide us with a link to where you found that information, please?

walmsleyc · Dec 15, 2016

http://www.downwindmarine.com/Force-10-Burner-Retrofit-Kits-Stainless-Steel-p-91000704.html

Stu Jackson · Dec 15, 2016

Thanks much appreciated.

shawanaga · Dec 15, 2016

Hi Chris I am in Toronto is your CNG tank and regulator up to date with inspections. I just bought my 35.5 this year and I am not ready to switch to propane yet.
Thanks Floyd

Bill Roosa · Dec 15, 2016

Did this a couple of years ago, reused the low pressure regulator from the CNG (the big gray one not the smaller one next to the CNG tank outlet) and a propane quick connect that screws into the regulator input. cost about $5. I did not change out the jets in the stove but did adjust the delivery pressure to account for the difference between propane and CNG. It is the largish flat blade screw head in the "tower" in the center of the regulator. Take off the cap and CAREFULLY adjust (screw in our out) the plastic screw while a helper watches the lit burner till there is the normal blue flame. If memory serves I only had to turn it a turn or two. Mounted the tank on the stern so did not need a container. We are pretty annal about propane so we can get away with not having a solenoid. Did make an extension handle so we did not have to reach down to manually turn off/on the tank.

Benny17441 · Dec 16, 2016

Oh I remember the old days when we strapped a propane tank on deck and ran a hose to the stove in the cabin. We turned the tank valve On to cook and immediately turned it Off when done. The burner was watched the whole time during the cooking process and our nose was the sniffer to protect against hose or stove leaks. Today boat manufacturers are selling convenience and many newcomers to boating do not receive the warnings or training about the use of propane gas.