Propane Solenoids and Risk of Fire
Product reviewed: Trident Marine propane solenoid
First off, propane is a volatile fuel. If incorrectly installed or operated, there is a real risk of fire or explosion. There are advantages to propane that make it better than some marine cooking fuels, and disadvantages, none of which will be discussed in this article. Quick background: I have lived and worked on boats that used propane for cooking for over 25 years, and I currently am an electrician and systems installer. Among other things, I install complete propane systems, including stoves, tanks, solenoids, lines, enclosures, etc.
The main issue we’re looking at today is the heating up of solenoids inside propane lockers. So far, we have only one first-hand reported case of a solenoid actually starting a fire next to a propane tank, but it appears that the solenoids regularly get very hot. The latest install I did was a brand new solenoid, part # 1300-7706.2-KIT, a Trident Marine part bought off the shelf by West Marine. Upon activation, after about 10 minutes of cooking the part heated up enough to burn the skin off a fingertip. For your own reference, try a quick Google search – there are a host of forum items “Is it normal for my solenoid to burn me?”.
After spending some quality time on the phone with Trident, I received the following information:
- A solenoid is a magnetic coil that is activated by feeding it current, which moves a magnet to open the valve to allow propane to flow. This is true.
- All solenoids heat up when in use. This is not true. It is a function of the amount of current flowing through, and how much is converted to waste heat.
- The part was installed correctly - it's just a coil so there's actually no wrong way to install it. Positive and negative 12V can go to the two wire on the solenoid either way. This is true.
- The valve manufacturer (who sells the parts to Trident, who sell the parts to West Marine, who sell the parts to me) says “There is no spark present, so there can’t be any fire” and “The valve doesn’t get hot enough for anything to catch fire”. These are not true. As any electrician knows, electrical insulation can smolder, and fiberglass is a petroleum product and flammable, as is wood and some plastics and rubbers. You don’t need an initial spark to set up conditions for a fire. You just need to melt the insulation off a wire enough so a bare wire can arc.
- After some discussion, we finally established that Trident propane solenoids all get hot when being used. This is true. Confirmed by the company and a survey of recent installs.
- A solenoid can draw up to 6 amps DC when engaged – as much as a good marine fridge. This is true, confirmed with a amp meter. The hotter the solenoid, the higher the draw.
As a side note, there is an electrical principle that applies heat to resistance. The hotter a wire becomes, the more resistance is present in the wire. The more resistance is present in a wire, the more heat is generated. This is how electrical fires start in wires that have corrosion or high resistance, a self-perpetuating cycle of increasing heat until insulation melts off or smolders. ANY extreme heat in an electrical system is undesirable over the long term.
As a science experiment, you can heat up a hot plate or burner until hot enough to burn at a touch (as hot as these solenoids apparently get normally), say 210 degrees. Hold wood, plastic, fiberglass, and electrical wire against it and see what happens. If you actually do this, please take reasonable precautions for ventilation, fire control, and not burning yourself. You get the idea, though – it doesn’t take much to start a smolder, add a little sanding dust or paint, and you have a nice little fire.
So what can we do? Everyone says that solenoids are an important safety item. Even ABYC, which is taken as gospel by surveyors and insurance companies alike, says the following:
A-1.7.3 A readily accessible manual or electrically
operated (e.g., solenoid) shut-off valve shall be installed in
the low or high-pressure line at the fuel supply.
West Marine defines the solenoids as follows in their helpful how-to guides:
Solenoid Control Valves: A solenoid is an electrically-controlled valve that allows you to shut off the gas supply from a remote location. The switch is commonly located on a small panel in the galley area, and has a red light to indicate when the propane solenoid is open. Flip the switch off and the valve closes to shut off the gas. For safety, solenoids close in the event of a power failure.
Some options exist, of course. First off, the safest possible system for managing propane is to turn the tank valve off every single time you finish cooking, making sure it’s always off unless the stove is running. This means an inconvenient trip out to the tank twice every time the system is used, but it makes it so that no propane can leak from your tank into the boat. Period. You could even leave the stove on and burn off the last of the propane in the lines every time you use it to ensure not even a scrap remains in the boat. This is unadvisable though because people have a tendency to forget to turn off the burners if they let them burn out, and when the valve is opened again the burners pour out unlit fuel until lit. This will not impress your surveyor, but is the safest.
Another option is to install a mechanical valve somewhere inline between the stove and the tank, but accessible from inside the boat. This allows propane into the boat (not great) but not into the stove (where most leaks occur) when the valve is off. It’s more convenient, certainly, with a slightly lower safety margin. If you adopt this method, be sure you trust the hoses, the valve, and the connections. I assemble all fittings with liquid Teflon PTFE, and tighten very snug. I also run the lines inside of a chafe resistant sheath to prevent possible puncture or nicks, and all lines are run VERY out of the way, nowhere they could possibly be damaged. The boats I grew up on used this for decades with no issues.
An electrical solenoid is still a desirable item, though. It makes the surveyors and insurance people happy, and provides good safety and convenience. I’m going to be testing out a number of propane solenoids in the future, and will post what results I can here. For now, I am testing the ones I have installed, and removing any that are generating heat.
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