The Offshore Voyaging Reference Site

Installing a Propane Detector

i just finished installing a propane gas detector with two sensors, one near the stove and the other just aft of the engine where gas would pool prior to kaboom, on our new-to-us J/109.

I settled on the above-pictured unit from BEP Marine. So far it seems like a well-thought-out piece of safety gear.

One of the things I like most about it is that it has no off-on switch, unlike many other detectors, including both of the ones I have owned in the past. Just way too easy to forget to turn it back on.

This is a sensor that should be on at all times when anyone is aboard, so, despite there being a breaker for a gas detector on the panel, I wired it through a fuse and directly to the main positive buss so it comes on the instant the boat is powered up with the battery master switch.

I guess one could argue that it should be on even when the master switch is off, but that would be a significant parasitic drain on the batteries and you gotta stop somewhere.

Also, as soon as the sniffer is off, the gas is off in the locker, too, since this model includes the solenoid control switch.

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Drew Frye

My cat required one in each hull, since there were appliances in both hulls. Obvious.

Don’t forget annual testing. I know you won’t.

Finally, propane sensors are by their fundamental chemistry, prone to certain false alarms … which is not a bad thing. For example, hydrogen from overcharging batteries can set them off if severe and the cabin is very poorly ventilated. Also methane and alcohols. The point is, that if the alarm sounds and the propane is off, there is more likely a good reason than a bad sensor.

Dick Stevenson

Hi Drew,
Good heads-up about pursuing “false” alarms: both in general for any alarm and specifically for propane.
I would appreciate hearing more about the annual testing you refer to.
On Alchemy, every quarter, I direct an unlit flow from a barbecue lighter into each sniffer: never had one fail the test yet, but always re-assuring how quickly the alarm activates.
And every time I change tanks and fill, I pressure test the system, which is easy if there is an appropriately placed gauge built into the system.
I always carry a spare sniffer: not inexpensive but important. On Alchemy I get 4-6 years before they go bad.
My best, Dick Stevenson, s/v Alchemy

Alastair Currie

Alarm management is a subject close to my heart in oil and gas facilities, I audit so called “Critical Alarm Management”. Your post strikes a thought, “the propane is off”. What does that mean in the context of eliminating a source of explosive atmosphere i.e. off could still mean a passing bottle valve. Why do I mention this. Most of the major incidents in the oil and gas industry and many outside, involve justifying that the alarms did not mean what it was detecting. The reasons for that are many, regular spurious alarms, known wrong alarm set points, human frailties et cetera. If your gas bottle is still connected, and it is off, and the alarm goes off, climate the risk by disconnecting the gas bottle, then searching for other sources. Don’t assume gas off, is safe from gas, if the alarm is tripped.

Dick Stevenson

Hi John,
On Alchemy, the on-off switch is the “alarms” circuit breaker on the main DC distribution panel, which is always on-line when anyone is on board. It is protected from inadvertently being turned off by a cover that must be opened before the switch toggle is accessible. Having the alarm activated when no one is aboard to hear never made sense to me.
For years, we had an alarm system where the solenoid in the locker would be shut off if the sniffer sensed propane. It worked well until the sniffer stopped sniffing and turned off the solenoid when in a location where replacing the sniffer was impossible. Living on a boat set up for gas without gas really has its down sides. Luckily, I had enough spare parts to bypass the solenoid and then to run the solenoid by hand with a switch near the cooker. We did replace the sniffer, but never went back to automatic solenoid shut-off.
My best, Dick Stevenson, s/v Alchemy

Alastair Currie

Some sensors are prone to damage from cleaning products and solvents e.g. Pilot type, where the operating manual states that when working with solvents and cleaning products, place a bag over the sensor to protect it. Also, in the Pilot example, they have a life of about 2 years, then need replacing. I have found that around that time, the alarm will not go off when the detector is switched on. Blowing on the sensor works to stop the alarm initially. I always carry a spare gas sensing head. I have my gas system pressure tested annually by a registered gas tester and test the sensor about monthly with an unlit gas lighter venting onto the sensor.

Philip Aston

To aid my paranoia, I’ve added a separate switch so the solenoid can be powered off, leaving the detector on. This is paired the discipline of switching on and off when using the propane, but is no big deal on the rare occasions we forget. Switching it off and watching the flame go out regularly tests the solenoid.

Terence Thatcher

Last year I redid my propane system: new lines,new solenoids, new regulators. I have a stove and a Dickinson propane cabin heater. I also finally bought a battery operated hand held sensor to check all connections. I was shocked to learn how often the sensor revealed small leaks in connections I thought I had well made. I learned to be patient, use sufficient yellow gas line teflon tape, and check every connection a couple or three tines with the gas on.

Wilson Fitt

Hi, John et al,

The propane installation on our boat is now over 20 years old and, in that time, I have replaced the solenoid three times, the regulator two times and the gas detector head once. The solenoids just quit, and the regulators seem to develop little pinholes that let the system pressure drain away and leave a faint propane smell in the gas locker. I think the gas detector should be replaced more often than I have done (they are expensive little things) but the test cycle was always OK.

Last year I decided to replace the supply hose, not because of any indication of problems or deterioration but just on general principles. This involves crawling into small spaces and extensive use of strong language. I bought the new line from a local yachting equipment store, later finding an industrial hose supply house that sells the same thing for significantly less.

This spring I realized that there was a propane leak and eventually traced it to fractures in the jacket of the one-year-old supply hose spread over about a foot just behind the stove. It seems that a single summer season of flexing back and forth every time the stove swung on its gimbals did to the brand-new hose something that more than 20 years of sometimes very vigorous sailing did not do to the old one.

The question, of course is why, and what to do to guard against this in future. I think that the lead of the new hose was the same as the old one and it was not being kinked in the same location every time the boat rolled, but it’s hard to see back there. I have now purchased another new hose from the industrial supplier although he informs me that they are not meant to be flexed back and forth repeatedly, which is exactly what happens with a gimballed stove.

My current solution is to use a separate short piece of hose to connect the end of main run (which is static) to the stove. This will take all the flexing and will be relatively easy to check and replace with a spare if needed, but it introduces another connection in the system, not necessarily a good thing. Apparently, there are hoses with braided stainless covers that are intended to flex but I am not sure that they are well suited to endless bending back and forth in a marine environment. The supplier is checking the specification for me.

So, disaster averted, but it sure got my attention.


Wilson Fitt

Perhaps the hose was faulty, but the failed one, its long lived predecessor and yesterday’s replacement are all “Fairview” branded with embossed approvals of various sorts and attached inspection tags. I think the failure was probably because I did not leave enough slack behind the stove and the wiggling was concentrated on a too-short length of the hose. There is plenty of length now and you know that I will keep an eye out for any sign of pressure loss and inspect the flexing part regularly and carefully, although that is not easy without dismounting the stove. Good news is that I know that the gas sensor works.

We often pin the stove when at anchor but habit has been to leave it swinging underway. The kettle and teapot share their regular home on top so they don’t fly about the small galley.