Installing an LPG Detector

Emergency bilge pump options, installation and maintenance.

Preventing and detecting onboard gas leaks is very serious and necessary business. Take the time to do it correctly.

There are a number of reasons why liquefied petroleum gas (aka LP or LPG) is such a popular choice for onboard cooking fuels: it’s efficient, relatively cheap, and widely available. Unfortunately, it’s also the most dangerous, particularly in regards to boat installations. One recommendation for all boats that utilize LPG is installation of a gas detector or “sniffer.” Let’s take a look at LPG sniffers—what they are, how they work, and some basic installation tips.

Sniffer 101

An LPG detector is simply an electronic unit designed to detect gas leaks and then alert those onboard. Some sniffers consist of a single unit containing the sensor and alarm circuitry, however, most are sold as a “control package” which includes a monitor/control panel, remote sensor (one or more, depending on the unit) and a remote controlled solenoid on/off valve to be installed at the tank. If gas is detected at 10 percent or more of the lower explosion limit (LEL), it automatically shuts off the solenoid and sounds a visual and audible alarm.

Sniffers are designed to constantly monitor the air for LP gas and should be configured to do so, even with no one onboard. This ensures that those returning to their boat are alerted of a leak prior to boarding (and turning on a potential sparkinducing piece of equipment). Boat owners who leave their vessel unattended for long periods of time should look for sniffer units that provide the option to trigger an external alarm (such as a loud horn or marine strobe) to alert marina personnel or passersby that a problem exists.

Installation

Although you should always follow the manufacturer’s instructions, here are some general considerations for most any LP gas detector installation.

The sniffer control panel should be located in the vicinity of the LPG appliance, but must be operable without having to reach over open flames (a stove top for example).

Power should be provided via an appropriately sized circuit breaker or fuse from the “line” side of the battery switch for the house bank (the one always energized), ensuring the unit is always powered up and on guard, even with the battery switch in the off position. If a circuit breaker is used, it should be separated from the main panel and equipped with a lock or guard (to prevent it from being accidentally shut off).

LPG vapor is heavier than air and tends to “sink and flow” like water, seeking the lowest possible point. With shore installations there’s typically enough air flow to aid in dispersing leaking gas, however, a boat’s hull is essentially a watertight envelope, meaning explosive gases can be trapped in bilges or other low areas.

As such, sensors should be located beside and below appliances (under the stove for example) and at other low areas of the cabin or bilge where fumes are likely to accumulate. If mounted in the bilge, they should be located as low as possible without becoming submerged or subject to bilge splash (a general rule of thumb is three inches above the high bilge water level).

When choosing a sensor location, for the most accurate results avoid areas subject to strong ventilation (open hatches, portholes, exhaust fans, etc.), high moisture, high temperatures and excessive amounts of smoke.

Maintenance

Gas detection systems should be tested on a regular basis as per the manufacturer (monthly at a minimum – weekly if the LPG system is being used regularly). All units have a built-in self test for the internal electronics, which usually also automatically tests the sensor(s) and connecting wires.

Although the sensors and alarm system should be professionally tested annually, they can also be tested by owners using a butane lighter. Simply hold the lighter next to the sensor and press the trigger without lighting.

As with smoke and CO detectors, LPG sensors have a limited life span (typically five years) and should be replaced as directed by the manufacturer for optimum performance of the system.

Finally, while gas detectors are an important part of any LPG system installation, the first line of defense in detecting leaks are sniffers of the organic kind—specifically the noses of the crew. LPG suppliers are required by law to add an odorant to make leaks more noticeable, but just because you can’t smell gas doesn’t mean it isn’t there (the gas can remain after the odorant has dissipated). This makes the correct installation of a gas detector even more important.