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ELECTRICAL FIRES

About Boat Insurance. Boat insurance claims are a great way to understand what is going wrong on boats.

Whether it is your lovely new Bay Liner, Beneteau or a Sea Ray, Triton boat or Lund boat the same requirement for looking after your electrical systems apply.

Often after buying your used boat you need to survey and assess your systems. It makes good sense, it is good insurance.

Studying the causes of boat-insurance claims is a good way of preventing the causes occurring. This is something boat insurance companies do all the time.

A report has recently been released based on a study by BoatUS and published in Seaworthy Magazine, which is the only damage avoidance magazine for boat owners and the marine and boat insurance industry in the US. The causes of boat fires originating on board boats is summarized as follows and are based on fire related boat insurance claims:

55% AC and DC wiring and appliances

24% Engine and transmission overheating

8% Fuel leaks

7% Miscellaneous

5% Unknown

1% Stoves


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55% AC and DC Wiring and Appliances

This result is a large number, and not unexpected and I will discuss the electrical breakdowns related to this value. Many who have purchased my books and attended the various lectures and seminars understand my own electrical safety based approach. I am for good boat insurance by planning and installing your systems correctly.

30% DC Shorts and Wiring

The most common cause of boat insurance related electrical fires is directly related to wiring and connection faults. The word "short" needs to be quantified as it is often misunderstood. Short circuits are relatively uncommon and in most cases it is because a positive and a negative cable have been inadvertently connected. This is called a "dead short circuit" and usually blows the fuse or trips the circuit breaker immediately. The other type of short has resistance involved between the positive and the negative or ground during a short circuit event. The best boat-insurance is to regularly check tighten all connections

Bilge Pump Wiring

Bilge pump connections, and associated float switches are commonly located in wet or damp locations. In many cases inadequate insulation and the binding or wrapping of the connections together leads to tracking and short circuits. This often results in excess current and heat causing fires. In cases of malfunctioning float switches the connections are also submerged in rising bilge water causing short circuits. This is also good boat-insurance because if the bilge pump doesn't work your boat is unseaworthy.

Wire Chafe

Where wires touch, or transit over or through conductive metallic materials they frequently move, and this movement chafes through insulation. A short circuit condition occurs when the metallic materials such as an engine, stainless tubing etc create a short circuit between the exposed conductors. Avoid a boat insurance claim by doing regular visual inspections.

Wire Connections

The most common cause of circuit failures are attributable to connections. They may simply fail open circuit and prevent power reaching equipment. In many cases as connections loosen, a higher resistance condition is created. This causes voltage drops and the generation of heat, often causing fires. It also may cause short circuiting to adjacent circuit connections.

12% DC Engine Regulators

This number initially caused some concern, however after consulting with the author of the report I am advised that these were due to regulators catching fire within outboard engines exceeding 100 hp. I have personally not heard of boats with diesel engine installations having regulator caused fires. However, I must tell you that fast charge regulators do create many fire and overheating hazards in the connected or peripheral systems. These are summarized as follows and readers should use caution and observe these when installing and commissioning regulators. The main causes that I have identified you will never see in any caution notices within the installation documentation. I have installed many hundreds of fast charge regulators over the years and this is a summary of situations that I have experienced and that do frequently occur:

Alternator Overheating.

In most cases an overheated alternator simply has a winding failure or a rectifier failure. The alternator then ceases to produce heat as it is no longer generating power. This is often caused by an alternator charging into a relatively large and discharged battery bank for a long time period.

Connection Overheating

In many alternators, the output cable connection is often under-rated for maximum output current. In many cases the original alternator is replaced by a higher output alternator without up-rating the cable or connections. You can check your own by simply placing finger on the main output terminal. You may find it is hot, possibly even too hot to touch, if it is you need to look at up-rating.

Cable Overheating

In many alternators, the output cable is often under-rated for maximum output current. When this is coupled with an engine negative return path to the battery with voltage drops across the various mechanical connection points, problems occur. The maximum current values passing through the under-rated cables cause overheating and the insulation catches fire.

Battery Overheating

Batteries in poor condition and in a relatively discharged condition often get hot under high current charging conditions. Often the greater risk is the generation of hydrogen gas.

Pulley and Belt Overheating

The increased load on single pulley alternators often causes overheating. It is not a cause of fire however the heat travels along the alternator shaft, overheats the bearings and the grease melts out, and the bearing fails. Also the belt may stretch with greater slip and eventually fail.

4% AC Appliance Heaters

These fires are not really electrical and are caused by fan or radiator element type heaters located close to timber or other combustible materials. The heat causes the materials to smolder and catch fire.

4% Shore Power

Shore power fires are almost exclusively found in the shore power plug and socket, as these are exposed to rain and spray. Condensation and salt crystals form a path between the terminals and tracking occurs. This resistive path creates heat and the tracking path starts to carbonize as it burns. Eventually it gets to a point where the current values create sufficient heat as the short circuit level rises, and a fire is caused.

2% Battery Chargers

Battery charger fires are caused by overheating. This in turn is caused by under rated chargers charging relatively large battery banks. The over temperature Klixon type temperature safety switches on rectifier bridges or transformers fail and the transformer windings subsequently overheat. The insulation reaches a point where combustion occurs and a fire occurs. In some cases the DC output cables also overheat causing a fire situation

1% AC Power Surges

I have been unable to define precise causes. A surge within a marina is capable of causing damage and a fire to any connected appliances. Surges may be caused by lightning surges or even network switching surges.

In summary most boat insurance claims can be avoided by good systems design, and good systems maintenance. Check your systems before season start, during the season and after seasons end. About Boat Insurance