Fire! Lost my Beneteau. Cause?!?

[CharlieJ]

@LakeEffect #6:
Got it...hypotheticals without real context can be problematic to discuss.

[hpeer]

What was stored in your cockpit locker?

Tell us more, in detail.

Were you in a slip, on a ball, or at anchor?

Had you motored at all?

What was stored in the cockpit lockers?

Had they been opened and closed in debarking?

How big a crew and what were each doing?

Electric winches? Where are controls?

Bow thruster and controls?

Windlass and controls?

How does engine exhaust route?

[Garrettw]

Originally Posted by Captain Scott

Came back up and opened the Port cockpit locker and flames came out. (Engine controls are on the Stb Side). Shut that lid then everyone got off the boat and into the dinghy (being towed at the time).

Did you keep flares onboard?

[Howler]

Originally Posted by Garrettw

Sorry to hear but glad all are safe. How is your fuel system routed? For example, my Jeanneau has an aft fuel tank, aft genset and aft fuel/water separator. One time I pinched an o-ring in my fuel water separator and flooded a hidden bilge area under the aft berth with several gallons of hydrocarbons. Consider that the metal fittings and other appurtenances related to your steering gear may have conducted heat from another area.

We too had a fuel leak on a Beneteau 41.1. The gasket on the pickup tube port was cracked and fuel was leaking slowly from that. As with your example, the bilge area under the fuel tank (port quarter cabin) had accumulated diesel fuel several inches deep. That's all been resolved, but the point is Beneteau owners need to be mindful that leaked fuel doesn't make its way to the bilge pump, and just sits there waiting to be ignited! I assume this design choice is based on European Union environmental regulations that make it hard for fuel to find its way into the ocean. Even the overflow valve must have a mechanism that lets air escape, but not liquid. What they fail to realize is the danger this causes, and the fact that a burning / sinking boat will put even more fuel into the Ocean.

If you smell diesel in your aft quarter bilge, I recommend examining with a scope, such as https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1.

To extract it, pour in water and a fuel-emulsifying bilge cleaner, agitate (by sailing) and pump back out using an oil change extractor, for example. Rinse and repeat.

[sinnerman]

On the comments of a fused circuit not preventing an overheat - I agree.

The fuse only prevents an overcurrent, usually in the case of a short circuit or an internal failure generating a high current such as a power supply problem.

If you have a corroded connection which carries sufficient amperage, the corrosion will act like a resistor to the current passing through it and will start to heat. (ohm's law) This heat usually results in the connection's resistance increasing and in turn generating more heat, then higher resistance etc. etc.

As long as the current remains below the fuse's capacity, the fuse is oblivious to what is going on.

The "classic" example of this is corroded shore power cable connections, where the connector will burn and never trip the shore power breaker on the pier...

My two cents.

Cheers

[glenn.225]

You say the boat was in for work. Is it possible someone closed the engine raw water seacock(valve) and the exhaust, not cooled burned through the hose.

[CarlF]

Was there possibly a can of acetone or other flammable solvent in that locker?

I consider acetone too dangerous to store below decks. When I need it, I’ll buy fresh and dispose of any remainder before leaving.

[Kolchac]

Sorry for your loss. Once my bilge hose was clogged (I wasn't on board for a couple*of days) and the bilge pump was working nonstop, the bilge switch was burned. It was not open fire, but in certain*circumstances, it could be. A fuse does not help because the electric current was not changed.
If you have any not fused electrical motors (like autopilot), and the motor was active*and stalled, it might be the reason for the fire.*

[team karst]

Engine was on. Engine area had a exhaust fan? I've seen these fed from the engine/fuse directly, and the wire was not large enough to support a 20A engine breaker/fuse. So, a stalled fan may overheat.

[Exile]

Originally Posted by Lake-Effect

* * *

This is the long way around to say that I don't think that properly-fused circuits cause the majority of electrical fires on boats.

Probably right, at least on the 12/24v DC side. Not sure about the 120/240v AC side but this doesn't sound pertinent to the OP's particular scenario. It did remind me of some conflicting advice I've received from different techs over the years about the necessity of adding in-line fuses to protect wires even in properly fused circuits. In perhaps an overabundance of caution I have done so, for e.g., in my 12v charging socket circuit with long wire runs to the V-berth. Easy enough to do.

The argument I've heard for adding inline fuses is that a circuit breaker won't necessarily trip in the event of a compromised wire or corroded wire termination, even if it results in a fire. This is exactly what happened to me once with my main aircon unit even though the circuit breaker will routinely trip if water flow through the raw water pump gets blocked. Had some sparks flying due to a build-up of corrosion/resistance at a termination point. Again, this is the 120v side with a high amperage circuit obviously, but windlasses & electric winches/furlers have large amp draws on the DC side as well.

A bit off-topic but wondering what others think, and what ABYC might have to say about inline fusing in otherwise properly fused circuits. Sorry to hear about the OP's loss and hope he can get to the bottom of it.

[Statistical]

Originally Posted by Exile

It did remind me of some conflicting advice I've received from different techs over the years about the necessity of adding in-line fuses to protect wires even in properly fused circuits. In perhaps an overabundance of caution I have done so, for e.g., in my 12v charging socket circuit with long wire runs to the V-berth. Easy enough to do.

The argument I've heard for adding inline fuses is that a circuit breaker won't necessarily trip in the event of a compromised wire or corroded wire termination, even if it results in a fire.

If an inline fuse would blow a circuit breaker of the same allowed ampacity would also blow. I think someone was telling sea tales or something got lost in translation.

A bit off-topic but wondering what others think, and what ABYC might have to say about inline fusing in otherwise properly fused circuits. Sorry to hear about the OP's loss and hope he can get to the bottom of it.

The big issue with inline fuses is they don't protect the wire "upstream" from the fuse. So if they are used they should be as close to the busbar or panelboard as possible. They also reduce clarity because now your OCP is all over the boat not organized at busbars & panelboards. It can also lead to situations where assumptions are made. If your routinely use in-line fuses off a busbar then having positive connectors on the busbar unfused wouldn't be obviously wrong until someone accidentally changes something out and doesn't put an inline fuse in. If everything on the positive busbar has a fuse it is pretty obvious when something doesn't.

One limited application of inline fuse would be to share breakers (or fuse/switch). If you only have a single open 10A breaker and need to support a pair of 5A runs you could connect the 10 breaker to it a pair of 5A fuses. Still if you have open spots on the panel it would be clearer (and clarity is a good thing) to just use a pair of 5A breakers.

[Exile]

Originally Posted by Statistical

If an inline fuse would blow a circuit breaker of the same allowed ampacity would also blow. I think someone was telling sea tales or something got lost in translation.

More likely lost in translation. But why then did the circuit breaker for my main aircon not blow when the busbar terminal caught fire (sparks at least)? Perhaps it would have shortly after I almost immediately discovered it and shut it off.

The big issue with inline fuses is they don't protect the wire "upstream" from the fuse. So if they are used they should be as close to the busbar or panelboard as possible.

I was told (I think) to place the fuse (same amperage as the breaker) at the end of the wire run in order to do just that. But if it won't protect the long wire run "upstream" then it sounds useless & redundant.

They also reduce clarity because now your OCP is all over the boat not organized at busbars & panelboards. It can also lead to situations where assumptions are made. If your routinely use in-line fuses off a busbar then having positive connectors on the busbar unfused wouldn't be obviously wrong until someone accidentally changes something out and doesn't put an inline fuse in. If everything on the positive busbar has a fuse it is pretty obvious when something doesn't.

So long as the circuit breakers and wires (edit) are properly sized and in good working order it doesn't sound like there's much if any benefit.

One limited application of inline fuse would be to share breakers (or fuse/switch). If you only have a single open 10A breaker and need to support a pair of 5A runs you could connect the 10 breaker to it a pair of 5A fuses. Still if you have open spots on the panel it would be clearer (and clarity is a good thing) to just use a pair of 5A breakers.

Any downside to the inline fuses I've already installed at the end of the wire runs? (apologies to the OP for the off-topic)

[jsanton]

Hi Captain Scott,
I’m a retired electrical engineer. Although I primarily worked with integrated circuits, I have done safety engineering for high power systems. And I’ve done forensics on many failures, but maybe one fire.
This forum is not a great place to debug the potential electrical problem. If you could somehow setup a phone conference with someone with a very similar vessel, you and I, we could together vet the possibilities.

Breakers and wire are matched. The notion is, if there’s a condition where the wires are required to carry just shy of the rated capacity of the breaker, the wires won’t overheat and create a fire. As others have discussed, that’s a bit tricky to create that situation. But if you do, the max power possibly deliverable to a rogue load is 12V x max current, which is likely 20A. 240W light bulbs are pretty hot. And that heat is generated at the rogue load, not in the wire.

Spontaneous heat generation from rags stored with absorbed petrochemicals is a serious risk that needs to be assessed as well.

Propane leaks are another serious risk on boats.

And of course, gasoline fumes if you carry gas.

There’s also risks if the raw water inlet is plugged. The exhaust hose can heat up very quickly, perhaps melt. I don’t know that technology well, but there may be a fire risk there.

Fortunately, diesel and fumes are an unlikely fire source.

[CaptainMarkS]

Originally Posted by Captain Scott

Great answers! Thanks to all. Now... More background.

And I will answer all the question to this point from others as well in this response. First, a more in depth overview:.

The fire started aft of the engine compartment and both Stb and Pt aft cabins. In the space there is only the autohelm a stern light wire and a wire going to the propane tank. All of these were off at the time. The auto and (on occasion (shown "Low Voltage) when there was NOT low voltage. I am not an electrician, but after reading some of the more indepth electrical scenarios, I though to incude this

One piece of information I did not include was the observations of the captain and crew as the fire progressed.

THe autohelm was not on at the time. Engine had been idling in gear for about 6 minutes as the main was being hoisted.

The first thing was faint black smoke from the pedestal under the center cockpit table. There was and access plate it that pedestal that was off at the time and that is were the the whisps of smoke first came out. Went below and nothing was wrong. Engine compartment was check and no fire there. Came back up with a fire extenguisher and emptied it into that port with little effect as the smoke was increasing. Went back below and there was now smoke in the salon. Came back up and opened the Port cockpit locker and flames came out. (Engine controls are on the Stb Side). Shut that lid then everyone got off the boat and into the dinghy (being towed at the time).

?Fuel Tank/Connections a possible cause?
Fuel Tank was under the aft stb bunk. The Racor, in the engine compartment

?Fused?
It had a breaker switch on the panel. Nothing on the boat survived for inspection.

Sorry to hear about your loss. I'm surprised nobody picked up on your "wire going to the propane tank" data. The tank might have been off (I'm assuming with solenoid vs actual valve). The solenoid might have been downstream from the tank, meaning any flexible hose from tank to solenoid might have had a crack. Flexible hoses are known to crack and should be replaced every 5-7 years. Also, solenoids are known to fail. If the fire were related to a gas leak, one would expect more of an explosive combustion rather than slow build, but who knows... since you're reviewing all options...

[Shrew]

My autopilot is powered when the DC breaker on the panel is turned on. The power on the AP unit is really just for the display, not the AP itself.

Understanding how that system is wired and its actual state at the time would go far to theorizing a root cause.