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Old 30-07-2020, 04:46   #61
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Re: Electrical Fire - Seeking Help Please

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Sorry, do not agree. Fusing must be with 7" of power generating source. The battery switch is almost always further than 7" from the battery.
Yes, No starter current is in the battery charger wires. but in this case the starter is NOT connected directly to the batteries. The switch is wrongly being used to switch batteries to the starter, alternator, panel and charger. Probably why there is a large amperage fuse or no fuse at the batteries.
Yes, a fuse must definitely be at the battery end. But what size fuse? Probably 80 or 100amp because an alternator can push that amount of current into the battery. The fuse is sized per the wiring size and protects the wires. At the panel there is another set of fuses to protect the smaller wires going to the consumption devices.
So what about the battery charger. Typically rated at 20amps for a small boat with appropriate wire size. The battery fuse will not protect the wiring to the charger unless the amps are greater than 80amps or more. In this case we are relying on the current limiting of this charger which should protect the wires against a short between the charger and batteries. In this case the short was in the battery charger, the charger was not working, the current was flowing backwards along the wires and the charger current limiting circuitry did not protect the wires. The current created by the short is dependent on the resistance at the short, the extra resistance caused by heated wires and the capacity of the battery. So an 80amp or larger fuse at the battery will not protect 20amp wires from causing a fire unless the current is higher than 80amps. The most dangerous fires are caused by shorts that generate heat but don't trip fuses. Thats why proper fuse and wiring sizing is extremely important.
Not quite right in this situation. Each segment of wiring has to be appropriately protected. OCPDs (fuses, circuit breakers) are commonly in series as the wiring size is stepped down. Think about what your main panel does. There is an OCPD near the battery supplying power to your panel which contains a bunch of OCPDs for individual circuits on lower capacity wiring. Because the 1-both-2 switch powers the engine starter motor it is not protected. However for downstream loads the switch is the power source. It is totally correct to fuse lower capacity wiring at the battery switch.
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Old 30-07-2020, 05:03   #62
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Re: Electrical Fire - Seeking Help Please

@Jack C #59 You understand the concept but your understanding of some of the details is flawed.

Quote:
Fusing must be with 7" of power generating source. The battery switch is almost always further than 7" from the battery.
And that is why there are two exceptions to the 7" rule. OCPD must be within 40" of the attachment point if the attachment point is not the battery (switch) or within 72" if the attachment point is the battery. In both cases the conductor must be physically protected with sheathing, enclosure, etc.

Quote:
The switch is wrongly being used to switch batteries to the starter, alternator, panel and charger.
This is a standard way of using the ON/OFF/BOTH switch. Nothing incorrect.

Quote:
Yes, a fuse must definitely be at the battery end. But what size fuse? Probably 80 or 100amp because an alternator can push that amount of current into the battery.
You are correct, OCPD is installed to protect the conductor based on the conductor's ampacity. OCPD at the battery is sized to protect the relatively large cable supplying the battery switch. All conductors being supplied from the switch, with the exception of the starter circuit, need to be protected with an appropriately sized OCPD. And therein lies the issue with older boats and the method in which they were wired. With the alternator output sharing the same conductor to the source (via the switch) as the starting circuit, it is difficult to appropriately protect both circuits.

Quote:
So what about the battery charger. Typically rated at 20amps for a small boat with appropriate wire size.
I do not remember the last 20A charger I saw on a boat...they are considerably larger in my market area.

Quote:
The battery fuse will not protect the wiring to the charger unless the amps are greater than 80amps or more. In this case we are relying on the current limiting of this charger which should protect the wires against a short between the charger and batteries. In this case the short was in the battery charger, the charger was not working, the current was flowing backwards along the wires and the charger current limiting circuitry did not protect the wires.
An OCPD at the battery or switch end of the conductor, sized to the ampacity of the charger output conductor would certainly have protected that conductor from a short circuit.

Current limiting is a designed in function of a charging source and has absolutely nothing to do with this casualty as the charger was not in operation.

Quote:
The current created by the short is dependent on the resistance at the short, the extra resistance caused by heated wires and the capacity of the battery. So an 80amp or larger fuse at the battery will not protect 20amp wires from causing a fire unless the current is higher than 80amps.
There were apparently no fuses in the circuits in this casualty. You added the fictious 20A and 80A fuses to further your argument.

Quote:
The most dangerous fires are caused by shorts that generate heat but don't trip fuses.
No, the most dangerous fires are caused by circuits with inadequate or no OCPD.

Quote:
Thats why proper fuse and wiring sizing is extremely important.
And on this, we agree!

It is important to note that inverters, inverter/chargers and chargers are all required to have a case ground connected to the B- bus to help mitigate an internal failure in one of these devices. 75-90% of the boats I work on do not have a case ground installed.
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Old 30-07-2020, 05:28   #63
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Re: Electrical Fire - Seeking Help Please

Charlie, my concern is that similar fires or worse can occur on boats having the same wiring design and charger.

As a professional, a AYBC Master Technician looking at this or similar installation, what would you suggest should be done to eliminate the danger of fire and why?
Help these folks and maybe save lives.
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Old 30-07-2020, 05:45   #64
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Re: Electrical Fire - Seeking Help Please

@Jack C #63
Simply follow the rules, they have been written as the result of property damage, personal injury and even death. Primary to the discussion at hand is that (See post #51) every B+ conductor, with the exception of the starting circuit, must be protected by an OCPD sized to protect the conductor.

BTW, there is a serious discussion about adding OCPD to the starting circuit.

Regarding the, probably missing, case ground, RTFM...Read The Freak'n Manual. Every techman for marine rated inverters, inverter/chargers and chargers that have metal components, requires a case ground back to the B- bus. This is really in place to ensure that an internal fault to ground in the equipment will have a redundant, low impedance path to B- so that the DC fault current (battery driven) is not attempting to use the AC cable (AWG 14/3?) as its fault path to safety ground.
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Old 30-07-2020, 06:07   #65
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Re: Electrical Fire - Seeking Help Please

CharlieJ wrote -

"An OCPD at the battery or switch end of the conductor, sized to the ampacity of the charger output conductor would certainly have protected that conductor from a short circuit."

Very much agree that simply adding an inline fuse where the charger cables connect at the battery switch would have nipped this before there was damage. That leaves the starter current and other loads able to do what they are supposed to. For people connecting the charger directly to the battery terminals, again, just add an inline fuse to each charger cable's connection. Very cheap insurance.

To be honest I'd overlooked it in my own boat so will be adding them. I have a 20A charger with the leads connected to each battery, so will simply add a 30A fuse to each charger cable at the battery end with one of these:

Hope this is a help for others wondering what to do.

CharlieJ wrote -

"Current limiting is a designed in function of a charging source and has absolutely nothing to do with this casualty as the charger was not in operation."

Because you wrote it elsewhere the right way, I'm sure what you meant to say again in this sentence is that current limiting is designed to protect the wire and is sized for the conductor, regardless of what the conductor supplies power to.
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Old 30-07-2020, 06:28   #66
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Re: Electrical Fire - Seeking Help Please

Quote:
Originally Posted by Checkswrecks View Post

"Current limiting is a designed in function of a charging source and has absolutely nothing to do with this casualty as the charger was not in operation."

Because you wrote it elsewhere the right way, I'm sure what you meant to say again in this sentence is that current limiting is designed to protect the wire and is sized for the conductor, regardless of what the conductor supplies power to.
No what he was saying is the internal current limiting capabilities of the charger itself is not a substitution for a proper OCP for the wiring.

People sometimes see oh this charger (or other device) has a current limiting capability so I don't need a fuse on the branch circuit. No you still need a fuse. The purpose of the fuse is to protect the wiring from excess current.

Quote:
To be honest I'd overlooked it in my own boat so will be adding them. I have a 20A charger with the leads connected to each battery, so will simply add a 30A fuse to each charger cable at the battery end with one of these:
Which is why it is good the original author shared the story. There are thousands of boats with the same lack of protection on the charger circuit.
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Old 30-07-2020, 06:51   #67
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Re: Electrical Fire - Seeking Help Please

Charlie, where can we read the rules? ABYC? Perhaps you can help us all who can't afford an ABYC subscription to read the rules. Any suggestions? Must we pay ABYC or ABYC techs to stay safe?
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Old 30-07-2020, 07:06   #68
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Re: Electrical Fire - Seeking Help Please

Back to the OP. Turning off the engine would NOT have solved your problem unless you just got lucky. The proper response to smoke (especially burning insulation smoke) is to kill the engine AND isolate the batteries. In this case, turning the battery switch to off probably would not have helped, as the shorted wires were not switched.

I once had a similar problem on a small race boat without an inboard. As the smoke poured out of the cabin on a heavy air beat to windward, I found that the Radio Direction Finder (that dates me) was wired directly to the batteries, with the wire going into a wet bilge. Fortunately I was able to find a pair of pliers and break the red hot wire without burning myself.
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Old 30-07-2020, 07:09   #69
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Re: Electrical Fire - Seeking Help Please

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Originally Posted by donradcliffe View Post
The proper response to smoke (especially burning insulation smoke) is to kill the engine AND isolate the batteries.

And this is why, in my mind, bilge pumps and such bypassing the battery switch is dangerous. If you want to bypass a panel main for those, that's fine, but if I shut down the engines, kill the shore breakers and turn off the battery switches, that should leave nothing energized except the short run between battery and switch. The battery switch isn't a convenience shutoff for leaving the boat unattended, it's an emergency shutoff.
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Old 30-07-2020, 07:36   #70
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Re: Electrical Fire - Seeking Help Please

Quote:
Originally Posted by Jack C View Post
Sorry, do not agree. Fusing must be with 7" of power generating source. The battery switch is almost always further than 7" from the battery.
Yes, No starter current is in the battery charger wires. but in this case the starter is NOT connected directly to the batteries. The switch is wrongly being used to switch batteries to the starter, alternator, panel and charger. Probably why there is a large amperage fuse or no fuse at the batteries.
Yes, a fuse must definitely be at the battery end. But what size fuse? Probably 80 or 100amp because an alternator can push that amount of current into the battery. The fuse is sized per the wiring size and protects the wires. At the panel there is another set of fuses to protect the smaller wires going to the consumption devices.
So what about the battery charger. Typically rated at 20amps for a small boat with appropriate wire size. The battery fuse will not protect the wiring to the charger unless the amps are greater than 80amps or more. In this case we are relying on the current limiting of this charger which should protect the wires against a short between the charger and batteries. In this case the short was in the battery charger, the charger was not working, the current was flowing backwards along the wires and the charger current limiting circuitry did not protect the wires. The current created by the short is dependent on the resistance at the short, the extra resistance caused by heated wires and the capacity of the battery. So an 80amp or larger fuse at the battery will not protect 20amp wires from causing a fire unless the current is higher than 80amps. The most dangerous fires are caused by shorts that generate heat but don't trip fuses. Thats why proper fuse and wiring sizing is extremely important.
If you connect a charger wire directly to the battery switch (as shown), and the wire to the battery, feeding that post on the switch, is larger and protected by a larger fuse, the smaller charger wire to the charger needs to be fused within 7" of the switch stud at a rating that protects that wire gauge. Unfortunately we see this safety guideline violated all the time.

There are exceptions to the 7" rule, (Charlie J. already mentioned them) that can extend this length a bit, but the smaller wire needs to be fused at its source of power, in this case the switch post. We tend to call this the step down rule. Every time a wire coming into a bus, switch panel etc. changes sizes, (like on the battery switch image) that smaller wire must be protected with the appropriate size fuse or breaker and cannot relay on the larger feeder wires fuse..

The battery bank is considered the source of power for overcurrent protection. A Charger, PV system, alternator etc. are all considered a "current limited device" meaning the OCP goes at the battery end of the circuit not the device end. For example a 100A alternator cannot fail and suddenly become a 400A alternator but if the alternator fails internally and shorts to ground the battery bank can often supply well over 10,000A of short circuit current and this is why the OCP goes at the battery end of a circuit. We are protecting the wiring from the battery bank..

The problem here seems to be that the charger installation and ABYC standards were not followed. The charger appears to a be a ProMariner ProTech, a charger that actually had a higher than normal failure rate on our experience. The installation instructions clearly state that OCP shall be installed. If proper installation guidelines are not follow the result can be what we see here..

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Old 30-07-2020, 07:50   #71
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Re: Electrical Fire - Seeking Help Please

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Charlie, where can we read the rules? ABYC? Perhaps you can help us all who can't afford an ABYC subscription to read the rules. Any suggestions? Must we pay ABYC or ABYC techs to stay safe?


Ok first, knowledge and understanding keep you safe. Rules are just written knowledge, intended to guide those who already know this stuff. Just reading the ABYC rules won't turn anyone into an expert.

Second, just about all the important bits of ABYC E-11 (the electrical spec) are available online from manufacturers (eg Blue Seas) and online vendors (eg West Marine). It's also excerpted and explained in several good books on marine electrical systems.

Shorter answer - if you're still concerned about the safety of your boat's wiring, save up $35 and get this book ASAP. And read every electrical chapter. Much more useful to the average boat-owner than having a copy of the ABYC specs.
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Old 30-07-2020, 08:33   #72
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Re: Electrical Fire - Seeking Help Please

Everyone,

First of all thank you to this forum and all the contributors for their help - I appreciate the help (and the well wishes). I'm also very happy that others can learn from this. The boat was built in 1984 and it all seems to be the original wiring (bundled together running in behind the engine I had to install inspection port to get to everything).

Here's an update...
  1. Removed shore charger and all wiring
  2. Removed other damaged wires (refrigeration, AC for hot water heater, B2+ from battery to switch, G from engine to panel, propane switch/valve wires)

Incidentally the G from engine to panel was not fire burned but was chaffed almost through to the wire.

Ideally, with the help of a local professional who I have retained, I will reinstall necessary components (with fuses) to salvage what's left of our holiday and then redo the whole system after we get back.

Thanks again everyone!

Regards,

Andy
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Old 03-08-2020, 08:36   #73
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Re: Electrical Fire - Seeking Help Please

Hi:

1. In the photo of the mounted shore charger, where is the DC negative wire that goes to the engine block ?

2. If you look closely at the photo of the charger with cover off, you can see that the stud at the bottom marked 'NEG' has no wire on it (nut at top of stud). Can also see damage to transformer/ inductor type device above studs (with yellow tape). Also on close inspection, there appears to be 3 fuses (one for each positive output ?) mounted on the printed circuit board between the damaged transformer and output studs.

3. So what happened ?? From what I see, quite sure this is due to a malfunction in the charger that shorted one of the positive outputs to negative. So why did output fuse not blow ?? Perhaps short of positive stud to case.

4. To prevent this in the future, positive leads from the charger should be fused AT THE BATTERY SWITCH END. No need to fuse at charger end since a dead short at this end will cause fuse at battery switch end to blow. The fuse has to be sized according to the ampacity (current carrying ability) of the wire; it is meant to protect the wire. Current ABYC guidelines state that the house batteries should be protected with high amperage devices at the battery end of the cables. Only the cranking motor battery need not be fused.

5. Given the amount of 'collateral damage' to other wire, I would remove most wires and start over. There also appears to be damage to some 120 volt shore power cables. Do you want to do this yourself or get a qualified marine electrician to do ? Should check with your insurance.

6. I am a bit concerned about unconnected blue and orange wires you mentioned. There is a Marine Color Code for wires: ORANGE - Common Feed (fused), LIGHT BLUE - Oil Pressure Gauge, DARK BLUE - Cabin and Instrument Lights, etc.

Good luck !
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Old 03-08-2020, 08:52   #74
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Re: Electrical Fire - Seeking Help Please

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- if you're still concerned about the safety of your boat's wiring, save up $35 and get this book ASAP. And read every electrical chapter. Much more useful to the average boat-owner than having a copy of the ABYC specs.
I would add that Charlie Wing's book is equally valuable.
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Old 03-08-2020, 08:53   #75
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Re: Electrical Fire - Seeking Help Please

Bit late on the thread, but: you said you were underway, engine running, and therefore not connected to the shore charger.

When you stopped the engine, the fire (or meltdown) started to cease without further intervention? Then you should also check your regulator as at that time the only power source besides the solar and MPPT regulators was the alternator.

Not that I doubt that the source of the short circuit might very well be in buried in the shore charger but the regulator might have been damaged as well, and unfortunately also the alternator.

Besides replacing all cables that have been compromised, you should:

a) learn your electrical system inside out so you don't have to confess "no idea what this loose cable is for" - this might be a recipe for disaster. Throw out all wiring that is an idle leftover from previous owners or times.

b) check your alternator (or have it checked) if it still works properly or if by chance the diodes have been wasted. Might be a good point in time to have it rebuilt ;-)

c) check your regulator (or have it checked) - might be toast as well due to the short circuit

d) and unfortunately the same might be true for the MPPT solar controller(s).

While (b-d) do not necessarily be broken you should make sure to check them thoroughly. (a) is dearly necessary.

And finally: think about rewiring, using proper cables, make sure that there is no circuit without matching fuse - where "matching" is a bit above regular load but below wire melting point.
There is only a single circuit that may be without fuse: the hot wire to the starter motor (but take special precautions with dimesnioning and routing the wire). Everything else NEEEDS to be fused.

Triple important - check the connections/connectors. Are they wet, oxidized, or loose? Make sure all connectors are properly crimped and shrinkwrapped.
Check the ring terminals - when stacking them, put the bigger ones down and the smaller ones on top, never stack more than three of them. Keep their mating sides free of oil and grease, and do not use washers except between the terminals and the nut.

And while you're at it, recalculate the loads and check if you are using the right wire sizes for the load on the respective circuit.
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