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Old 03-08-2020, 09:07   #76
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Re: Electrical Fire - Seeking Help Please

Thanks for your reply,

The general concensus here is that there was a problem with the charger. I still have it and will have a closer look later.

All collatorally burnt wires have been removed and some replaced and I hired a marine electrician to answer my questions. I have also done a thorough inspection. Damaged wires include...

1. Shore charger (later) and all wiring
2. AC to HW heater (will not replace)
3. Propane switch wires
4. Sink sea pump
5. Autohelm and anemometer (later)
6. Refrigeration

I also fused the panel and understand ABYC requirements regarding fusing at power sources. We are due for survey next month.

After a solid week of work and about $300 in material we just had our first night back on the water.



Originally Posted by GuySailor View Post

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, 09:45   #77
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Re: Electrical Fire - Seeking Help Please

Just an additional thought - The wire going to the battery switch had melted insulation right up to the switch post. It got really really hot. Metal conducts heat really well which means the battery switch post got really hot. Switches have ratings and the switch probably was rated high enough for current going through it - before the heat.

Switches, and other devices, can lose their safe current rating when they get overheated. I would suggest you at least check the resistance readings of the switch between the common post and both the #1 post and the #2 post. If you get a high resistance (should be very small) you should replace the switch.

I would also tend to not trust other wires and terminals connected to the same post that got overheated. You can have internal damage in the wire to terminal connection if they got too hot. I would do a resistance check for each of the cables that were on the same post. This may be a little anal but I have seen this happen.

I'll just second the opinion to put OCP at both ends of a charger positive output wire, at least any high current devices like alternators and shore power chargers. And, on solar chargers. The solar charger on my last boat could put out 60amps at 12v and I didn't really view that as self-limiting by any means. I put a circuit breaker type OCP rated at 80amps right at the charger so I could isolate the charger from the battery if I needed to do any maintenance, or to replace it. That can be very handy with an alternator since they often don't go through a battery switch.

Electrical fires are one of the scariest things that can happen on a boat so I tended to go over the top. I have seen loose connections cause more overheating than anything else though so just checking connections routinely is a good thing to do.
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Old 03-08-2020, 10:06   #78
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Re: Electrical Fire - Seeking Help Please

Well - that was exhausting. Reading through the responses, I mean. Evidently, folks on this forum do not get out enough (by definition, really). Even someone who will never go deep-sea can learn something.
Protecting power lines at the power source with fuse/breaker ratings suited to the cable ampacity. Sure, splice an inline fuse, however tacky it looks! Aircraft owners ceased using panel or inline fuses a while back - in favor of switch breakers or pull off breakers. Not sure how you would rig those easily near the power source though.
The mention of a regulator short causing over-volt failures brings back bitter memories of replacing 720 channel VHF radio AND transponder - the moral there was shielded wiring is fine and dandy, until the shield touches an alternator sense wire at the regulator. But enough of adding to the hoards of anecdotes, I will leave you with just one thought. A shore charger OR ANY OTHER BOX with a fan will one day have a fan failure. If there is a choice of two boxes, you choose the one WITHOUT the fan.
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Old 03-08-2020, 10:09   #79
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Re: Electrical Fire - Seeking Help Please

"Switches, and other devices, can lose their safe current rating when they get overheated."

Along those same lines, those Perko Battery Switches can have contact resistance problems as they get old. Considering the small cost and that they fit in the same hole, might consider replacing same with a new Blue Sea Switch when you get back to the serious overhaul stage.

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Old 03-08-2020, 10:27   #80
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Re: Electrical Fire - Seeking Help Please

Good point Frankly. Not all battery switches are created equal, especially the offshore made 'Ol Red Battery Switch' of decades past ! Blue Sea switch has tin plating and 3/8 " dia. studs.
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Old 03-08-2020, 11:44   #81
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Re: Electrical Fire - Seeking Help Please

I did not read all comments, so probably I repeat some.
1. Are your battery connected in parallel firmly, as in your picture? If they are - very wrong!
2. The shore charger should be connected to the battery with separate switch. looks like it is connected to batteries firmly. Even if it is not powered, it has some electronics in output, which could be damaged and shorten battery.
3. The alternator has a voltage stabilizer. If the stabilizer is damaged, the output could be much higher than 13 volts.
4. Your picture is not informative. Next time use principal schematic.
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Old 03-08-2020, 13:33   #82
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Re: Electrical Fire - Seeking Help Please

Originally Posted by Kelkara View Post
First of all ... you haven't mentioned fuses anywhere. A fuse wouldn't have prevented this problem from occuring, but it might have prevented the fire that developed as a result. So high on my to-do list would be to check that all wires are correctly fused for next time.
Agreed, you would not have had any overheating or burning wires had these been properly over-current protected (OCP), i.e. fuses or circuit breakers at the source of power, the batteries. OCP should be within 7" of the battery positive post, or sub-distribution point such as a battery switch or bus bar for wires smaller than larger wires connected to these devices. OCP can be within 72" if sheathed, but closer is always better.

You are very lucky, for wont of a $10 fuse and holder you could have lost the boat and more. Was this gear professionally installed?

Literally only minutes ago I completed an article on this very subject. It will be published on my website later this week.

Here's one I'd written previously for the marine industry
Steve D'Antonio
Steve D'Antonio Marine Consulting, Inc.
ABYC Certified Master Technician
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Old 03-08-2020, 13:54   #83
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Re: Electrical Fire - Seeking Help Please

ABYC E11 Standards provide lots of guidance. If you can use a multimeter and correctly terminate wires, you’ll have all the guidance you need to correct the issue and prevent reoccurrence
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Old 03-08-2020, 15:10   #84
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Re: Electrical Fire - Seeking Help Please


Your family and you are very fortunate that the DC short circuit cleared itself when the AC battery charger's negative conductor burned thru opening the short circuit.

Attached is the AC battery charger O&M manual. This AC battery charger has a unique feature: three independent DC outputs. The battery charger does not appear to have been installed in accordance with OEM guidelines.

Also in page 7 you will see a photo of the output terminals. Compare this photo to the damaged charger. You will see that the first positive terminal stud trace to the reverse polarity protection has burned into the output transformer. The negative trace is not burned. The burned first positive output trace and burned output transformer choke are the clues that some part of the first DC output supply failed to a short circuit. Short circuit currents flowed thru the battery connected to this stud and the common negative conductor.
The fuses in the output section are not overload fuses, they are fast acting fuses to protect the bridge semiconductors from damage if the charger is connected to a battery with reverse polarity.

Some recommendations:
  1. Hire a marine electrician to conduct a safety survey of the boat's AC and DC systems. Identify all out of compliance conditions, rank severity and make a plan to mitigate. Eventually you will need to rewire the boat.
  2. Your boat's AC and DC wiring is not marine rated tin plated cable. Rewire with "Ancor" type tin plated stranded copper conductors.
  3. Your boat's ring lug terminals appear to be "automotive style". Use tin plated AMP PDIG style terminals with a mating ratcheting crimper.
  4. Solder seal the conductor to the terminal barrel after crimping.
  5. Limit the number of terminations to a terminal studs to two. Use terminal boards to join conductors.
  6. Add fuses to the output of every DC energy source, and circuit breakers to the output of any AC energy source.
  7. Apply silicone boots over any metal stud terminal to prevent inadvertent short circuits.
  8. Apply dielectric grease to bronze or brass terminals, and battery posts to prevent corrosion.
  9. Support multiple cables to prevent chafe.
  10. Eliminate any unused ring lugs on terminals (starter solenoid terminal).
  11. Replace the 1-2-both off switch with two DC single pole switches.
I hope this information is useful.
Attached Files
File Type: pdf 61210_use_promariner.pdf (1.56 MB, 6 views)
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Old 03-08-2020, 17:41   #85
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Re: Electrical Fire - Seeking Help Please

Originally Posted by APWTryfan View Post
I hope I have provided enough detail – please go easy on me as this was rather traumatic.

My wife, 11 year old daughter, dog and I were 10 miles from land, 30 miles from home with no wind.

I was amazed at how instantaneous the electrical fire was – my wife and daughter were down below and had to go out the forehatch. Fortunately, she was able to get to one of the fire extinguishers (good to have 3 on boat in different locations) and we didn't have to use it.
Andy and Family,

Well done!

Your boat is intact, the damage was isolated and your family and your dog are unharmed.

Personally, I have seen an electrical fire overcome (a big, old cabin cruiser) and burn to the waterline in 45 minutes. Ugh. Because of the united quick action of YOUR crew, that did not happen here.

You've received a lot of helpful input regarding what went on with the electrics so you don't need to hear more.

That said, please do take a moment to pat yourself (and all the crew) on the back - as well as your stalwart bucaneers! (Wife and daughter). Right on!

Cool heads and grabbing that fire extinguisher as well as clear-thinking to escape by the forehatch - all excellent responses! It's clear you have an amazing team in the face of unexpected complications.

As traumatic as this was, you all handled it SUPERLATIVELY! Hope this doesn't dissuade any of the crew from sailing and hopefully you will have some sort of celebration for how well everyone mobilized.

Back in the day, apparently the quote at NASA was, "You, Sir, are a steely eyed missile man!"

Now how do we adapt that for your wife and amazing 11-year-old daughter...? Maybe there should be some sort of special, celebratory ritual...!

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Old 03-08-2020, 18:45   #86
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Re: Electrical Fire - Seeking Help Please

Call an electrician, sorry.

We never had a ground from shore charger to the engine. The shore power cord provided its own ground (the three wires).
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Old 03-08-2020, 18:58   #87
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Re: Electrical Fire - Seeking Help Please

Thank you so much to the OP for taking the time to put together such a detailed summary of a scary event. Thank you to the respondents who provided such thoughtful analysis of the problem. This kind of teaching/learning is invaluable and has inspired me to check my electrical cabling for wear points.
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Old 03-08-2020, 20:04   #88
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Re: Electrical Fire - Seeking Help Please

thanks very much to the OP for photos, schematic, and replying to so many comments. Thanks to the ABYC pro's who answered, and to all the anecdote sharers. I am in the midst of planning a new inverter install so this thread could not be more pertinent.

I take it ProMariner inverters (I was looking at a 2000W model) are not well regarded...
Any opinions on Samlex inverters?

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Old 04-08-2020, 07:22   #89
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Re: Electrical Fire - Seeking Help Please

Originally Posted by barnakiel View Post
One of your wires got converted into a bulb filament.

If the culprit is the shore charger, then this may happen if the wire shorts thru an un-grounded housing (often steel or alloy).

However, to become a bulb, a wire needs to have no fuse along the way.

What happened to the fuse then?

I just installed a new ProSportHD charger by ProMariner.
After reading about this fire, and particularly your response, I was appalled as I saw no fuses in my lines as I installed the device. So I went back and read through the installation manual carefully and found that it is protected by “dual inline waterproof fuses”. Is this kosher? Or should I splice in fuses of my own?
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Old 04-08-2020, 08:19   #90
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Re: Electrical Fire - Seeking Help Please

Originally Posted by AJA View Post
I just installed a new ProSportHD charger by ProMariner.
After reading about this fire, and particularly your response, I was appalled as I saw no fuses in my lines as I installed the device. So I went back and read through the installation manual carefully and found that it is protected by “dual inline waterproof fuses”. Is this kosher? Or should I splice in fuses of my own?

The charger itself may be protected by “dual inline waterproof fuses”... but you still need to also protect the charger wiring from the massive currents possible from the batteries in the event of a short like the OP's.

So you still need a fuse on the charger wires, as close as possible to where those wires connect to the battery, whether it is on the 1-2-both-off switch, or right onto the battery terminals.
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