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BOAT wrote:I think we need one of those engineer smarty pants types that are all over this site to give us some tips on how to isolate and find issues in wires.

I don't even know what kind of gauge to use to troubleshoot wires!

Should we check every line for resistance? How do you check a line to see if there might be a short staring up? I assume the only way to really check a wire is to put it under load?

Some of us are not really fully educated on this stuff - we figure it's just a matter of the positive going to the positive and the negative going to the negative, but there are a lot of things we can do to help prevent fires? Like what's the equipment ground all about? Is that an AC thing only?

I would do a voltage drop test with a voltmeter to test circuits while under load. You can test a single connection, or the entire boat all at once. Any resistance will cause a change in energy (a bad connection will get hot), that can be measured as a small drop in voltage over that connection, or any circuit, or the whole boat. If you had a baseline to compare to, seems like this would be an easy way to tell if your loads are increasing to the point where you need to look for a problem.
But I'm just a dumbass who uses these tools. Any of you smart guys who designs these things care to weigh in and explain better?

It's really hard to predictively test an electrical circuit for failure because failures are far more likely to be due to human error than anything else. I was an Electronic Warfare Tech in the Navy, and we used meggers and ohmeters in monthly preventative maintenance checks on all of our equipment to try to predict problems, and the testing honestly caused far more problems than it ever found. The modern Navy has dramatically cut down PMS requirements because they've come to this conclusion as well.

Common electrical failures fall into three categories:

1) Shorts, where two wires come into contact through direct contact, because a conductor bridged across them, or because a conductive liquid such as seawater bridges across them. These are almost always the result of accidental events and poor insulation/covering.

2) Heating, Increased heat caused by resistance caused by either overload, wire corrosion, improperly underrated wire joints, or installation with underrated wire. Whenever a wire is damaged, it may still function just fine but will increase in resistance compared to its new state. Resistance = heat, so at the point where damage has occurred the wire will warm up a little. Enough heating and in contact with something flammable this can result in a fire. Common corrosion is a big culprit here, especially in marine environments. Usually it results in melted insulator. This problem is where "random" electrical fires not associated with a specific event come from.

3) Opens, where a wire separates and a circuit no longer functions. These are rarely dangerous, they just cause the common problem of "wtf doesn't this work suddenly?" Opens become an issue when you leave them rather than fixing, and then they reconnect under vibration or compression when you aren't expecting it. But even then, they're rarely dangerous.

Uncommon ones that I'm not going to bother talking about electrostatic discharge (very rare, rarely harmful), electrical wire and lighting strikes (catastrophic, different set of problems), and incorrectly installed equipment that has never worked.

The problem with circuit testing is that it can only predict cause #2, and even then, you have to know the original baseline resistance of every circuit you test. Furthermore, many electronic devices simply cannot be in circuit when the circuit is under test or they will be damaged.

For that reason, the best way to avoid electrical problems in my opinion is simply to follow well established best practices:

1) Keep it as simple as possible. Simplicity is your best friend in an electrical system. I likely have the simplest electrical system of anyone on this board despite having a complex suite of electronics for this reason.

2) Keep it dry. Super obvious, enough said. My boat & bilge are bone dry, always have been, always will be. Anything that causes a wet boat should be repaired rather than just lived with in my opinion.

3) Use proper, industry standard methods of joining your circuits, such as solder, proper crimp connectors, and screw terminals. Wire Nuts should be avoided for permanent installations in my opinion, but they are certainly better practice than simply twisting and taping wires. Use plenty of electrical tape to insulate everything.

**crimps and wirenut connectors are a very common source of problems. If they are loosely installed or two small for the current capacity, they cause circuit resistive heating. The best way to avoid this is to solder, even if you crimped first. Solder will increase the area of the joint to match the wire or larger, while crimps are always smaller. Get a battery powered pencil-type iron and solder and keep it aboard in your electrical repair kit. **

4) Cover your battery terminals. I'm guilty of not doing this can gave myself a nasty jolt last time I was adding a device.

5) Use a complete power disconnect. I have my boat separated into two busses: "In Port" and "Underway" with a 1+2 blue heron (perko type) switch.

I do have my engine wired directly to my (single) battery because you should not run an alternator without a battery connected. It's hard on the alternator and can cause it to burn out, causing the very problem that an isolation switch is put in-line to solve. It also allows me to start the boat without going below to power anything on. But all other electronics are disconnected at the switch when the boat is powered off, and the circuit to the motor is a simple pair of fused high-current cables, so there's very little to go wrong.

Use best practices when you install, take the opportunity to inspect whenever you have things opened up, and try not worry about it since testing won't reveal much.

mastreb wrote: For that reason, the best way to avoid electrical problems in my opinion is simply to follow well established best practices:

1) Keep it as simple as possible. Simplicity is your best friend in an electrical system. I likely have the simplest electrical system of anyone on this board despite having a complex suite of electronics for this reason.

2) Keep it dry. Super obvious, enough said. My boat & bilge are bone dry, always have been, always will be. Anything that causes a wet boat should be repaired rather than just lived with in my opinion.

3) Use proper, industry standard methods of joining your circuits, such as solder, proper crimp connectors, and screw terminals. Wire Nuts should be avoided for permanent installations in my opinion, but they are certainly better practice than simply twisting and taping wires. Use plenty of electrical tape to insulate everything.

**crimps and wirenut connectors are a very common source of problems. If they are loosely installed or two small for the current capacity, they cause circuit resistive heating. The best way to avoid this is to solder, even if you crimped first. Solder will increase the area of the joint to match the wire or larger, while crimps are always smaller. Get a battery powered pencil-type iron and solder and keep it aboard in your electrical repair kit. **

4) Cover your battery terminals. I'm guilty of not doing this can gave myself a nasty jolt last time I was adding a device.

5) Use a complete power disconnect. I have my boat separated into two busses: "In Port" and "Underway" with a 1+2 blue heron (perko type) switch.

I do have my engine wired directly to my (single) battery because you should not run an alternator without a battery connected. It's hard on the alternator and can cause it to burn out, causing the very problem that an isolation switch is put in-line to solve. It also allows me to start the boat without going below to power anything on. But all other electronics are disconnected at the switch when the boat is powered off, and the circuit to the motor is a simple pair of fused high-current cables, so there's very little to go wrong.

Use best practices when you install, take the opportunity to inspect whenever you have things opened up, and try not worry about it since testing won't reveal much.

Good advice.

I'm guilty of not covering my battery terminals. I will now after reading this thread.

I have also learned not to cheap out on tools.
Use a REAL crimp tool that ratchets. Not a glorified pair of pliers. Big difference in the quality of the crimp.
Use REAL electrical tape. Scotch Super 33+ is my preferred. Sure, you can buy 12 rolls of "electrical tape" at the dollar store or Harbor Freight, but it's junk, won't stick well and has poor insulating, temperature and water resistance qualities. Toss that other stuff out.
Use stranded marine grade wire. If not marine grade, at least stranded. Solid core wire will fatigue and crack with vibration causing "opens" as Matt described above. High amperage opens can cause arcing and/or heat build up.


--Russ

Okay, I will do that stuff that matt and russ said to do - I never even knew about covering the battery terminals.

I don't want a fire - it's too scary.

Good points above.

When I got my (optional) 2nd battery it came with screw terminals, which were used for the connections, plus the normal lugs, which were bare and unused. Having the lugs exposed bothered me for the above mentioned reason, (or anything, a wrench, screwdriver shorting) could so I capped them with the covers they ship new batteries with which I had kept from a previous battery purchase.

Since the caps are colour-coded, black and red, I have found I get the added benefit of never having to worry about getting the polarity wrong, even in dim light where the small “+” and “-” can be hard to distinguish. A time saver when repeatedly connecting the charger to them at intervals during the winter season, and it reduces the chance of a mistake.

Another best practise when wiring a boat is to connect the fuse in a circuit as close to the battery as possible. The length of wire that runs between the fuse and the battery is unprotected by the fuse from a dead short, so the shorter it is, the “safer” the circuit will be.

I switch my Perko switch to “OFF” whenever I am not present on the boat. It's the 12V master switch on my boat. The shore power stays “ON” to run the fridge and the battery charger whenever at the dock, whether I'm there or not.

-B.

Speaking of shore power (which I don't have--too complicated ), my Sister's Cheoy Lee 65' Trawler burned at the dock in Alaska due to to a short they traced to being inside the refrigerator and caused by a condenser leak or condensation. They'd bought the boat used and didn't do the install, but the problem was entirely inside the fridge at first.

It wasn't a total loss due to the size and cost of the boat, but its still being repaired 12 months later. They had to repair some stuff on the dock as well.

Her experience is the primary reason I don't do anything that requires constant power aboard.

If you don't have the terminal post covers, you can use "Sugru" (from Sugru.com) to form a cap over them. You can even buy it in red and black. It's waterproof silicon rubber that forms a hard part after 24h of exposure. Check out their website, it's super useful stuff.

I'd just like to say - I'm damn glad the boat was on the the trailer, and not a few miles offshore with you and family on board! I've got a 4-person aviation life raft that does double duty in the boat when I'm not flying - for exactly this reason.

- Clay

mastreb wrote:If you don't have the terminal post covers, you can use "Sugru" (from Sugru.com) to form a cap over them. You can even buy it in red and black. It's waterproof silicon rubber that forms a hard part after 24h of exposure. Check out their website, it's super useful stuff.

Amazon carries the stuff. Very cool. I just bought some. Good to have on board, like Rescue Tape.

Liquid electrical tape would also do the job, and is readily available. I've seen only black, but it might be available in colours too.