to fuse or not to fuse

[capn_billl]

Like Skipmac said.

I bought a handful of inline rubber bus fuse holders.

And I keep a box of various fuse sizes.

Everything gets a fuse.

I coat the holder in noalox before installing.

Fuses are put in obvious places so I will see them when I go to find out why something stopped working.

[waynetmazan]

There is only one question.. Is there a disadvantage to putting a fuse in ???

[LooseGoose]

YouTube University has a great wealth of resources, including videos by Pacific Yacht Services, authored by a credentialed electrical engineer.

https://youtu.be/VwK6rCaEVL8

demonstrates well the importance of protecting circuits, including live fires!

[theBigKahuna]

this fall we had a minor electrical fire. The knucklehead for the previous owner who wired up the WIFI booster / router put a fuse on the router (all electronics internal to vessel), but did NOT put one one the POE Injector on the booster.

I noticed a kink on the injector wiring (mentioning it to my wife) and while reconnecting the router that kink crossed the wires and started burning (kinda like that opening sequence on the old Mission Impossible) until we shut off the battery bank.

Maybe I'm being anal, but I'll be using a fuse here and on some Genset wiring I have to do... IMHO (I'm also NOT an electrician so take w/ grain of salt).

Cheers,

jBrad
s/v Fuzzy Logic

[Ninedotsix]

I think I understand from all that protecting the wire from overheating is the goal, so fire can be prevented.
That's long been my understanding.
It's also known that fuses blow faster than breakers trip, when that makes a difference.
The thing I'd like to have in this discussion is the ABYC guidance, and although $130.00 for a copy of ABYC/ANSI E-11 2018 AC and DC Electrical Systems on Boats is a small price to pay for good advice from the source, it should be offered free as a basic safety resource.
Please let me know when ABYC/ANSI has come around to a higher calling.
There are some fragments of the standard available on the web, and I encourage anyone who is doing boat wiring to exhaust the available knowledge base to do their wiring projects safely.
My $0.02
9.6

[Lake-Effect]

Originally Posted by Ninedotsix

The thing I'd like to have in this discussion is the ABYC guidance, and although $130.00 for a copy of ABYC/ANSI E-11 2018 AC and DC Electrical Systems on Boats is a small price to pay for good advice from the source, it should be offered free as a basic safety resource.
Please let me know when ABYC/ANSI has come around to a higher calling.

That day will be approximately when ABYC becomes wholly funded by US tax dollars, instead of a non-profit funded by memberships, spec sales, education, and related services. Write to your member of Congress now.

In the meantime, yes there are tons of references online already, and any decent book on boat electrical systems (most of which are well under US$130) contains enough info from ABYC to keep the user on the safe path.

btw, the ABYC guidance is that protective devices are selected to protect the wire, and the protection device must be within 7" of the voltage source (battery or higher-gauge distribution point). I don't believe that ABYC has any official pronouncement on fusing to protect individual devices. The device manufacturer should specify a fuse if it's required.

[john manning]

YES YOU NEED A FUSE.

To those who say a fuse is an additional failure point, when a fuse blows it is not a failure, it is a device working successfully and doing the job for which it was installed.

[Wireless1]

Originally Posted by skipmac

Another issue, most bilge pumps and indeed almost all electrical and electronic stuff I have on board has relatively small wires built into the device, wires that cannot be changed and small enough that a 15 amp breaker isn't going to protect that section of wire.

A common rule; The fuse protects the device (faster), the breaker protects the wiring.

[calmissile]

Being an electrical engineer, there is no topic that gets me more heated than this one. I recently purchased a sailboat that has a terrible electrical system installed. When I started to rewire everything, I began with the installation manual for each piece of electronics (mostly Raymarine).

It seems that every component comes with a pigtail fuseholder that you are supposed to splice. Initially, none of the navigation or radar worked. In taking things apart I discovered inline fuses all over the boat. I eventually found a wiring error (shorted + to -) on a terminal board and corrected the problem.

After fixing this problem and getting most of the systems working I began thinking about what would happen in nasty weather if suddenly something critical stopped working. As it was, I would have to pull up floorboards, look in cabinets, etc. in order to track down the blown in-line fuse. How utterly stupid a design that hides in line fuses all over the boat. Do you really want to be crawling over the boat looking for a fuse holder in bad weather? Me neither!

The automotive and aircraft industries solved this issue many years ago. The aircraft industry generally has breaker and switch panels located in one place that the crew can easily access all of them. No remote locations in the wings, etc. The reasons for this is obvious.

Same thing in all our automobiles. Not only is it smart from an electrical design standpoint, it is also faster and easier for maintenance. That is why we have fuse blocks. They are relatively inexpensive and you can afford to fuse individual items rather than tying a lot of them together and loosing all of them when only one causes the fuse to blow.

Using the factory supplied in-line fuses at the device is stupid. They also do not protect the wiring between the fuse holder and the power source.

A good example of this is in my pedestal nav pod that has the chart plotter and other instruments. There are two inline fuse holders inside the pod per the installation instructions. If a fuse were to blow while under sail, the first problem would be finding the correct 'tamper proof' wrench to get the nav pod apart and gain access to the fuses. I would be willing to bet that the majority of sailors do not even have the special wrench to take the nav pod apart.

When I get done with the retrofit, all the fuses and breakers will be at the nav station and will liberally use fuse blocks at that location. Enough said!

[CharlieJ]

@wireless1 #38
That may be a common rule in your industry but it is certainly not a rule in the marine industry.

[Frankly]

Originally Posted by calmissile

Using the factory supplied in-line fuses at the device is stupid. They also do not protect the wiring between the fuse holder and the power source.
Enough said!

A fuse/breaker will protect a circuit against overload when located anywhere along the circuit path. It will not protect the circuit against short circuits or ground faults between the fuse and the source.

With a few exceptions if the fuse blows (good weather or bad) replacing it is likely to bring a very short resurrection of the function (assuming it was properly sized in the beginning).


Frankly

I do have the special Allen wrench handy, but I don't have any fuses in my Navpod.

[calmissile]

Originally Posted by Frankly

A fuse/breaker will protect a circuit against overload when located anywhere along the circuit path. It will not protect the circuit against short circuits or ground faults between the fuse and the source.

With a few exceptions if the fuse blows (good weather or bad) replacing it is likely to bring a very short resurrection of the function (assuming it was properly sized in the beginning).


Frankly

I do have the special Allen wrench handy, but I don't have any fuses in my Navpod.

Agree with both of your comments.

Since there are a lot of DIY boaters out there doing their own wiring I have a few recommendations to pass along with the reasoning behind them.

Having your fuses and breakers located in one place allows you to go directly to them and locate the open fuse. No lost time spent having to open up panels and hatches, etc.

There is nothing wrong with using sub-panels in other locations of the boat when it is necessary to minimize the voltage drop over longer distances. Still, use fuse blocks to separate the various loads at the sub-panels.

To the extent practical, do not connect many loads onto one fuse. Think about what will happen when the fuse blows. Do you want to lose all cabin lights or would you be better off dividing the loads in half and at least have some lighting still working if a fuse blows.

Do you want to lose all of your navigation equipment when one fuse blows or are you better off to have fused them separately? What about navigation lights? Wouldn't it be a good idea to have the mast lights on different fuses from the deck mounted lights?

Of course there are tradeoff's. When adding a new piece of equipment there is a tendency to just tack on to the nearest power circuit. It may not be practical to fuse every component with individual fuses. Running more circuits means more wire to run and the labor to run it. Nevertheless, it is often the best solution but not the cheapest one. Keep in mind that you only need to size the wire based upon the loads that are attached to it. In many cases it is smaller wire than what is necessary for having a bunch of loads tied to one circuit.

Your comment about a short restoration of function after replacing the fuse is worth expanding on. There generally are two reasons a fuse blows. First is because the instrument or equipment has developed a short or overload condition that is permanent. Changing the fuse will simply blow another fuse. The other case is a transient condition where the unit experienced a temporary overload (like from a voltage spike) and will continue to function when power is reapplied. In this case the unit will operate after the fuse is replaced. My personal protocol is to replace the fuse once and see if the problem is corrected. If the second fuse blows, then its time to separate any loads on that circuit and determine which one is the cause.

I recommend every boater with electrical systems to have a basic VOM (Volt-Ohm-Meter) or DVM (Digital Voltmeter) kept on the boat. They are very inexpensive (around $15) and they are invaluable in troubleshooting simple 12 VDC circuits. Just make sure to never leave them in the Ohms or Amps functions when you put them away. Otherwise you might be spending another $15 when you connect them to a voltage source next time you use it.

The automotive blade type fuses and fuse blocks are inexpensive enough to properly design and implement good fusing practices.

When doing wiring modifications its a good idea to think through what is on each circuit and what systems will go down when each fuse blows. Personally, I like to fuse equipment individually, but like everyone else, we sometimes need to combine loads of the same type on a circuit. If only marine wire were less expensive.

[DeValency]

Originally Posted by shadowdancer

just put in a salt water wash down pump and attached to my 15 amp panel. Do i need a fuse in between the panel and the pump ?

Any device connected to your panel should have a breaker. You don’t want to piggy back on other breakers if possible. A breaker (or fuse, if you really like this) is a cheap expense considering the potential damage due to shortcuts in the circuit or pump.