Circuit breakers and fuses

[Lake-Effect]

Originally Posted by Frankly

Looks like you suffer from the same affliction as flightlead.

Doodle it out and get back to us.

[flightlead404]

Originally Posted by Frankly

Don't think you understand the differences between the basic electrical terms: overcurrent, short circuit, and ground fault.


Frankly

Ofc I do. I'm an electronics hobbiest and have design, built, and fly behind numerous ground up electrical/electronics installations my aircraft.

[Scorpius]

Originally Posted by Time2Go

Scorplus,
Definitely a belt and suspenders approach
Yes, There is another fuse block coming off the unswitched distribution
bus bars Before the house switch for Bilge, VHF and so on.
Don't know how to keep things on if all batteries are dead??

PS: What a great forum we have
I'm always learning here

Yes, if all batteries are dead, you are "dead in the water" - but that is a far less likely scenario than having one battery fail - and you just hope it's not the one with your master-switch-off critical circuits attached. That's why I have large diodes (110 amp alternator size) from each of the two house batteries to a separate terminal strip to drive those circuits and a thermal automatically-resetting breaker on the bilge pump.

The most likely scenario in my mind is that it is the house battery in use at the time that is most likely to die - and the other one will be fine. With my set-up it doesn't matter which I am using at the time, if it fails the other will keep the critical circuits powered up.

I've also contemplated putting a diode from one of the start batteries (I have two for my single engine - belt and suspenders!) to that system but I'm not sure it is a good idea. I'd hate to lose even one of the start batteries in the event of some unforeseen fault.

Yes, it is a superb forum. I love it!

[Scorpius]

Originally Posted by billgewater

The difference between house wiring and control systems is that boats are much more complicated. It is because of this complexity, that really good planning and the ability to repair or change circuits becomes more important. A house may have 4 or 5 circuits but a boat may have 20 or more. Labels and indicator lights are much more important. The ability to easily change protection levels (i.e. fuses) is also much more important.

"A house may have 4 or 5 circuits . . . "?

My goodness, where do you live? Around here any house built or rewired in the last 30 years or so has at least 20 circuits (in a 24 circuit panel) and more recent builds have closer to 40. The kitchen alone can have a dozen or more circuits - every outlet and every built-in appliance having to have its own.

Personally I think the big differences between boat and house wiring (I've done a lot of both) is that house wiring is much more prescribed by regulation (and inspected for conformance), there's a lot more room to work and run wires and, particularly for us here on this forum, there's much less DIY. But house wiring can be at least as complicated as boat wiring: Have you ever wired a four-way circuit (more than two switches for a single, or single string, of light fixtures)? And some of the low-voltage wiring for security and in-home entertainment systems will drive you crazy! In-floor electric heating systems are also fun. Or the control systems for central, but zoned HVAC systems. All great fun.

[CarlF]

In the high vibration environment of a boat, it's much more common to have a wire short from the insulation chafing than for a device to short internally.

That's why it's important when wiring a boat to start from the battery and install an appropriately sized fuse or breaker every time the wire gauge steps down in size.

It's also a good idea to install a short piece of hose or other chafe protection wherever wires cross a sharp edge or piece of metal such as an engine mount.

[flightlead404]

Originally Posted by CarlF

In the high vibration environment of a boat, it's much more common to have a wire short from the insulation chafing than for a device to short internally.

That's why it's important when wiring a boat to start from the battery and install an appropriately sized fuse or breaker every time the wire gauge steps down in size.

It's also a good idea to install a short piece of hose or other chafe protection wherever wires cross a sharp edge or piece of metal such as an engine mount.

I like to use "snake skin" for this. i.e. expandable wall sleeving. Available from all of your standard electronics supply houses. I like the fiberglass heat/fire/oil resistant stuff. Terminate it with a piece of double wall adhesive lined shrink tube. Works very well and a nice professional finish also.

The only issue, think out your wire runs first, once its in place added an extra run is a pita. In the past I've put in a couple extra unterminated extra lines although I suppose you could put in a pull string.

[Nibiruwayne]

Lots of good answers and info. I like the breaker at a central location and labeled for each circuit- safety when working on a device/ appliance, battery consumption control, and limiting guest usage.

[andrewvik]

I just re-wired my 1976 Islander 36. Where possible I sized the circuit breakers to the appliances they serve. No need for additional fusing downstream.

Even with various pumps and the fridge, I don't think I have any appliance that draws more than 5 amps. Our electronics, nav lights, and cabin lights usually draw less than 1.

Watch Pacific Yacht Systems' amazing seminars on Youtube.

[David B]

Originally Posted by catsketcher

Gday everyone

Apologies if this has been done to death but I want to rebuild my electrical system that looks like a rat's nest. All the wire is nice tinned copper but the setup is pretty awful looking. I want to replace the switchboard and redo the fusing and bus bars.

My question is about setting the whole thing up. I would like a positive and negative bus bar. I am interested in why we have circuit breakers when we sometimes need very low load fuses to protect things like radios. I get that circuit breakers are there to protect the wire and fuses to protect the appliance but why do I need breakers if the fuse is sized lower to protect the appliance?

I don't know why breakers are needed if lower rated fuses are used as well. Am I missing something, I think I am? Fuses are easy to change but breakers are not, so would it not make more sense to have just switches leading to a fuse board with properly sized fuses.

Also if anyone has any links to really nice but simple set ups and how to s that would be great. I have Nigel Calders book but it doesn't really do the design of switchboards.

cheers

Phil

Simple. Circuit breakers protect the wiring in the event of a short circuit or other fault. Fuses, protect the individual components (when installed ...., otherwise it is down to the circuit breaker).

Also - very importantly, the circuit breaker is there to isolate circuits - at the flick of a switch. Very convenient.

On our panel, there is a circuit breaker for each major circuit, then behind the panel on a DIN rail, there are blade fuses feeding off the bus for each circuit to various components, and at the end of the runs, some components have their own internal or in-line fusing as well.

[noelex 77]

Originally Posted by David B

Simple. Circuit breakers protect the wiring in the event of a short circuit or other fault. Fuses, protect the individual components (when installed ...., otherwise it is down to the circuit breaker).

Many boatbuilders adopt this approach to reduce costs. They try to install as few circuit breakers as possible. However, in most instances circuit breakers are also a superior means of protecting individual components.

There are some applications where fuses are superior, but these are rare.

[Time2Go]

Originally Posted by David B

Simple. Circuit breakers protect the wiring in the event of a short circuit or other fault. Fuses, protect the individual components (when installed ...., otherwise it is down to the circuit breaker).

Also - very importantly, the circuit breaker is there to isolate circuits - at the flick of a switch. Very convenient.

On our panel, there is a circuit breaker for each major circuit, then behind the panel on a DIN rail, there are blade fuses feeding off the bus for each circuit to various components, and at the end of the runs, some components have their own internal or in-line fusing as well.

Are DIN rails an an acceptable interconnection
system by the ABYC?
Do they accept ring terminals?
Are they sufficiently vibration proof?
Just wondering?
Cheers
Neil

[noelex 77]

Originally Posted by Time2Go

Are DIN rails an an acceptable interconnection
system by the ABYC?
Do they accept ring terminals?
Are they sufficiently vibration proof?
Just wondering?
Cheers
Neil

The DIN rail is just a mounting and securing system. It is commonly used in industrial systems so there is a diverse range of circuit breakers, terminal blocks, fuse holders etc etc that are available. Some of these options are excellent for marine use, others less so, but there is a wide choice.

Most devices simply clip to the DIN rail so troubleshooting or replacement is easy, which is nice in the tight confines where marine electrical equipment is often installed. The main drawback is the industrial appearance that does not always blend in with the vessel’s interior, but the system is worth considering.

[David B]

Originally Posted by noelex 77

The DIN rail is just a mounting and securing system. It is commonly used in industrial systems so there is a diverse range of circuit breakers, terminal blocks, fuse holders etc etc that are available. Some of these options are excellent for marine use, others less so, but there is a wide choice.

Most devices simply clip to the DIN rail so troubleshooting or replacement is easy, which is nice in the tight confines where marine electrical equipment is often installed. The main drawback is the industrial appearance that does not always blend in with the vessel’s interior, but the system is worth considering.

Yes, on the boats I have seen (and own), the DIN rails are usually behind the panel, holding the additional breakers, sockets for blade breakers and blade fuses, and of course the normal termination blocks - small and large.

I like the DIN system - it is very diverse, versatile and adaptable.