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Circuit Breakers vs. Switches

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tomh
1st Mate

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USA
83 Posts

Initially Posted - 07/02/2014 : 12:56:22

I would appreciate your input on whether it is acceptable to use a circuit breaker panel as a switch panel to control DC circuits.

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 07/02/2014 : 17:36:07

I don't like breakers in a marine environment--fuses are more reliable. Breakers can work as switches, but I wouldn't use them instead of fuses. I have switch panels with fuse slots on the backs.

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Voyager
Master Marine Consultant

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USA
5231 Posts

Response Posted - 07/05/2014 : 08:37:26

I agree with David about not substituting breakers for fuses but if you have a suitable panel with 8 or more breakers you could use that as a switch panel. I'd install a line from the battery to the panel through a 30A fuse to a separate MAIN house on/off switch to feed all circuits including the panel. Then I'd wire a + bus bar and a - bus bar. I'd connect each breaker separately to the + bus bar through a 5. 10 or 15A fuse depending on expected loading. Then I'd run each circuit out from the breaker: VHF, navigation lights, bow light, anchor light, deck light, auxiliary - depth, GPS, speed, entertainment and cabin lights. I'd connect each negative return to the - bus bar.
Use appropriate sized wire based on expected max current x 2x the cable run. Don Casey includes a wire gauge table in his books...

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islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 07/05/2014 : 09:39:55

I don't see a problem using breakers as switches. Many boats that I have owned did their panels this way usually on larger boats. For example my friends Island Packet, It's very common. I think our boats use switches just because it was cheaper do do so.

Edited by - islander on 07/05/2014 09:42:45

Lee Panza
Captain

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USA
465 Posts

Response Posted - 07/06/2014 : 08:03:21

My personal preference is for breakers rather than fuses, for several reasons.

First, when a short circuit or an equipment malfunction blows a fuse, it may likely not be immediately evident where the problem is. With a breaker I can attempt to reset it each time I disconnect something from the circuit until I locate the problem and the breaker no longer trips. With fuses I would blow another one each time, so I'd have to have a pile of them available. Of course one could patiently work their way through the system with a continuity tester instead, but when I'm out on the water in the dark and the wind and waves are up I don't have an abundance of patience for equipment malfunctions.

I also don't like having to open up a panel and fumble around near all those exposed electrical contacts when I need to get the power back on quickly. Fuse blocks should be very conveniently accessible and well-labeled, but they often aren't. When the holders are designed for replacing the fuses from the front of the panel they generally have a cover or cap, which immediately doubles the number of parts that can slip out of my fingers. I suspect that I'm not the only one who sometimes has difficulty manipulating small components when I'm cold, wet and tired; I think I'd have to be mentally prepared for the ritual of dropping, finding, cleaning and then trying again to insert, and I'd have to be prepared to do it more than once. Just happens sometimes.

If it's the primary protection at the batteries that blew, inserting a replacement fuse before I've found and corrected the problem could be kind of exciting.

There's also the question, when something goes dead, of whether it's the fuse or the equipment that failed, and pulling and examining a fuse under adverse conditions can be a challenge. Some types of fuses need to be examined very carefully to determine their condition.

And then there's the need to keep a supply of assorted different sizes and to store them such that I could immediately get my hands on the particular replacement that I need.

Yes, once in a great while a breaker goes bad, although the ones made specifically for the marine environment, like those sold by Blue Sea or Paneltronics, are far more reliable than the ones used in a lot of other equipment. I don't think reliability is much of an issue anymore. I have a spare of each size just in case, but I suspect it was money I needn't have spent. By the way, I've had circuits go dead due to bad contact between fuses and the holders. Maybe the first thing one should do when a circuit goes dark is simply pull and reset the fuse.

Both Blue Sea and Paneltronics encourage the use of their breakers as switches, which simplifies the electrical system. The same component that activates my navigation lights tells me immediately if there's a short in one of the light sockets. And the same component that protects the circuit to my bilge pump allows me to easily disconnect the pump when I want to service it.

By the way, when sizing overload protection devices, keep in mind that it's the wiring you're protecting as much as the components on the circuit. The heat from a short circuit can do a lot of damage in the inaccessible spaces that the wiring runs through. As Voyager mentioned, there are tables that can help with designing or upgrading an electrical system.

I'm sure there are good arguments in favor of fuses. On disadvantage of using breakers for switching individual circuits is that it generally rules out having integral lights like some switches have. I think that might be helpful in the dark. Some panels on the market have built-in lights next to the breakers, but if you're building a panel as a DIY project that's an added expense and complication. On the other hand, with any light at all it's easy to see the position of a breaker/switch.

Having said all of this, I'd have to concede that for a lot of people it doesn't matter which they use for overload protection. I'd be willing to bet that many boatowners have never had a fuse blow or a breaker trip. Electrical overload protection is like insurance; it's something you may never use, although it's important to have just in case. But sometimes the choice between fuses and circuit breakers just comes down to personal preference. In my case, I'm setting up my boat for extended cruising when I retire in a few years, and for me the ability to troubleshoot and repair problems under difficult conditions is an important consideration. In my opinion, that old philosopher Murphy was something of an optimist: not only will things go wrong, they'll go wrong at the worst possible time.

So, that's my two-cent's worth, and probably worth every penny you paid for it.

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 07/06/2014 : 13:48:45

OK, then I'll suggest that with breakers on a boat, especially in a salt water environment, about once a month flip through all of the breakers to make sure they operate freely. I might also spray a dry lube/protectant on them.

Most of us have probably never experienced an electrical failure, although I have on another person's boat, resulting in smoke pouring out of the galley and the "dumpster". It was a short across wires that chafed at a screwed-down wire tie and burned about a foot of insulation in the dumpster. The breaker on the circuit never tripped. It's a bad feeling, even if only 10 miles from port on the Pacific.

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Voyager
Master Marine Consultant

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USA
5231 Posts

Response Posted - 07/11/2014 : 07:47:17

Agreed - everything fails sooner or later.
If a breaker fails in an open position - no harm, no foul - replace it.
But if a breaker fails in a closed condition, your electrical circuit in simply NOT protected.
Fuses are cheap, buy a few boxes.
Boats, and sadly lives, are not.
We had two separate instances of boat fires nearby in the past few weeks.
Several boats were a complete loss - thankfully no lives were lost but one boater received severe burns.

Edited by - on

sweetcraft
Admiral

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USA
816 Posts

Response Posted - 07/16/2014 : 22:26:48

It was after Dave's story of sailing out of San Diego that I found and used these breakers installed at the btry in their boxes. RV supply and my own adaptor.

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Akenumber
Navigator

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USA
247 Posts

Response Posted - 07/24/2014 : 18:19:08

After dealing with a lot of marine and off road situations I would like to recommend using a breaker pannel for switches and using a maxi style fuse on main leads. That way you are double protected. At least some what for heavy and lower amp circuits. High amp fuses can usually be switched out for slow blow or quick. Depending on what's on the other end.

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