Breaker Talk

[Dave_E]

Hi All,

The good ship came with a beautiful 15 switch DC panel, LEDs, very nice. Top 2 rows are all 20A breakers, the bottom row (5 each) is 15A.

The way I've always understood these type of panels with switches was to power things like water pumps, ships lights, things that actually get actuated from this switch without having to install in-line fuses everywhere.

Th PO's have about half the panel doing this and the other half is just providing power to devices that have their own on/off switches and then most of them are in-line fused as well.

I view that as a waste of switch breaker. In a perfect worls should devices that have their own on/off be wired to a power distribution junction, which is fed by battery power via the big bat select switch?

Dave

 

[aboatman]

There's no way to answer your question without a lot more detail.

Normally, there wouldn't be a circuit breaker and a fuse in the same circuit but if the wire size changes to a smaller capacity, either the circuit breaker should be changed to match the smaller size or a fuse should be installed where the wire size changes. For example, a 20 amp circuit feeding a plotter which comes with its own power cable.

Circuit breakers are not normally intended to be used as switches although they can be used to shut off the power. A refrigerator that is normally left on would be turned off by the circuit breaker. Lighting circuits would have a circuit breaker but normally have individual switches so you don't have to go to the breaker panel to turn them on and off.

 

[Xsbank]

The breakers are there to protect the wire to the device. The device should also be protected. Many devices on boats do not have that protection, for example, your vacuum in your house will probably have a breaker right on it and you know the distribution panel has a breaker.

I have a breaker switch for "hydraulics" that energizes a solenoid, there is no other switch. I also have a breaker for "forward cabin lights" which has numerous switches. Neither of these circuits have fuses at the device although technically they should, to protect the device.

Breakers can absorb significantly more current before they "break" than a fuse (generally speaking) and so you can significantly overload a breaker and it won't pop unless there is a short, which is what they were designed to protect against. The device at the end of the line could overheat and be lost or damaged before the breaker popped to protect the line but without a fuse on the device it could catch fire or have a similar catastrophic failure and the breaker might not break.

 

[DavidM]

Here is another take on your question:

Marine devices generally come in two catagories: 1)Those that are used intermittently and are not critical to the boat's operation or safety and 2) Those that should never or rarely be turned off as they are critical.

Panel breakers or fused circuits with on/off switches are used for #1. I like the way Mainship wires the #2 catagories. It has a separate panel in the engine room (Pilot 34) or near the battery switches (34T) that has breakers but they are not easy to turn off. It takes a small screw driver to turn them off. This panel serves things like bilge pumps and fire, CO and smoke detectors.

Older boats use multiple fused circuits wired directly to the battery terminals for #2. This works but is not ideal since when a fuse blows you have to find a replacement. Circuit breakers can easily be reset and as discussed above don't blow immediately.

Whether your #1 devices have a dedicated circuit breaker or multiple devices on one breaker or multiple devices on one breaker but each protected by individual fuses is a matter of choice, but here are some guidelines:

I would user on device per breaker for larger loads and loads that you don't want tripped off due to a failure in another device.The macerator pump would be one of former, the navigation system one of the latter.

Fans and reading lights are examples of devices that can be ganged on one breaker and in most cases don't need to be protected by individual fuses as long as you use large enough wire.

David

 

[dingy]

Helping a friend install a macerator and it requires a 25 Amp breaker.
We removed a 10 Amp that wasn't being used and it was a Klixon, 60Volt, 10Amp. It has a model number 4MC6-1-10 BOA (the -10 is for the amperage I'm pretty sure)
Where could I get a Klixon 60Volt, 25 Amp breaker that would fit where the 10 amp was removed? Also, the new macerator came with a fuse. If we use the breaker would there be any need for the fuse? thanks for any advice,

 

[sawdustdad]

Not very familiar with Klixon breakers, but this site has lots of them:
https://www.peerlesselectronics.com

That part number doesn't show up, though.

As far as fuse/breaker, I always remove the fuse when powering with a dedicated breaker, just make sure the wiring is sized for the breaker. A 25 amp breaker needs a 10 ga wire in most applications.

 

[Xsbank]

I will repeat myself for emphasis: the breaker protects the wires and should be sized for the size of the wire. You then need to protect the device, usually with a fuse. Small devices like lights can be “ganged” together with bus bars or similar on one fuse. A pump should be fused to protect the device. The macerate fuse shoul be retained!

Almost every answer to an electrical question can be answered by Nigel Calder’s book. Every boat owner should have one in their library and you will live your life in bliss and enlightenment.

 

[psneeld]

As long as the wire going to the device is rated ampacity wise above the fuse that protects the device, and the CB is rated as the same as the fuse provided with the device... The in line fuse can be eliminated. If worried about damage to electronic devices on a CB instead of a fuse, see the last paragraph.

My setup is to use fuse blocks throughout the boat where short runs to multiple devices what are switched themselves or don't need to be...and each fuse block has a CB on the main panel.

A classic setup is to get all the hard to find in line fuses in electronics by installing a fuse block with the same fuse ratings in an accessible place near each helm station.

 

[diver dave]

I will repeat myself for emphasis: the breaker protects the wires and should be sized for the size of the wire. You then need to protect the device, usually with a fuse.

This is especially true with electronics. You will see depthfinders, MFD's, VHF's, etc with some odd in-line fuse sizes. Part of the mission is to protect the electronics from reverse polarity connection issues. If the engineer did it right, the fuse will blow before the protection diode and other, more $ items within. And, there is more than just the breaker/fuse Amp rating; the time delay curve may come into play also.

 

[sawdustdad]

This is especially true with electronics. You will see depthfinders, MFD's, VHF's, etc with some odd in-line fuse sizes. Part of the mission is to protect the electronics from reverse polarity connection issues. If the engineer did it right, the fuse will blow before the protection diode and other, more $ items within. And, there is more than just the breaker/fuse Amp rating; the time delay curve may come into play also.

I suspect that electronics manufacturers include in-line fuses because the typical boater installs more than one device on a single switched/fused circuit. Hence the need for individual circuit protection. In addition, most electronics come with smaller gauge wires that have limited ampacity and require suitable fuses.

If you wire each device individually to a dedicated fuse block and size the fuse for that device the same as the mfg, then you are not negating the mfg intent. You'll also have easy access to the fuses, and won't be hunting through a mass of wiring to find that in line fuse somewhere. In-line fuse holders are problematic as well. Don't like most of them.

I set up a pair of Blue Seas 12-place fuse blocks, each powered by a 30A breaker. Removed all inline fuses and switched each piece of electronics separately, with fuses in the fuse block corresponding to those of the mfg.
All fuses easily accessible, and replaceable with minimal effort.

Not exactly germane to this discussion, but each fuse block is powered from a different battery, and the electronics are split between the two so there is some redundancy. In addition, they can be cross-tied in the event of a failure.

I have two additional 30A breakers supplying the helm with power through a panel of about 20 thermal breakers for helm devices which are then individually switched--wipers, horn, nav lights, panel lights, blower, etc.