Help with correct breaker size

[workinprogress]

Thanks for all the help in my previous post. I have a few more questions. I have a bilge pump and livewell pump that both draw 2.1 amps @ 12V. The instructions say to use a 2.5 amp fuse for each. I have 2 recirculation pumps that don't list the draw, but say to use 2 amp fuses. All of these pumps came with 16ga wire. I can get circuit breakers for the panel I purchased in 3,4,5,7, and 10 amp sizes. I used the circuit wizard at Blue Seas and it shows the 5 and 7 amp breakers as optimum. I'm figuring a 5 ft run of wire for each of these pumps. Do I use the size breaker the pumps call for or do I use the Blue Seas reccomendation? I also have a bow light that I have no way of knowing the draw of. It is one of the small, generic ones that can be purchased anywhere. There is a 20ft run of wire from the light to the switch panel. What draw should I assume, and what size breaker will work. I have not purchased my gps yet but want to get the breaker for it when I order these other ones. Anyone know what size breaker to use for a small (probably 4") gps unit? Finally, I have a question about wire size. The circuit wizard reccomends 18ga wire for these items. Is there any drawback to using larger wire than you need for conductivity? I was thinking about using 14ga just because it is stronger. Thanks.

[Shakespeare]

Do I use the size breaker the pumps call for or do I use the Blue Seas reccomendation?

I always defer to the equipment manufacturer's recommendation. BlueSeas seems to be somewhat over conservative on some of their recommendations for wire and breaker size. Nothing wrong with that but in some cases it's a bit of overkill. If you install the wiring in accordance to the manufacturer's specifications then if anything should go wrong with the equipment you can state it was installed according to their instructions.


I also have a bow light that I have no way of knowing the draw of. It is one of the small, generic ones that can be purchased anywhere. There is a 20ft run of wire from the light to the switch panel. What draw should I assume, and what size breaker will work.

Like the lighting in your house, you can size a generic circuit to protect multiple lights. You're not really protecting the lights per se' but protecting the circuit that feeds them. A 5 or 10 or 15 amp circuit should be more than sufficient to take care of bow, anchor, and misc. lights. If you can get the wattage rating of your light bulbs then Amps = Watts / Volts. My bow light is 10 watts (.83 amps)


I have not purchased my gps yet but want to get the breaker for it when I order these other ones. Anyone know what size breaker to use for a small (probably 4") gps unit?

GPS, VHF radios, and other misc. electronics usually have an inline fuse that takes care of their needs. You can size one generic circuit to take care of all the electronics as long as you still employ the inline fuse. If you do away with the inline fuse then you need to refer to each device's specifications to get the correct ratings. My Garmin 440S uses a 3 amp fuse and the Uniden Oceanus uses a 6 amp fuse. This doesn't mean that is how much current they draw, but what is suggested for overcurrent protection. I would probably use a 10 or 15 amp generic circuit for my equipment and still employ the inline fuses.


Is there any drawback to using larger wire than you need for conductivity? I was thinking about using 14ga just because it is stronger.

There is nothing wrong with upsizing the wire a size or two above the suggested minimum rating. If anything, you're helping the situation because there is a voltage drop in DC circuits with longer wire runs.

Mike C.

[workinprogress]

Thanks Mike. You have just about done everything but crimp my connectors on for me.

[Shakespeare]

Thanks Mike. You have just about done everything but crimp my connectors on for me.


I'd do that too, but I work for beer and you probably can't afford me. LOL

Hey, I just made a slight update to my post. I went out and looked at the wattage of my bow light and made note of it... so read that section again.

Mike C.

[NOTHING ELSE MATTERS]

I was going to answer your questions, but this guy(Mike C) left nothing out, so good luck and let me know how much beer you gave him. ;D

[workinprogress]

One more question. For the equipment listed, what size main inline fuse should I use?

[NOTHING ELSE MATTERS]

What are you try to do? Pull a main line and then branch off? If yes, what size wire did you pull?

[workinprogress]

This is for a j16. I have a battery under the front deck for the trolling motor. I am planning to use a single battery for the motor, bow light, livewell pump,2 recirculation pumps,bilge, and gps. I am going to run two cables from the + side of the battery, one to the engine without an inline fuse, and one to a bus bar. From the bus bar the individual wires go to the combination breaker/switch panel and then on to the components. The negs will be collected on a separate bus bar. If you see any flaws in this setup let me know. I am new to this. Thanks.

[Shakespeare]

Well... let's see;

Bilge pump 2.1 amps
Livewell 2.1 amps
Circ. Pump #1 1.5 amps
Circ. Pump #2 1.5 amps
Misc. Lighting 3.0 amps
GPS 2.25 amps

Total = 12.45 amps

X 125% Safety Factor = 15.57 Amps

Your main fuse protects the feeder going to the breaker panel and/or buss bar. In general, the feeder wire is sized to accomodate the total capacity of the breaker panel and/or buss bar. If you purchased a 60 amp panel then you would probably want to use #10 or #8 gauge wire (105 deg. C) and fuse it for 60 amps or more for loads distributed off the buss bar. Even though you're not going to be using 60 amps or whatever, you're providing for future growth. It is your option if you want to use a fuse rated at a lesser value. In your case a minimum of a 20 amp fuse would be required to accomodate your existing load. If you do this however, you have provided no room for growth and will have to "fuse up" in the future to accomodate any additional equipment that is to be added.

You should not size the main fuse greater than the ampacity of the feeder wire and/or the maximum capacity of your breaker panel and/or buss bar.

See the chart; http://bluesea.com/viewresource/529

Mike C.

[NOTHING ELSE MATTERS]

A 30 amp fuse for main should be enough, but i don't like the idea running a hot wire from battery to engine without fuse.The size of the fuse is always according to the size of wire used .Length of wire in your case is not critical.
From the buss bar connect your electonics with THEIR supplied fuse, do not change/upgrade fuses,speciially on the GPS.
Hope that helps, i hope i understood your question correctly.

[workinprogress]

I thought I read somewhere a fuse in the line to the motor was unnecessary. I can put one in easily enough. I have a 25hp 2 stroke Yamaha. Should I use a fuse, and if so what size. The pumps and light don't have supplied fuses. I am planning on using this panel with 3 amp circuit breakers.http://bluesea.com/category/7/27/products/4386 Can I run the gps through here and still use it's supplied in-line fuse after the panel? It's unnecessary double protection, but it will keep all my wiring going through the same place. Thanks.

[Shakespeare]

There is usually an in-line fuse on most motors inside a small rubber fuse holder. It is an extremely short fuse holder with a short 20 amp fuse in it. It's usually located near the solenoid on one of the red wires. If that fuse is blown you will get nothing at the switch.

I don't believe the starter wire itself is fused because it is an intermittant high inrush load. Someone correct me on that if I'm wrong.

Mike C.

[Shakespeare]

From the Blue Sea technical brief on circuit protection;


Notice that wires intended to carry engine-starting currents between the batteries, the switch, and the starter, are not required to have main-circuit-protection devices installed.

This exception is based on the notion that the starting battery would have just enough power to handle starting the engine, and the wiring would be appropriately sized such that the full capacity of the battery would be unlikely to overstress the wire. It was also assumed that the batteries would be very close to the engine.



http://bluesea.com/viewresource/98

[NOTHING ELSE MATTERS]

I don't believe the starter wire itself is fused because it is an intermittant high inrush load. Someone correct me on that if I'm wrong.

Mike C.



I'm almost positive that it is fused, actually is a breaker close to the engine.

[Shakespeare]

The pumps and light don't have supplied fuses. I am planning on using this panel with 3 amp circuit breakers.http://bluesea.com/category/7/27/products/4386 Can I run the gps through here and still use it's supplied in-line fuse after the panel? It's unnecessary double protection, but it will keep all my wiring going through the same place. Thanks.


Here's what I would do if it were my electrical system;


Run a feeder from the battery to the circuit breaker panel
Install a main fuse at the battery that protects the feeder
Provide circuit breakers for each of the pumps
Provide a 15 or 20 amp circuit breaker that feeds the positive buss bar
Connect electronics and any other devices that have inline fuses to the buss bar
Provide a utility breaker for lighting


I think you mentioned tagging your feeder to the bussbar then hopping over to the circuit breaker panel. That's ok as long as you make absolutely sure that any branch circuits that comes off that bussbar has overcurrent protection within close proximity.

In all cases the branch circuit wire should be of suitable size to carry the load and have the appropriate overcurrent protection.

Your question about double coverage... you can do that if you want but it will be two places you have to examine if there's a problem.

Mike C.