~Circuit Breaker Sizes, Correct placement of Breakers Help~~

[cturboaddict]

Okay, as time is getting nearer for better weather- Im looking at picking up a few more items to start my rewire. Id like a few suggestions on what sizes of a few items, as I dont want to start a fire.

Here are the load items~
1. CMC PT130 tilt/trim (operates on two 40amp relays)
2. Ignition
3. Bilge
4. Horn
5. Radio (nothing fancy, just a radio and some speakers at the moment)
6. Dash Lights/Running Lights
7. Anchor Lights
8. Gauges
9. Interior Lighting
10. Cigarette Lighter (for charging cellphones and what not)

Im looking at running a dual battery setup, with a Battery Selector switch.
Im probably looking at 4gauge wire for the batterys to the selector (also where the tilt/trim will plug in, and then 6or8 ga from there to the fuse panel. 14 ga after that.

Question is- What size breaker should i use after the selector switch towards the fuel panel? Or do I need two? (one for each battery? If so, What size? Also, Im going to run a resetable breaker inline for the 2 40amp relays, is 50amp safe there?

What is the best place to tap into a switchable source for the gauges? (Its a 76 Mercury 115 TOP)

Anything missing here that Ive got jotted down? Help me make sure Im on the right track.....

 

[MH Hawker]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

their actually at least 2 independent electoral systems on a boat, one is for the motor and related items and that often includes the gages. The second is the console and from that you have the lights fish finder, stereo and other assorted gadgets


system one
the motor system all ready should have its own fusing installed often under the motor cover not sure a bout the trim relays I have never messed with I am sure some one who has will chime in.

1. CMC PT130 tilt/trim (operates on two 40amp relays)
2. Ignition
8. Gauges


system two

This runs ever thing else and unless thier is a item over 10 amps it is simpler to run all or these wires out of 16 ga wire from the fuse or breaker panel although you may find the cost of breakers a but high thier around 30.00 each verse .50 cents per fuse. The main power feed to the fuse or breaker panel from the battery should be at lease 30 % larger than the wire size of the expected total load and be fused at the battery's This is for future needs. Any device over 10 amps should be wired according to its amp load.



3. Bilge
4. Horn
5. Radio (nothing fancy, just a radio and some speakers at the moment)
6. Dash Lights/Running Lights
7. Anchor Lights
9. Interior Lighting
10. Cigarette Lighter (for charging cellphones and what not)


Now all of that being said, fuses do not protect devices. Fuses protect the wiring, their use is to stop the wires from melting from a over current load or short circuit and catching things on fire. Below is a wire and fuse chart. I hope that helps you out.

12 v amp per wire gage

in runs or 25 feet or less
20 ga 2.5 amps
18 ga 5 amps
16 ga 10 amps
14 ga 15 amps
12 ga 20 amps
10 ga 30 amps
8 ga 50 amps
6 ga 75 amps
4 ga 100 amps
2 ga 200 amps

 

[Silvertip]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

More clarification.

1) You do not switch the gauges. They get their power via the "A" terminal on the ignition switch. No other switching or fusing is necessary.
2) If you are using a dual battery switch, everything on the boat except for an automatic bilge pump would be connected to the COM terminal on the switch. Automatic bilge pumps connect directly to the house battery.
3) 14 gauge wire is too heavy for most accessories and ot of the question for wiring gauges due to the bend radius and tight quarters. It is simply not necessary for anything drawing under 10 amps.
4) That is not a cigarette lighter socket. It is an "accessory socket". They are very different. Check the maximum current rating for the device and wire it accordingy.
5) You install a 30 amp breaker at the COM terminal on the switch. That breaker feeds 8 gauge wire to a fuse panel. You run an 8 gauge wire from the ground buss on the fuse panel back to the NEG terminal of the battery.
6) All accessories are wired to the applicable switch and the switch receives power from the fuse panel using an appropriate fuse. If the device has it's own switch you wire directly to the fuse panel.
7) Dash and running lights as you call them are two separate circuits. Instrument lights are wired from the NAV side of the NAV/ANC switch. That is a special ON-OFF-ON switch so you can select BOTH the bow and stern lights or just the stern light when anchored.

Here is how this stuff is generally wired: Below is a wiring diagram for a simple single circuit (a courtesy light in this case).

Here is a typical boat-side diagram. Engine diagrams are in the engine service manual.

 

[cturboaddict]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

First off.... THANKS FOR ALL THE INPUT SO FAR. Its starting to clear up alot of questions.

Okay~
With what you guys have informed me, my question only lies here now....
1) I have the wired controls that have battery connectors on them. With my configuration, I should wire that directly to the COM terminal on the selector, NOT TO THE BATTERY. It should be fused internally already somewhere in the motor... Correct?
2) On the same COM terminal, I should run a 30 amp breaker inline to the fuse panel w/ 8gauge wire, Correct?
3) The PT130 can also be hooked directly to the COM terminal and have a breaker installed inline, What size? (Reason I ask, is the old relays/wiring that came with the PT130 are shot, and for $10 a pop i can get new wired relays)

 

[Silvertip]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

First off.... THANKS FOR ALL THE INPUT SO FAR. Its starting to clear up alot of questions.

Okay~
With what you guys have informed me, my question only lies here now....
1) I have the wired controls that have battery connectors on them. With my configuration, I should wire that directly to the COM terminal on the selector, NOT TO THE BATTERY. It should be fused internally already somewhere in the motor... Correct?

I have no idea what you are trying to explain. What wired controls?

2) On the same COM terminal, I should run a 30 amp breaker inline to the fuse panel w/ 8gauge wire, Correct?

Yes -- 8 gauge wire is fine as is a 30 or 40 amp breaker. You don't have anywhere near that kind of current draw.

3) The PT130 can also be hooked directly to the COM terminal and have a breaker installed inline, What size? (Reason I ask, is the old relays/wiring that came with the PT130 are shot, and for $10 a pop i can get new wired relays)

Whatever size the old circuit breaker was is what you need.
If you want to be able to run the PT130 with the boat on a lift or on a trailer it won't work if the battery switch is set to OFF which you likely would do after the boat is loaded. So that depends on how you want that to work. Remember -- when the battery switch is set to OFF everything wired to the COM terminal will be OFF as well. That's why you were told to wire an automatic bilge pump directly to the battery. It wouldn't run if connected to the COM terminal when the switch is off. Therefore if it rained and filled the boat the pump would be of zero value.

I hope you are creating a diagram because if you aren't you will likely end up with bigger mess and more problems than you started with.

 

[cturboaddict]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

Yes sir, I am. Actually, once completed- it will end up a .dwg file as Im a CAD Drafter. I will share when its done!

 

[cturboaddict]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

As for the "wired control", I was speaking of the controls for the motor... Shifter box if that explains it better. IT has the main harness running off of it directly to the motor.

 

[Silvertip]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

You say the "wired controls" (the control box) has the battery connections on them. No they don't! Battery connections for the engine harness are the big cables that run between the battery and the engine. If you add a battery switch, the ground cable from the engine remains where it is. The POSITIVE battery cable gets connnected to the COM terminal on the dual battery switch. This diagram has been posted a gazillion times here and there are an equal number of descriptions about how to add a dual battery switch but here it is again.

 

[cturboaddict]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

Yes sir, you are correct. I guess I was getting confused as they whole harness runs from the control box to the motor, and that is where the main battery connections feed off of. (EVEN THOUGH, they only wire into the motor)

And you answered my question~ Thanks again!!! You guys rock!

 

[Silvertip]

Re: ~Circuit Breaker Sizes, Correct placement of Breakers Help~~

Yes sir, you are correct. I guess I was getting confused as they whole harness runs from the control box to the motor, and that is where the main battery connections feed off of. (EVEN THOUGH, they only wire into the motor) !

+12 volts and ground also travel up the harness to the "B" terminal (battery) on the ignition switch and ground is provided at the control box as well as the pigtailed part of the harness for connection of the instrument grounds. The "A" terminal (accessory) on the ignitiion switch feeds +12 volts to the instruments. The large battery cables are that large because of the current draw of the starter. From that point on up the harness current draw is much less but nevertheless, that is all one complete circuit from the battery to the igntion switch. If it had 10 junction points along the way, it is still all the same circuit.