Q about negative connection at distribution panel

[er9]

I'm curious where should negative wires from lights, pumps, electronics etc on the DC side of the distribution panel be connected to ideally?

Are negatives coming from lights, pumps etc...usually connected to a bus bar thats connected to the engine or a bus bar that connects directly to a negative battery terminal?

currently all these negative wires on my boat are connected to the negative post on the back of the voltmeter thats at the panel.

[Wotname]

In general, the negative leads terminate on a busbar that is connected to battery negative.

Larger boats may have more than one negative busbar however they remain connected together and to the battery negative.

Wiring gauge needs to be selected according between busbars.

[smac999]

panel should have a neg bus bar. then a big pos and neg cable goes from panel to batteries. (via battery switch, main panel fuse, and maybe other bus bars at battery)

[coopec43]

Originally Posted by Wotname

In general, the negative leads terminate on a busbar that is connected to battery negative.

Larger boats may have more than one negative busbar however they remain connected together and to the battery negative.

Wiring gauge needs to be selected according between bus bars.

This thread is quite timely.


I have about four negative bus bars all of which will be connected to a four post bus bar located near the battery. (The winch as well as the inverter are also connected to that bus bar)


Now I want to connect the negative bus bar to the bus bars at the instrument/fuse panel. I suppose that needs to be quite heavy as it may need to carry the load of the fridge/freezer, macerator, water maker, radar and galley pump all at the same time? (I think smac999 has answered that)


I have installed a 24V 100A switch for the + winch cable on the instrument/fuse panel. Was that really necessary? (I have also installed a circuit breaker near the winch)


I imagine an autopilot would use a fair bit of power? How should that be wired up: through the instrument panel?



Clive

[Terra Nova]

Originally Posted by coopec43

...(I have also installed a circuit breaker near the winch)...

The circuit breaker must be installed near the power source--not the load.

[er9]

Great thanks for replies.

[billknny]

Originally Posted by coopec43

I have installed a 24V 100A switch for the + winch cable on the instrument/fuse panel. Was that really necessary? (I have also installed a circuit breaker near the winch)

This shows a very basic, and very common, misunderstanding of what a circuit breaker or fuse is for. It is to protect the WIRES not the device.

In your case you have a pari of very large high amperage cables running from the power panel to the winch that are, apparently, unprotected. If through accident, wear, or misadventure, there was to be a short circuit between those wires, they would almost literally explode into flame as the full force of the battery pushed through them. Don't tell me "It can't happen."

If you have never seen the result of a dead short with even a small 12 volt battery, you should. It should be part of every boatbuilders required education. Wires heat in a fraction of a second to temperatures hot enough that molten copper trailing flame sprays every where, while smoke form the vaporized insulation fills the space. It is truly awe-inspiring.

No external fuse or breaker will do anything to protect your winch motor. The motor might (or might not!) have internal thermal protection to prevent an overload, but that is a different matter.

I have seen 3 boat fires, put out two of them and a boat gas explosion. They are frightening events. Most boat fires are either galley or electrical in origin. If you don't know what you are doing, it is far better to leave even deceptively simple DC wiring to people who do.

[jhulmer]

I'm currently rewiring my boat and after many hours of researching CF and other sources, this is what I decided to do.

This is much easier to connect, alter and trouble shoot. It's a work in progress but you can get the idea.

Use the Bluesea terminal strips.

Jim

[P3sailor]

Now, on a slightly different note, are there any boats out there that utilize a "case ground" say for lights, etc. I was on an older wooden boat and it seems to me that all of the originally installed lights were case ground. Any thoughts?

[Cpt Pat]

Ideally, all negative wires should be connected at one "common point" ground, which is then connected to the battery terminal (or series shunt if a power monitor is being used) by a heavy gauge wire.

The purpose of connecting all negative wires at one point is to avoid ground loops: otherwise the voltage drop from a high current load can cause a voltage offset for other loads on the same grounding point. A common ground also reduces noise and interference from being distributed on the negative leads.

Not following this common point grounding rule can be especially vexing when data is being exchanged between devices, because the differences between ground voltages can cause difficult to troubleshoot data errors - this is most critical with "unbalanced" serial data feeds: NMEA 0183 and RS232. Manufactures will often specify connecting the shield on shielded data cables at only one end of the cable run to prevent ground currents from flowing between devices on the cable shield, bypassing interference protection gained by having a common ground point, and the potential fire hazard of all of the ground current for a device flowing along the thin gauge shield wire.

If a single common point ground can't be implemented for practical reasons, the bonding wires between negative connection buses should be far heavier than current-carrying capacity would otherwise dictate. The enemy is voltage drops due to resistance between grounding points - which will become a problem long before the bonding wires are overloaded.

Finally, from a reliability standpoint, not connecting all the ground leads to one common point can result in more than one device failing when a high resistance fault develops in a shared ground lead, which may present itself only when heavy current is drawn on that ground. Example: you sound your horn and your chart plotter reboots.

[tarian]

Originally Posted by er9

I'm curious where should negative wires from lights, pumps, electronics etc on the DC side of the distribution panel be connected to ideally?

Are negatives coming from lights, pumps etc...usually connected to a bus bar thats connected to the engine or a bus bar that connects directly to a negative battery terminal?

currently all these negative wires on my boat are connected to the negative post on the back of the voltmeter thats at the panel.

As stated in many good posts above , you will lead all negatives to busbars , which can be linked with appropriate gauge of wire to a main negative wire going back to the battery this creates a full circuit and has less problems with interference.
rate your busbar to the amps of the devices , I would imagine a 150amp busbar is adequate for most I have 4 busbars rated at 150 amps each taking all my negatives interlinked to feed back to the main.
This includes all fans, all usb outputs , courtesy , led lights on stairs ,and navigation, etc,

[tarian]

Originally Posted by jhulmer

I'm currently rewiring my boat and after many hours of researching CF and other sources, this is what I decided to do.

This is much easier to connect, alter and trouble shoot. It's a work in progress but you can get the idea.

Use the Bluesea terminal strips.

Jim

very nice job

[tarian]

Originally Posted by Terra Nova

The circuit breaker must be installed near the power source--not the load.

Yes this is a must you must protect the wire especially on a long run and a power hungry item like a winch , as said before my camper went up in flames due to a bad electrical fault , no fuse, and wire shorted , enough heat to burn a hole through the metal. (I didn;t do the wiring but I learned how to after that )

[Wotname]

Originally Posted by coopec43

This thread is quite timely.

...........

I have installed a 24V 100A switch for the + winch cable on the instrument/fuse panel. Was that really necessary? (I have also installed a circuit breaker near the winch)
...........

As others have posted, the circuit breaker must be placed close to the source, not near the load.

The switch is necessary and should be placed where convenient.
The purpose of the switch is to prevent inadvertent / accidental / unintentional winch operation; usually the winch is turned on only when needed. Circuit breakers do not make good switches, their mechanical cyclic life is quite low (especially when compared to the cycle life of a switch).

There are of course some designed as a combined "circuit breaker and switch" which do have a high cycle life; typically they look like lever or toggle switch but of course they still need to be located close to the source.

[coopec43]

Originally Posted by billknny

This shows a very basic, and very common, misunderstanding of what a circuit breaker or fuse is for. It is to protect the WIRES not the device.

Yes of course you are right

It is a couple of years since I installed the winch and now I am starting to wire everything up. I am following the manufacturers instructions meticulously so I won't make a mistake but I know I have installed a switch near the winch (as per manufacturer's instruction)

I've got it! (Just read the manufacturers instructions).

Solenoid Installation

WE RECOMMEND THAT THE SOLENOID IS INSTALLED IN AN UPRIGHT POSITION WHERE IT HAS MINIMAL EXPOSURE TO SEA WATER AND IN CLOSE PROXIMITY TO THE ELECTRIC MOTOR OF THE WINDLASS.

Circuit Breaker (Must be fitted to ensure warranty)

If the windlass is overloaded or stalled the circuit breaker will automatically cut power to the windlass and protect the wiring and motor. The circuit breaker should not be used as an isolating switch.

So I was right to install the isolating switch on the instrument panel.

Now where do I install the circuit breaker? Under the floor boards near the battery? But looking at one of the manufacture's drawings of a motor boat it looks like near the helm (that's not going to happen on my yacht)


Thanks for your advice.

Clive