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Author Topic:   Secondary Power Distribution Wiring
nats posted 06-16-2010 08:50 PM ET (US)   Profile for nats   Send Email to nats  
The [audio entertainment device] I want to install has a red (hot) [postive] and a black (ground) [negative] wire. Can I get power to the [audio entertainment device] if I wire directly to the switch on the dash [which apparently is marked with the legend "STEREO"]? Or do I need to go to the power strip inside the console?
davej14 posted 06-17-2010 02:49 PM ET (US)     Profile for davej14  Send Email to davej14     
Depends. If the stereo switch is double pole it will likely have power and neutral run to the switch and you can just connect to the switch. If it is a single pole switch then you will have to run one lead to the neutral common located somewhere in your boat in addition to the stereo switch.

If you eliminate the in-line fuse in your radio lead then be sure to replace the fuse for the branch circuit that powers your stereo switch with one of a similar rating. If the stereo switch is not on its own branch circuit then leave the in-line fuse in your radio lead.

jimh posted 06-17-2010 08:34 PM ET (US)     Profile for jimh  Send Email to jimh     
Most secondary power distribution panels have a battery negative bus which is used to accumulate and connect the many negative power branch circuits. If a power control switch has the battery negative wired to the switch, this circuit is typically only provided to illuminate a lamp in the switch circuit. It is not intended as a place to wire secondary loads.

You can wire the positive feed to a secondary load to the switch that is intended to control that load. The recommended wiring practices for small boats is described and illustrated in an article in the REFERENCE section.

jimh posted 06-17-2010 09:04 PM ET (US)     Profile for jimh  Send Email to jimh     
I do not see much value (or even much logic) in connecting devices which have their own ON-OFF switch to a secondary branch circuit which is controlled by its own ON-OFF switch. This is especially true of modern electronic devices where the ON-OFF switch is actually an electronic switch, and, if the there is no power supplied to the device, the switch loses its memory of what state it was in and reverts to OFF. All this does is require that you turn on two switches to get the device to transition to the ON state. If you want to have a device where you have to turn two switches to ON in order to power the device, then wire the device to a branch circuit with a power control switch. Otherwise, wire the device to the secondary power distribution bus.
Jerry Townsend posted 06-17-2010 10:46 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
I don't see an absolute need in the switch redundancy - BUT - using a secondary branch circuit switch - makes that switch a "master" - turn it off and all components connected to that branch circuit are switched off. --- Jerry/Idaho
jimh posted 06-17-2010 10:57 PM ET (US)     Profile for jimh  Send Email to jimh     
Jerry--I agree that a master OFF switch for a branch circuit can be handy if you have several devices connected. If only one device is connected to the circuit, having two power switches wired in series seems a bit illogical. It wouldn't be as bad if the device had a mechanical type power switch which remembered its state even when the power was off. So many of these modern devices have electronically operated power switches. If you turn off the power to the device, the device also turns itself off. The next time power is restored to the branch circuit, you have to turn the device back on, again.

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