This should be considered a "feeder" improvement project; one which is necessary to accomplish other projects. In this case, I plan on installing Radar and other electronics that have a significant power requirement. A branch circuit to power these devices is in order.
The first task is to assess the power requriements of your nav system, along with any anticipated future additions. I have determined that there is an existing 10AWG circuit to the helm, installed by the factory, but this will not be sufficient for the additional electronics I will be installing - so I am going to need an additional 8AWG branch circuit. I will be wiring the branch circuit from the main DC distribution panel to the helm area.
At this point, you may want to review the technical requirements for high-power DC circuits:
The DC branch circuit consists of a marine grade duplex 8AWG cable, approx 18ft long. It connects to a 20Amp DC breaker in the main distribution panel. This panel is fed from the batteries, so it is the preferred location to pick up a high current source. At the helm side, I will be adding a 6 circuit distribution panel, with fuses for each device. In addition, to ensure a satisfactory signal ground for the radios, an additional 8AWG line is connected from the boat's main DC bonding ground to the helm. Finally, a 6 bank distribution switch will be added for controlling the various devices and networks that will be installed.
The photo here shows my main DC panel with the cover removed, exposing the breaker connections. The first order of business is to punch a hole in the electrical chassis with a "Greenlee Punch" to enable running the new wiring to the helm. If not obvous, you should turn off the main DC breaker before accomplishing this task. Running the wires is pretty straightforward, however, you may wish to review my thoughts on wiring and terminating at this point. Wiring, Splicing, and Pulling Cable Through a Boat.
A suitable location needs to be found at the helm for the distribution panel. The ideal location would be out of the weather. On this boat, there are not too many areas that fit this requirement. After removing a kick panel in the forward locker, I decided that this location, directly behind the helm, woud lend itself to the installation of a wiring board.
Once the wiring is fed through the boat, I built the wiring board to include a sub-fuse panel for the electronics devices, along with terminal strips to interconnect the devices, such as NMEA 0183 interconnections for the GPS and VHF DSC radio. I took care to ensure I could remove this board should I ever need to service the saucer TV antenna. For this reason, I routed all of the wiring to the front of the board so the wiring would not inhibit moving the board out of the way. I also left plenty of room at the front of the panel for installation of future navigation components.
The distribution switch panel was installed on the Starboard side, next to the helm seat, and wired into the wiring board. Attention must be given here too in regard to DC voltage loss, so sufficient AWG wiring must be used. For this reason, I used 12AWG wiring for this run. The panel is made by BlueSea, and have nice little labels for the various functions. Unfortunately, only a few labels come with the panel, but you can order them individually from BlueSea. In addition to that, you can have custom labels made as well, but at $5 for each label, this tends to become expensive. However, I did exactly that for the right-most three labels (I see now that "AIS" is a standard label you can order, so BlueSea likely adds labels as new devices become available). Doing a "professional" job just makes you all the more proud of your accomplishments, I think.
The electrical panel is actually behind this kick panel. I installed an 8in dia deck plate in front of the fuses so that I could access them without having to remove the kick panel.
After the kick panel is re-installed, the deck plate cover is screwed on, resulting in a rather protected electrical wiring panel. The kick panel is actually one side of the storage bin where we typically store our life-jackets. With straps and buckles flying around, you do not want to risk the chance of shorting anything out from them.
If possible, look for a unused spare slot for the new circuit at the boat's main DC distribution panel. You should not double up on an existing breaker, but rather install a dedicated breaker for this purpose. Only after all of the wiring is completed should the breaker be installed at the main panel. Comparing this photo with the first photo above, you can see where I added the feedthrough for the cable.
The last step is to tie a distribution block at the helm back to the boat's DC system bonding grid. This is often required for proper - or better operation of the radio antennas.
Optionally you may want to consider adding an engine starting isolator, such as Newmar's StartGuard, which essentially maintains voltage during engine starting. In some setups, if you turn the nav equipment on before starting the engine, the voltage will drop sufficiently during engine starting to shut the equipment down. Devices such as the StartGuard prevents this by augmenting the supply voltage during engine starting.
BlueSea Label Order Form (standard labels)
BlueSea Custom Label Order Form