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Old 23-10-2019, 10:47   #1
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NMEA Question

When I purchased my boat it had Raytheon instruments, autopilot and radar. The autopilot was on one panel breaker and the instruments and radar on a second breaker.

I upgraded my electronics a few years ago when I purchased my boat. The installer messed up the power connections so that the Autopilot breaker powered everything in the pedestal and the Instrument breaker powered the Radar. I want to correct this.

In the attached diagram I show how the B&G system is currently connected and how I propose to connect the Raymarine autopilot. On the B&G side, you will see that 12-VDC is injected into the NMEA backbone with a connection up in the pedestal. This power comes from the panel's Autopilot breaker. There is another 12-VDC connection located at the Radar box that comes from the panel's Instrument breaker. I would like to change that so the power is injected at the same point as the power going into the Radar box - placing them both on the same breaker.

Is there any problem with moving the nmea backbone power injection point out of the pedestal?
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Old 23-10-2019, 11:00   #2
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Re: NMEA Question

From a network perspective "above" the radar box tee as shown on your sketch is still the same location, even if it isn't physically. You have 4 devices on one side of the injection and two on the other.

If you install "below" the radar tap then you are changing things slightly, but still only three devices on each side, which should be fine.

Only caveat would be if the pedestal devices are power hungry, check the voltage drop in the NMEA cabling before and after the change. If those devices are the most power hungry on the network, and the length of the trunk from the radar box to the pedestal is significant then you may get significant voltage drop. That would be the only reason I can see to install the injection at the pedestal, the installer could run larger wires outside the trunk to minimize voltage drop, and then inject nearest the larger consumers.

[Edit] just took a look at the Zeus and Triton details, both are 3 LEN on the NMEA network. For voltage drop you want to balance each side of the power injection. Still doesn't mean you can't move the injection, but likely it needs to be "above" the radar box tee to keep the same network loading (I'm guessing that the other devices are lower LEN).

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Old 23-10-2019, 20:06   #3
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Re: NMEA Question

Why is your nmea 2000 bus and seatalk ng bus seperate? How do you get waypoint and heading data back and Forth?

Why do yiu have 3 terminators on the right. And a tee feeding a tee.

You should Join the 2 together. Remove the nmea 2000 power. Remove bottom terminator from both sides. Make cable that goes from. Bottom of nmea 2000 tee to seatalk ng 5way. Then remove that extra tee and terminator in the middle right. you can choose to power the whole thing from whereever. I would power the n2k / stng bus from insterment panel and the acu from pilot breaker. this means the heading sensor and pilot screen will be on if pilot breaker is off. but you want the heading sensor to feed the MDF. there are ways to fix power to pilot screen but who cares if it's one. every boat is now like this.

Now everything on single bus and Will share data from mfd to pilot.

And to be correct. You have a nmea 2000 backbone and seatalkng backbone.

Nmea is a group of people. And seatalk is proobably what you used to have. You have neither of those
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Old 25-10-2019, 14:51   #4
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Re: NMEA Question

As Smac said you can combine the two networks with a cable replacing the terminator in the pedestal. The cable must be made - start with a short blue SeaTalk cable, cut off one end and install a N2K field installable connector. If you want to power the 2 half’s of the network separately leave off the red wire. Or remove the power insertion furthest from the middle based on device LEN.
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