Installing MFD

[MikeM]

OK...I've got my new Raymarine A98 MFD. I'm going to put it on the flybridge, and I have a few installation questions.

1. I found an unused 12V power wire on the flybridge. It is powered from the main DC panel. There is nothing else powered from this breaker as far as I can tell, but it appears that its corresponding ground wire is being used on another circuit...a 12V outlet, the horn, and the FB VHS.

So my plan is to use the power for the MFD and eventually an AIS transceiver. Can connect the existing ground to a bus bar to ground all of these components?

2. The MFD power and data cable has a red positive, black negative, and a thin black shield (drain) wire. This is supposed to be connected to the RF ground point. The directions state that on vessels without an RF ground system, the shield wire should be connected to the negative battery terminal.

I don't know if I have an RF ground system. How do I figure that out?

Thanks in advance for the help?

Mike


Mike Metts
KK 42-165
Virginia Beach, VA

Sent from my iPad using Trawler Forum

 

[DavidM]

Using another ground wire, particularly one hooked to the horn may be a problem. If you use it and you hit the horn, the additional current drawn by the horn may cause enough voltage drop in the ground wire to cause your display to drop out.

The positive wire you found is almost certainly part of a twin conductor cable. Follow it back and see if you can't find its ground. Otherwise, run a new ground.

Your boat, unless you have a SSB radio, does not have an RF ground. Run the shield to the ground buss near the battery.

David

 

[MikeM]

Using another ground wire, particularly one hooked to the horn may be a problem. If you use it and you hit the horn, the additional current drawn by the horn may cause enough voltage drop in the ground wire to cause your display to drop out.

The positive wire you found is almost certainly part of a twin conductor cable. Follow it back and see if you can't find its ground. Otherwise, run a new ground.

Your boat, unless you have a SSB radio, does not have an RF ground. Run the shield to the ground buss near the battery.

David

Thanks David. I think the ground wire I found is part of the twin conductor cable that runs with the power wire I found. It comes out of the same wire bundle and is the same gauge. It is spliced to provide a ground for the horn/VHS. Do you think I should still run a new ground wire?

I do not have a SSB. So then I just run the shield to the same ground buss as the ground wire?

Thanks, Mike


Mike Metts
KK 42-165
Virginia Beach, VA

Sent from my iPad using Trawler Forum

 

[DavidM]

Try it and see if it works. But a horn is a fairly large DC load- 5 amps or better and causes lots of interference when it goes off due to the magnetic actuator in the horn which results in lots of voltage spikes. Your MFD may not be happy with the resulting voltage drop and spikes.


But you are going to need to run a shield ground back to the ground battery buss anyway. Why not run a new ground at the same time for the horn/VHF and use the two conductor cable strictly for your MFD. That will give it clean power.


David

 

[MikeM]

David,

That sounds like a good idea. But I'm still a bit confused about this shield wire. From your response, I take it that I couldn't just connect it to a ground wire that goes to the negative battery buss. It sounds like it needs to be a separate wire all the way to the buss on its own. Do I have that right? If so, I will take your advice and run a new ground for the horn while I am running the shield wire.

Do you see any issue with putting an AIS transceiver on the same circuit as the MFD.

Thanks, Mike


Mike Metts
KK 42-165
Virginia Beach, VA

Sent from my iPad using Trawler Forum

 

[Tomsmb]

Mike
Run a fairly hefty wire, like a 10AWG from the main ground bus to a convenient location near your new installation and install another small buss for connecting items such as these as you add them. There is no problem grounding the AIS to the same location. The shield wire can also go to that buss. If you add an SSB or Ham radio in the future you will have to address shielded grounds then.

Have fun.
Tom H

 

[MikeM]

Mike

Run a fairly hefty wire, like a 10AWG from the main ground bus to a convenient location near your new installation and install another small buss for connecting items such as these as you add them. There is no problem grounding the AIS to the same location. The shield wire can also go to that buss. If you add an SSB or Ham radio in the future you will have to address shielded grounds then.



Have fun.

Tom H

Thanks Tom. Sent you a PM.


Mike Metts
KK 42-165
Virginia Beach, VA

Sent from my iPad using Trawler Forum

 

[DavidM]

I thought about Tom's suggestion of establishing a new ground buss at the upper helm. That is fine for power, but I believe that electronics RF shielding should go to the source- the primary DC ground buss. Grounding it at the helm will probably work and I have done the same thing myself and have gotten away with it, but it is better to have a separate ground to the primary buss for RF shielding, and so does Raymarine.


David

 

[MikeM]

Thanks David. I am going to work on this today.


Mike Metts
KK 42-165
Virginia Beach, VA

Sent from my iPad using Trawler Forum