Separate power supply for Plotter, VHF & AIS?

Bertie1972

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My new-to-me Bavaria has the VHF and plotter on the same panel switch. I’m currently adding AIS and although it seems attractive to have it powered from the single ‘instruments’ switch as well, I suspect all three should be on a separate circuit. Wiring is NMEA 0183.

Could the team advise please?
 

prv

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You need to ensure that all the things on a shared circuit don't add up to more than the circuit's rating, but it's very unlikely that an AIS transmitter would be a problem in this case and practically certain that a receiver wouldn't. Beyond that it's just a question of ergonomics, what makes sense for you to switch on and off together. I have my plotter and VHF on separate switches because I used to leave the plotter off in familiar waters (nowadays I tend to flick everything on even though I don't really need it...) but it makes no difference electrically.

Pete
 

halcyon

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How likely is a supply fault? If you follow your logic, every single item of electrical equipment would need its own breaker/fuse.

Bit like, why do I need air bags in my car, odds on you will never need them, but the day your VHF, plotter and AIS stop working in the middle of the channel in a gale you know..

You need to decide what is critical to safe sailing and what is a convenience to sailing.

Brian
 

Norman_E

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My boat came with two circuits on the main switch panel labelled for instruments. I have the VHF and its dedicated GPS on one switch and the NMEA2000 plotter and sailing instruments on the other. If I added AIS it would go on the same circuit as the VHF.
 

PaulRainbow

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It's OK to share a switch, but every circuit needs to be adequately protected. If the multi device switch circuit is protected by a fuse capable of protecting the whole circuit, it's going to be over-rated for the individual device circuits. It is bad practice for multiple electronics devices to share a fuse.

I'd be happy to have a single switch, fused for the entire circuit, which then supplies a fuse board where each device is connected to its own fuse. Technically, there is no need for a switch for the plotter, as it has its own on/off button or touchpad, but it can often be more convenient to have a "navigation" switch, that turns on/off the plotter, N2K network, AIS, wind, depth etc

The VHF is a vital safety device and should, IMO, be on its own circuit. Again, it does not absolutely need a switch, but it must have a fuse.

If i was the OP, i'd connect the AIS to the current switch, but remove the VHF from the switch and just fit it with its own fuse. The plotter and AIS would still need separate fuses. If the switch is a combined switch/breaker, then it needs to be rated for the combined circuit, with individual secondary fuses for each device.
 

SiteSurfer

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I've just added a bunch of stuff to mine, I took the approach that I would continue to use the line for the instruments but break it out near the binnacle (in a dry place!) with a further fused splitter box, every item has its own fused supply from that box including the network etc.

The only one I kept separate was the autopilot as I think that uses a higher amount of power (it may not but it felt right to do so).
 

lw395

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I've been on a few boats where the VHF and/or GPS could be powered by a separate small 12V battery. ISTR this was in RORC regs at one point?
Quite a few years ago, I was on a boat where an instrument problem locked up the whole NMEA network. There was a period where we wished the depth sounder was stand alone!

Whatever problem scenarios you dream up and design around, something different will happen one day.
 

bedouin

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I wonder if the Plotter supplies position data for the DSC on the VHF - so it would be a matter of safety not to have the VHF without the plotter.
 
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