Bilge pumps with digital switching

[mcarthur]

I asked over on trawlerforums, but realised that people here may have advice as well...

I'm rewiring for some digital switching - lights and things - and thought that while the digital switching aspects aren't particularly needed for bilge pumps (ie. nice-to-have switch things on/off from anywhere), the other benefits of bilge on/off counting, counting hours/mins on, and getting notifications through N2K offsite are pretty good.

So since I am re-wiring circuits anyway, changing the extremely sub-standard bilge wiring/system out isn't anything extra. There's was no digital switching in the boat either.
But in re-wiring I'd like to reduce the 2x8 sizeable positive wires (4 bilge pumps per side on a catamaran) to just 1x8 if possible. I can't think of any way of doing it - anyone?

I've tried to do diagrams of options I can think of... only the last (option 4) actually makes use of the digital switch unit's abilities, but still needs two sizeable positive wires for auto + manual, although that could be reduced using a relay like option 3. But option 4 does put always-on power through a digital switching unit rather than a bus bar; that's a little riskier compared to the simplicity of a bus bar, but perhaps not by too much.

Has anyone a CZone or mPower that incoporates manual and automatic bilge pumps? Any ideas?

Essentially I'd like, for 8x bilge pumps along with 8x water-detectors:

• "automatic" operation based on water-detection next to pump
• "automatic" also counts number of times it's come on, and how long each event was.
• "automatic" also can (optionally) send a message to mobile phone (we already have N2K gateway so really just need the data onto N2K and the rules implemented on when to send)
• "manual" mode where a switch turns each one on/off.
• Both "automatic" and "manual" can turn on an audible and visible alarm (again, N2K is fine to handle this if the data can be put there)
• Only 1x positive and 1x negative to each bilge pump area (pump + detector)

[Matt Johnson]

Option 4 is how we're wiring ours. But we're using bilge pump triplex wires, so all three are in one sheath.

[mcarthur]

Thanks Matt, good to know. Excellent idea for the triplex.

I also realised there's another option - run a small wire to the water detector and back to the digital switch unit, but in mPower this would be an input and can be detected by the switch by voltage, hence only needs to carry an amp or so (detector only draws 0.004A). The digital switch could then either manually or through the digital input voltage detect from the water detector then open the breaker to the main pump wire.

This would mean two small 16-17AWG wires - to the water detector and back - and one larger +ve and -ve for pump power. At the expense of one additional smaller wire, I get full digital switching for auto and manual pumping, and still only 2 larger wires with no relay involved. Yes, it exacerbates the reliance on the digital switch being "up" (not hit by lightning, etc.), but even bus bars and wires can fry when lightning hits so anything is up for grabs...

[smac999]

I would go #2

I would not run the auto power from the czone. take it direct from the battery or bus. the pumps are too important to have running through failible electronic controls. you can take the manual from it. when the auto turns on the manual output gets 12v so it should still count that way, you can test that. and you get digital switching for the manual pumps.

the auto would never be turned off anyways so no reason to have digital switching.

if you do choose to use the czone for the auto. take the pumps from different modules. like 2 from each hull to 4 different modules. so a module failing doesn't stop all the pumps or all the pumps in one hull.

[mcarthur]

Oh, good idea for the separate modules if we go digital for the auto! Thank you.