Bilge pumps with digital switching

[mcarthur]

Wiring a bilge pump with separate water-detection switch is relatively straightforward:

• +ve wire from unswitched to water-detection switch, water detection switch to pump (aka "auto")
• +ve wire from switched panel to off/on manual bilge switch, then straight down to pump (aka "manual")

ie. 2x positive wires at 3% drop, with one negative return from pump. That negative could just go to ground depending on your electrical configuration, but we are aluminium hulled so is a return.

Bringing in digital switching adds some more options (we're using Maretron mPower, but Czone and others should be the same).

My thought is that there's the main +ve to the digital switching unit (75a unit in our case). One of the lines off the unit is "manual" line down to the pump"(second dot point above).
Now the "auto" setting could just go straight from battery, but really it could also go off the digital switching unit just before the main +ve connects to the unit. This would be nice as both +ve lines would come from near the same point (the digital switching unit) making them easier to run.

Now those wires are decent sizes for the 3% drop, so rather than run 2x +ve and 1x-ve, it would be nicer to run 1x+ve,1x-ve and 1x"control". However, as far as I can work out this would mean a relay near the pump, which doesn't seem a good idea.
Is there any other way?

Now you may think it's a bit silly to worry about one more wire, but as a catamaran with separate areas, we have 8x bilge pumps. So instead of 16x 10gauge +ve wires I would only need to run 8x 10 guage + 8x "control" say 16gauge.

But...one of the nice things about the digital switching unit is that it a) detects and send to N2K any amperage going through the switches, and b) detects "blown bulbs" and other anomalies in the different switched circuits. So if wired properly I could have an N2K detection of the automatic bilge pumps, counting number of turn-ons, hours on, etc.

I've been looking at this for some time, but my brain is still mush on how to get 8x auto and manual bilge pumps connections from the digital switch unit (which has only 12 switches). I feel there's a fancy way, but I'm not seeing it!

 

[Hyperion]

Are you trying to switch them on remotely without having to run wires back to the helm for each one? Does your existing digital switching system not take care of this already?

 

[ksanders]

I like automation.

I also like the simplicity of a float switch directly controlling my bilge pumps.

I also like the idea of zone water detection and alarming based off of that.

But... I like not needing any other thing in the circuit with my bilge pumps.

 

[mcarthur]

I'm rewiring for some digital switching - lights and things - and thought that while the digital switching aspects aren't particularly needed (ie. 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.

I've tried to do diagrams of options I can think of... only the last actually makes use of the digital switch unit's abilities, though could possibly be combined with option 3's relay.

 

[mcarthur]

I like automation.

I also like the simplicity of a float switch directly controlling my bilge pumps.

I also like the idea of zone water detection and alarming based off of that.

But... I like not needing any other thing in the circuit with my bilge pumps.

Thanks, I do agree. But perhaps I'm lured by the chance to get the notifications (including when off-boat), count and hours. I priced out other options just for counters of on/off and hours, for 8 bilges, and that alone was equal to using the digital switch unit. That doesn't even count for the N2K notifications (inc offsite) and that the unit can do 12 switches and I've only got 8 pumps so there's a few other always-on items I can run from it (yes, N2K then becomes always-on as well but I've got lots of battery).

 

[Hippocampus]

Just wondering could you do the wiring old school and as simple as possible. Then add a bilge hour counter(s) to get history and detection if one goes on.
A prior boat had Phillipi and that was possible with that system to my recollection. I just wanted a red light to go on at each steering station and nav for each low and high water pump. Never put in counters but it was available.
You mentioned above you could do it that way and it maybe best. believe it was shunts so failure had no effect on function. Just meant a light didn’t go on.

 

[Bmarler]

The whole idea of using the digital switch is to have n2k functionality right? That makes option 4 the best choice in my view. As long as the digital switch has sufficient headroom to run all the pumps simultaneously anyway.
Id imagine there are relay outputs within the digital switch, making the extra relay unnecessary.

 

[Bmarler]

Looking at the diagram again, the manual switch should just go to the pump unless you want to have manual/off/auto functionality with a standard three way switch for pump control. If wired that way you’d need to be sure to only activate the auto position on the manual switch in the event of the digital switch being turned off or disconnected.
That strategy, however, gives you the option for redundant automatic operation should you want to shut down the n2k network for some reason.

 

[sunchaser]

Mac
Does each bilge pump have its own breaker at the central panel? If so could you not monitor operating time at that central location with each pump having its own level switch, float or otherwise?

Is the vessel making water in a few areas requiring careful monitoring? Possibly these “problematic” through hull areas should be your focus.

 

[ksanders]

Thanks, I do agree. But perhaps I'm lured by the chance to get the notifications (including when off-boat), count and hours. I priced out other options just for counters of on/off and hours, for 8 bilges, and that alone was equal to using the digital switch unit. That doesn't even count for the N2K notifications (inc offsite) and that the unit can do 12 switches and I've only got 8 pumps so there's a few other always-on items I can run from it (yes, N2K then becomes always-on as well but I've got lots of battery).

and if the digital switching unit goes out you have no bilge pumps.

That is a very dangerous situation to put your boat in.

The key to reliability is avoiding single points of failure

 

[mcarthur]

True on the reliability, but there's three reasons why electrics and electronics typically fail on boats: incorrectly spec'd and built wiring and fusing, corrosion, and lightning.

I'm making sure the first and second are ok by renewing the wiring and fusing. The third is beyond "ensuring" as it's in the lap of the gods so to speak - there's little you can do as the evidence is still, after many many years, not clear on how best to mitigate the problem. You cannot FIX it, but there are multiple ways to reduce it - not being on a boat being the most successful .

So really, there's probably as much chance of the wiring and bus bar stopping working as the digital switch unit (and it's wires). So I reckon I haven't noticeably increased risk from the usual way of wiring

 

[ksanders]

True on the reliability, but there's three reasons why electrics and electronics typically fail on boats: incorrectly spec'd and built wiring and fusing, corrosion, and lightning.

I'm making sure the first and second are ok by renewing the wiring and fusing. The third is beyond "ensuring" as it's in the lap of the gods so to speak - there's little you can do as the evidence is still, after many many years, not clear on how best to mitigate the problem. You cannot FIX it, but there are multiple ways to reduce it - not being on a boat being the most successful .

So really, there's probably as much chance of the wiring and bus bar stopping working as the digital switch unit (and it's wires). So I reckon I haven't noticeably increased risk from the usual way of wiring

You are telling yourself it's reliable enough. Circular reasoning will always provide the answer you want.

My opinion as a guy that spent a very long career thinking about the reliability of electrical and electronic systems.

Avoid single points of fainure. To do this look at any particular component and imagine it failing. What are the results. Not just the direct results, the ripple effect. Then take action to mitigate that risk.

You are going to do what you are going to do, and that's OK. All I can say is for me, my boat, I have completely separate pumps and wiring, along with backup systems for critical things like bilge pumps.

and... Separate monitoring systems in place as well.

 

[mcarthur]

Thanks Kevin.
Definitely listening (no point in asking if you aren't willing to listen to sensible, logical and experienced advice!).

Would you know how the modern boats with digital switching (Czone, etc) do it to minimise the risk?

 

[READY]

No direct knowledge of how new boars build in redundancy but based on assisting Airstream trailer owners with issues with czone it seems if c-zone fails their camping trip will likely end. I have a 2018 model with old school controls and like it that way. Admittedly a failure on a trailer is not as likely catastrophic compared to a boat but I would hate to not be able to work around a failure.

for your multiple pump scenario if you want monitoring I would maybe just put them all on one bus and then monitor current with a smart shunt on that bus. You wouldn't have individual monitoring of each pump but you could easily remotely monitor total consumption and extrapolate from spikes.
For me that would be "good enough" and unless the shunt failed would not create new points of failure nor significant complexity.

 

[rslifkin]

Relays are also useful for monitoring. I've got a pump that's alarmed as a high water alarm (it's the second level pump in the engine room). It's wired as normal, but the float switch also triggers 2 relays. 1 with a 5 second delay that triggers the audible bilge alarm (delay is to prevent beeps if the float bounces) and the other with no delay that closes the contacts on one of the digital inputs on the Victron Cerbo. When that happens the Cerbo sends an alert to my phone warning of the high water situation.

Nice simple setup and a failure of the monitoring doesn't impact pump operation.

 

[Iggy]

Personally, I would not add digital switching to an older boat. Way too much rewiring. But I do like the concept!

I did install this on my boat. Individual Remote Boat Monitoring Products for Marine Vessels — Blue Guard Innovations I pulled out the Siren Marne system. Siren wants $225 a yr and Blue Guard is 60 yr.

Point being that ether one will text and e-mail you if your pumps turn on. But Blue Guard has more options for this and more.