Wiring of bilge pump to thruster battery

[Hydraulicjump]

I lost the float switch on my bilge pump, but the switch in the panel worked fine. Step one was to clean all the goo off the float switch (it had grown some stuff). Step 2 was to check the 5 amp fuse, which turned out to be the problem. All fixed and fine.

But this raised a question: why is the bilge pump wired to the thruster battery and not the house bank? I am thinking through a worst case scenario where the bilge pump(s) are keeping your boat afloat while it is unattended (say, due to a leaking seacock). Wouldn't you want the bigger battery bank to keep it afloat longer?

I am certain there is a rational reason (don't want to have dead house batteries?), but I don't know it.

Jeff

 

[R Baker]

On my 29C the wiring diagram shows both pumps wired to the Thruster Battery. On all my previous boats the pumps were wired to the house batteries. If your boat is plugged in, when moored it probably makes little difference if wired to the thruster battery; however if not plugged in when moored, then I would feel more comfortable if wired to the house bank. The rational of why it is wired to the thruster battery is a bit of a mystery to me as well.

 

[CAPTCRUNCH]

Speaking mostly from ignorance, it seems to me that the more amp-hours available (the house bank) to keep my boat afloat, the better. BUT, I think I can see the logic that it's better to have the pump(s) using a dedicated power source (the thruster battery with thrusters off) than a shared one (the house bank with other competing loads such as the TV, stereo, VHF, fridge, etc. possibly running).

 

[SGIDAVE]

Given that the bilge pump is a piece of EMERGENCY equipment, it serves to reason that it should be connected to the most reliable source of power. This would mean that it should be connected to the largest battery bank.

dave

 

[CAPTCRUNCH]

It would be good to have somebody from FM explain here why they do it the way they do.

 

[Kaisardog]

since some folks like me occasionally accidentally run down their entire house bank by leaving large drain items like the Frig on , it makes sense to wire the bilge pumps to a battery unlikely to be drained , IE the thruster. on my old boat i wired the 2 bilge pumps to the engine start battery while the boat was dockside. since the house bank was feeding the Frig , if power was lost at the dock, the Frig would drain the house bank in a couple days...

 

[knotflying]

I would first make sure you have good insurance from a good insurance company. The bilge pump shouldn't be relied on to save your boat in the event of a leak while unattended. Constant maintenance of the pump, connections and sensor are a requirement. Making sure the cockpit drains are cleared is paramount. I removed the grating because they got clogged too quickly and then the water ran over the gutters into the bilge. Having someone checking on the boat while away is also a good measure.
Sure, more batteries will last longer, but chances are your pump will burn out before the batteries discharge.