Electrical question...

[Captain Crisp]

I've just installed a Seaflow auto bilge that runs for a second every 2. 5 minutes... Assuming the bilge is dry, it would run for about an hour in total per week...

It draws12 volts 2.5 Amps...

How long before my battery is flat?

(failed my Maths A Level for context)

Relevant pics below (wiring is work in progress)

Thanks!

 

[billskip]

About 5 months

 

[Sticky Fingers]

Why does it run at all if the bilge is dry?

 

[AngusMcDoon]

Why does it run at all if the bilge is dry?

It needs no float switch. It does a test run periodically and by measuring the current consumed decides if it is pumping water or not.

 

[Sticky Fingers]

That would drive me mad. Far too complicated, makes a noise every minute, plus it flattens your batteries.

 

[billskip]

That would drive me mad. Far too complicated, makes a noise every minute, plus it flattens your batteries.

??? Could be on his boat 30 miles away ...
Anyways it's every 2½ minutes...

 

[Sticky Fingers]

Regardless, seems like a poorer solution to a problem that was already solved by the float switch….

 

[Aeolus]

If you've a single 80Ah battery, then 16 hours of bilge pump operation would use 50% of your battery capacity. It may damage the battery if you allow it to go lower than that. At 1 hour operation per week, you have approx 4 months by my reckoning.

 

[ylop]

That would drive me mad. Far too complicated, makes a noise every minute, plus it flattens your batteries.

Float switches can jam / fail.
Float switches may take up space in tight places.
Float switches often leave more water in bilge than these.
So, for some applications, some people prefer them. They aren’t new so presumably enough people buy them to make it a viable product line.

 

[Captain Crisp]

Regardless, seems like a poorer solution to a problem that was already solved by the float switch….

Unfortunately there's no room for a float switch and pump in the bilge sump, the good news is I can turn it off, when I'm on board.

 

[Sticky Fingers]

Float switches can jam / fail.
Float switches may take up space in tight places.
Float switches often leave more water in bilge than these.
So, for some applications, some people prefer them. They aren’t new so presumably enough people buy them to make it a viable product line.

That’s all true, the jam/fail argument seems to be counteracted by the increase in complexity of the alternative IMHO.

Unfortunately there's no room for a float switch and pump in the bilge sump, the good news is I can turn it off, when I'm on board.

Fair enough

 

[billskip]

If you've a single 80Ah battery, then 16 hours of bilge pump operation would use 50% of your battery capacity. It may damage the battery if you allow it to go lower than that. At 1 hour operation per week, you have approx 4 months by my reckoning.

Well the "one second" would have a high kick in spike and a low run demand ( not under load) which I would think to be less than 2.5amp demand per second, taking all other possible losses (theory against practice) I made a guesstimate time.

 

[Poignard]

Hopefully, when the leak via your sterngear is stopped, you won't need an automatic bilge pump

 

[Irish Rover]

I have one of these in my tender - I posted a thread about it last year. They have to be the most stupid design of a bilge pump ever. I haven't got around to replacing it yet, so I had to disconnect a battery terminal to stop it discharging the battery over the winter when I rarely use the tender.

 

[Poignard]

As the OP has installed the pump, he isn't likely to get a refund if he tried to return it.

To prevent it cycling on and off continually, perhaps a 12v float switch could be wired into the pump supply so that it only becomes active when there is a certain level of water in the bilge sump*.

*The Twister has a deep bilge sump about the size of a shoe box below the front of the engine into which the float switch could be fitted.

 

[Captain Crisp]

As the OP has installed the pump, he isn't likely to get a refund if he tried to return it.

To prevent it cycling on and off continually, perhaps a 12v float switch could be wired into the pump supply so that it only becomes active when there is a certain level of water in the bilge sump*.

*The Twister has a deep bilge sump about the size of a shoe box below the front of the engine into which the float switch could be fitted.

There's not enough room in my sump for a pump and a switch... I've reassembled all the stern gear stuff, so hopefully all this will be purely academic... Also, French's have said they'll repair my prop for £85!

Now for the blinking woodwork....................