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Old 05-03-2019, 01:15   #1
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I'm running a 12v bilge pump on a 24v system

There is no electronics in in, just a motor.

It seems to work fine and spins faster too.

So I just thought I would ask you experts what I am missing??
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Old 05-03-2019, 01:26   #2
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Re: I'm running a 12v bilge pump on a 24v system

I'd try running a 12V water pressure pump, macerator or oscillating fan on 24V but I would never think of messing around with voltages on such a vital piece of equipment as a bilge pump.
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Old 05-03-2019, 02:11   #3
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Re: I'm running a 12v bilge pump on a 24v system

I would suspect that the pump would draw a lot more current. This means the pump's battery leads insulation would be threatened. Hopefully you have the inline fuse size the pump manufacturer recommends.
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Old 05-03-2019, 04:00   #4
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Re: I'm running a 12v bilge pump on a 24v system

It’s inevitable that the pump motor winding will suffer heat damage and burn out quicker than normal, potentially when you most need it.

You might end up killing someone, yourself included, just to save a few dollars by not replacing it with a proper 24v pump. Bilge pumps are cheap - how do you value the lives of your passengers/crew?
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Old 05-03-2019, 04:23   #5
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Re: I'm running a 12v bilge pump on a 24v system

Quote:
Originally Posted by sstuller View Post
I would suspect that the pump would draw a lot more current. This means the pump's battery leads insulation would be threatened. Hopefully you have the inline fuse size the pump manufacturer recommends.
Maybe I misunderstand you but why would it "draw a lot more current"?
And "leads insulation would be threatened": surely the leads can be lighter for 24V?

I thought the winding of a 24V motor would be a lot lighter than a 12V motor of equivalent power. But why do Rule 12V 3700GPH bilge pumps weigh exactly the same as the 24V version?

I'd worry the pump might spin a lot faster than it was designed to do.If the pump is pumping more water maybe it would overheat?

Maybe I'm wrong?
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Old 05-03-2019, 04:34   #6
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Re: I'm running a 12v bilge pump on a 24v system

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Originally Posted by S/V Illusion View Post
It’s inevitable that the pump motor winding will suffer heat damage and burn out quicker than normal, potentially when you most need it.

You might end up killing someone, yourself included, just to save a few dollars by not replacing it with a proper 24v pump. Bilge pumps are cheap - how do you value the lives of your passengers/crew?
Your absolutely right SV, I read your post and I immediately changed it for a proper 24v pump so that I don't kill anyone.

But now I'm confused , lets say its 2 oclock in the morning and the correct 24v bilge pump has failed, I don't know why it failed , it was only 2 years old and it had hardly had to pump anything over this time...must have been a faulty one...anyway, its 2 oclock in the morning and a storm is raging and some water is coming in from somewhere, I'm holding a 12v bilge pump in my hand.... what shall I do now?

shall I connect it to the 24v system?
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Old 05-03-2019, 04:46   #7
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Re: I'm running a 12v bilge pump on a 24v system

"shall I connect it to the 24v system?"

I wouldn't hesitate to connect it. The pump would probably be under water so hopefully it wouldn't overheat.
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Old 05-03-2019, 05:07   #8
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Re: I'm running a 12v bilge pump on a 24v system

Quote:
Originally Posted by Fuss View Post
Your absolutely right SV, I read your post and I immediately changed it for a proper 24v pump so that I don't kill anyone.

But now I'm confused , lets say its 2 oclock in the morning and the correct 24v bilge pump has failed, I don't know why it failed , it was only 2 years old and it had hardly had to pump anything over this time...must have been a faulty one...anyway, its 2 oclock in the morning and a storm is raging and some water is coming in from somewhere, I'm holding a 12v bilge pump in my hand.... what shall I do now?

shall I connect it to the 24v system?
Better to connect it and give it a try than to do nothing and allow water to continue to come in. Just my thoughts.
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Old 05-03-2019, 06:10   #9
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Re: I'm running a 12v bilge pump on a 24v system

Even better, have the right spare on hand
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Old 05-03-2019, 06:20   #10
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Re: I'm running a 12v bilge pump on a 24v system

24v will double the current and cause 4x the heat load. Assume your windings have 2ohms of resistance then the current load would be 12/2 = 6 amps. Heat load is The amount of amps squared times resistance. Therefore the motors windings must be able to handle 6x6x2 = 72 watts. Double the voltage then doubles the current to 12 amps with a resulting value of 12x12x2 = 248 watts of heat load. That much heat would probably result in damage to the windings of the motor. In the event it was submerged it might take the heat but I would operate it sporadically to allow time for it to cool so you would not lose the last available pump you had.
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Old 05-03-2019, 09:02   #11
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Re: I'm running a 12v bilge pump on a 24v system

without sounding like a bore ,there is a reason why they they are sold as different voltages if you want to run a 12v piece of essential and life saving equipment on a 24 volt system get yourself a voltage dropper and have a separate 12 volt circuit . It is only a matter of time before your bilge pump stops working , and if not fused could damage further along the circuit.
not hard to do and allows for redundancy in your system if you have a mix and match of stuff running both voltages
I have a 24 volt boat and a 12 volt distribution board for all my 12 volt stuff
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Old 05-03-2019, 09:10   #12
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Re: I'm running a 12v bilge pump on a 24v system

Quote:
Originally Posted by Fuss View Post
There is no electronics in in, just a motor.

It seems to work fine and spins faster too.

So I just thought I would ask you experts what I am missing??



So, I've actually done this sort of thing, with 6v fans on 12v systems, and 6v starter motors on 12v systems, and I have various DC motors with controllers that I've fiddled with in the lab and in my workshop.


If you run it at 24v it will run somewhat faster (not twice as fast, at least not while it's pumping water, because of the pump curve), and the water will discharge at higher pressure and somewhat higher volume, and it will be noisy.


In most cases it will eventually overheat and fail, if you run it long enough. How long it will take to fail is hard to predict, might be a minute, might be a few hours, but more probably somewhere in between.


Because the startup torque will be higher, there is a possibility that the joint between the shaft and the impeller will fail, because the joint can only withstand a certain amount of torque. This could happen either right away or after a number of starts.
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Old 05-03-2019, 09:17   #13
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Re: I'm running a 12v bilge pump on a 24v system

You could try a buck converter to step that 24v down to 12.
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Old 05-03-2019, 09:27   #14
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Re: I'm running a 12v bilge pump on a 24v system

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Originally Posted by sstuller View Post
I would suspect that the pump would draw a lot more current. This means the pump's battery leads insulation would be threatened. Hopefully you have the inline fuse size the pump manufacturer recommends.



Wouldn't it draw less current?
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Old 05-03-2019, 09:34   #15
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Re: I'm running a 12v bilge pump on a 24v system

It will work, although it is more likely to eventually fail.
The hopper rinse system on a Thrush crop duster is a rule 12V bilge pump run off of a 28 VDC aircraft electrical system, been doing it that way for decades, however it only has a 20 ish gl tank, so runs for maybe 30 sec? I’m sure if it had to run for an extended period it would burn the motor out.
12V systems operate at usually 14V when charging , 24V at 28V
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