I'm running a 12v bilge pump on a 24v system

[coopec43]

Several people have mentioned the lighter winding with a 24V bilge pump as opposed to a 12V bilge pump. (I have no problem with that)

Why is a Rule 12V 3700gph bilge pump the same weight and size as its' 24V version? That bewilders me.

I was interested to see how one volt difference in battery charge made a significant difference to pump performance.

Also how head height affected pump discharge so significantly. Since my Rule 3700 gph pump would have to lift the water over 8ft I can only expect the pump to discharge 1200 gph (not the 3700 gph claimed on the box)

[cal40john]

Half the cross sectional area, TWICE the number of windings.

[coopec43]

Originally Posted by cal40john

Half the cross sectional area, TWICE the number of windings.

Thanks for that John. (I'll accept your advice as I think I have more important/pressing matters to deal with.)

[hellosailor]

"Why is a Rule 12V 3700gph bilge pump the same weight and size as its' 24V version? That bewilders me."
Could be that in order to have everything else fit the way assembly, the 12v version simply uses heavier wire (anticipating hiher current) and the 24v version is not made-to-measure, but rather, it uses more thinner wire and simply still fills the armature.
Must be some other seemingly arbitrary choices that could result in "the same" stuff.

[rlevin73]

You are going to burn out the motor for that bulge pump
Electrical devices are designed to operate at a specific voltage and current. If you exceed those design criteria you risk burning out the motor and potential fire risk from overheating.

[leftbrainstuff]

Originally Posted by Fuss

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??

It will run for a while but the increased speed will impact bearings and possibly torque the impeller on the shaft. In short that pumps life will be reduced.

You'll also negatively impact your electrical system. Current and arcing will be significantly out of spec. Heard of ohm's law? It's kind of important.

A bilge pump is a piece of safety critical system. Running it out of spec will negatively impact its reliability.

You already know the answer to your question.

[grootsee]

If nothing else, this thread makes for hilarious reading.
A lot of folk out there who I hope never go near electrical design and installation. If you don't have a good grasp of the basics, stay well away from electricity...it doesn't give second chances !!!

[stevenkorson]

Surprised no one has suggested wiring a second identical pump in series. Each pump should then see 12 vdc.....

[paul2884]

Originally Posted by coopec43

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?

It might work very well for a while.


Power = Voltage squared / Resistance



So double the voltage you produce 4x the power (a bit over simplified but you get the idea). Most things will get pretty hot at that stage and if you run it for an extended period - say with a hole in the bottom of the boat? Fully loaded pumping at full capacity in time it will fail.

[Hulda]

Running a 12 volt motor on 24 volt will result in overheating and failure. Wiring in a 12 V system is larger than in a 24 V system (larger 'gauge wire' think you say in US). Thus allowing at larger current to pass. That's why.

[coopec43]

Originally Posted by Hulda

Running a 12 volt motor on 24 volt will result in overheating and failure. Wiring in a 12 V system is larger than in a 24 V system (larger 'gauge wire' think you say in US). Thus allowing at larger current to pass. That's why.

Is that why a 12V Danfoss compressor won't work on 24V?

The electronic unit is a dual voltage device. This means that the same unit can be used in both 12V and 24V power supply systems. Maximum voltage is 17V for a 12V system and 31.5V for a 24V power supply system

[cal40john]

Originally Posted by coopec43

Is that why a 12V Danfoss compressor won't work on 24V?

The electronic unit is a dual voltage device. This means that the same unit can be used in both 12V and 24V power supply systems. Maximum voltage is 17V for a 12V system and 31.5V for a 24V power supply system

Maybe you should contact Danfoss!

Typically there are multiple windings in a dual voltage motor that you wire in series or parallel depending on the supplied voltage, here is a link to a DC motor showing that you wire the the two sets of windings in series for the high voltage, and in parallel for the low voltage.

There will be a compartment covered by a plate where you change how the motor is wired.

Changing from series to parallel you effectively double the windings and half the resistance (double the cross section area of the wire).

http://apps.motorboss.com/connections/2286.pdf


Since it says electronic unit it could possibly also have a switching power supply to boost or buck the voltage with very low losses.

[coopec43]

Originally Posted by cal40john

There will be a compartment covered by a plate where you change how the motor is wired.

Apparently the motor senses the input voltage and switches to 12V or 24V mode automatically. (No change in wiring necessary at all)


Many motors are dual/multiple voltage.

Coincidentally most Treadmills use a 80-260 VDC motor with a suitable HP rating and a PWM motor speed controller to allow the user to change the belt speed and keep a good constant speed and torque while running on it
https://www.instructables.com/id/Use...M-Speed-Contr/

[Wireless1]

By running the 12 volt pump on 24 volts haven't you potentially doubled the motor's speed, while at the same time halving its torque?
Torque; that which does the real work of pumping the water?

[coopec43]

Originally Posted by Wireless1

By running the 12 volt pump on 24 volts haven't you potentially doubled the motor's speed, while at the same time halving its torque?
Torque; that which does the real work of pumping the water?

I don't claim to be expert in this area so I can only "cut and past" what the experts say

Apparently the speed will double in a no-load situation but I disagree with the rest of your comment (for reasons stated earlier in this thread)