24v pump on 12v system?

[Tim Good]

I have noticed (when trying to figure out why my grey water pump wasn't priming correctly) that someone once installed a 24v pump instead of a 12v.

Since my boat is a 12v system then the 24v pump will just run at half power right? Maybe why it can't suck up the water well enough to prime.

Can I just get some sort of setup up regulator to 24v and install next to the pump or am I best to just get a new 12v pump? Like this maybe?

http://www.ebay.co.uk/itm/321520967347

The pump is a Jabsco Utility Puppy 3000 so come in at £300 to replace like for like.

 

[TradewindSailor]

There are devices that will step up DC voltage but you need to make sure they can take the peak current draw of the pump. This one is a 10 amp at 24 v unit :
http://www.ebay.com.au/itm/DC-DC-Vo...-10A-240W-Waterproof-Anti-shock-/170993519990

I don't know if it is any good though.

 

[VicS]

I have noticed (when trying to figure out why my grey water pump wasn't priming correctly) that someone once installed a 24v pump instead of a 12v.

Since my boat is a 12v system then the 24v pump will just run at half power right? Maybe why it can't suck up the water well enough to prime.

A lot less than 1/2 power probably

 

[William_H]

A lot less than 1/2 power probably

If it were a resistive load running on 12v when it is designed for 24volts you would get 1/4 the power becuase you have half the voltage therefor half the current and power is volts X current.
However a motor is very different. When running at full speed a motor tends to partially act like a generator in itself so current is low. When it runs slower the generator is less significant so it draws more current. So your pump will ternd to draw more current than the purely resistive math model.
So who knows exactly how much power it is using (hence pumping) without actual measurement in operation.

Regarding the OP question I think a 12v pump would be safest simplest way to go as a 12 to 24v converter to handle the peak current is big and potentially a failure point.
good luck olewill

 

[vyv_cox]

My seawater cooled fridge uses a 12 volt pump running off 6 volts via a device made for the purpose by Isotherm. Something like this one http://www.isotherm-parts.com/index...d=1848&zenid=af27e319bbe02ff2acfb5f38304143b8 but less complex. It's one referred to on the page, where pressing a button gives an output of 12 volts. There is plenty of flow for fridge purposes, it makes the pump quieter and extends its life enormously.

Priming will not be a problem with a diaphragm pump, if that is the type the OP is talking about. It is a positive displacement pump, so the head and priming will be unaffected by lower motor speed but the flow will be reduced. My fridge pump primes a metre above the water supply with no problem.

 

[Tim Good]

Priming will not be a problem with a diaphragm pump, if that is the type the OP is talking about. It is a positive displacement pump, so the head and priming will be unaffected by lower motor speed but the flow will be reduced. My fridge pump primes a metre above the water supply with no problem.

No it's one with a simple impeller.

 

[Tim Good]

Simplest solution is to buy the correct voltage pump and stick the 24v one on eBay to recover some of your losses.

Any advice on the type? The one at the moment, if working correctly says it can do 50l per minute. That is a lot I feel for just a grey tank. The tank itself is approx 250l I think.

Would be nice to get one that would actually stop automatically when empty also as the current one just runs dry and you have to remember to turn it off.

This for example is half the price of my current one with in built pressure:

http://www.marinescene.co.uk/product/1528/jabsco-par-max-3-(12-volt)-pressurised-water-system-pump

 

[nigelmercier]

Simplest solution is to buy the correct voltage pump and stick the 24v one on eBay to recover some of your losses.

Agree, I've got a 12V pump that I replaced after one season as I wanted a bit more pressure. Going on eBay or For Sale forum when I get round to it ...

 

[jon711]

When running a 24V flexible impeller pump on 12V the amps will have a huge spike on start up... Best bet to change the motor for a 12V version (12V & 24V or interchangable).

Jon

 

[David2452]

Any advice on the type? The one at the moment, if working correctly says it can do 50l per minute. That is a lot I feel for just a grey tank. The tank itself is approx 250l I think.

For a grey water tank you can do a lot worse than a Whale Gulper, not massively high discharge rate but reliable and will pass a good amount of stuff like sink waste containing food scraps, soap scum from the shower etc. They are my weapon of choice for live aboard customers most of whom swear by them.

 

[Tim Good]

They are my weapon of choice for live aboard customers most of whom swear by them.

And your company is? Website?

 

[David2452]

And your company is?

As per my signature

Website?

That's the last thing I need, encouraging even more people asking me to do stuff.

 

[Tim Good]

As per my signature

Arr ok that looks more like a description.. i.e. a dealer of Marine Heating & Electronics on the East Coast. I see it now.

 

[john_q]

A lot less than 1/2 power probably

Apologies for the thread drift but if anyone has a water cooled Isotherm fridge and the voltage reducer for the 12 volt water pump goes down, fitting a 24 Volt pump is an alternative solution to paying Isotherm robbery prices for a new voltage reducer

Damn Vyv Cox beat me to it!!!

 

[Bodach na mara]

No it's one with a simple impeller.

You refer to the pump as not being able to "suck up water" to prime. Impeller pumps are poor at sucking up and require a positive head on the suction side, ie they need to be mounted at a level lower than the surface of the level in the tank from which they are pumping.

 

[Tim Good]

You refer to the pump as not being able to "suck up water" to prime. Impeller pumps are poor at sucking up and require a positive head on the suction side, ie they need to be mounted at a level lower than the surface of the level in the tank from which they are pumping.

Well that explains a lot then. 24v impeller pump in a 12v system rigged 1m above the top of the tank.

So this Whale Gulper 320 look good and half the price of my current Jabsco:

http://www.mailspeedmarine.com/bilge-saltwater-shower-pumps/whale/gulper-320-waste-pump.bhtml

 

[jon711]

You refer to the pump as not being able to "suck up water" to prime. Impeller pumps are poor at sucking up and require a positive head on the suction side, ie they need to be mounted at a level lower than the surface of the level in the tank from which they are pumping.

Sorry that's rubbish.... That pump will self prime from 6 feet....

Jon

 

[ccscott49]

For a grey water tank you can do a lot worse than a Whale Gulper, not massively high discharge rate but reliable and will pass a good amount of stuff like sink waste containing food scraps, soap scum from the shower etc. They are my weapon of choice for live aboard customers most of whom swear by them.

+1, Liveaboard, have four whale gulpers onboard, swear by them, great pumps.

 

[vyv_cox]

Sorry that's rubbish.... That pump will self prime from 6 feet....

Jon

+1. I used to run my engine ashore with the coolant supply from a bucket under the boat. About six feet up to the pump.