PSU / pump not working to spec.

[the_ether]

I'm experimenting with a water pump. Its specs say that it can pump water up a 3m height but I only get around 0.5m.

The pump's specs are: 12V, 1.8A
The PSU's specs are: 12V, 2.5A, 60VA

The PSU is a standard brick of the type that is used for laptops.

This is the pump: https://www.sparkfun.com/products/10455

I measured the voltage at 12.3V but the current was only 0.33A

I measured the pump's resistance to be 2 Ohms but presumably as soon as it starts spinning the inductance will cause the motor to have a higher resistance.

Even though the PSU is rated for up to 2.5A, why do I only see 0.33A?

Should I simply buy a new PSU but with 6x the current rating?

[corrado33]

It could be that the laptop power brick has circuitry that prevents it from working if it doesn't detect the correct thing on the other end.

Try it with a real power source (or a simple car battery) and report back.

[the_ether]

It's not a laptop PSU. It is simply similar to one. There is nothing in the specs to suggest that it is designed for a specific device:

http://cpc.farnell.com/ideal-power/25hk-ab-120a250-d5-fr/psu-desktop-12v-2-5a-3-pin-iec/dp/PW03344?Ntt=PW03344

And it is working, it is simply only outputting 0.33A. My guess is that it's something to do with the inductance of the load.

I have no other power source to verify whether it is the pump or not.

[Psi]

Could also be that they shipped a 24v version by accident.
Or installed 24v motor in 12v model etc..
If it doesnt draw the current its supposed to, and pump the water quantity, when using a proper power source then i might suspect that

A car batt ,with engine not running, is a easy source of 12v.
Just dont slip and short it, they have crazy current available

[rob77]

It's not a laptop PSU. It is simply similar to one. There is nothing in the specs to suggest that it is designed for a specific device:

http://cpc.farnell.com/ideal-power/25hk-ab-120a250-d5-fr/psu-desktop-12v-2-5a-3-pin-iec/dp/PW03344?Ntt=PW03344

And it is working, it is simply only outputting 0.33A. My guess is that it's something to do with the inductance of the load.

I have no other power source to verify whether it is the pump or not.

if you measured that 0.33A , with the pump, then it's the pump drawing only 0.33A , not the supply outputting only 0.33A
go ahead testing with a 12V battery as suggested above. furthermore you could test the supply by attaching a 10R power resistor to it's output (without the pump connected)- you should measure approx 1.2A.

[Circuitous]

By 0.5m is that the lift height you're getting?   Lifting is the intake side of the pump.  I would think that it should be able to pump water to a few meters high, but the lift height wouldn't be anything like that.

[the_ether]

By 0.5m is that the lift height you're getting?   Lifting is the intake side of the pump.  I would think that it should be able to pump water to a few meters high, but the lift height wouldn't be anything like that.

I don't see why the lift should be different from the head. The two together should be the max capability of the pump. The pump is rated for a head of 3m ie the lift plus head should be < 3m.

At any rate, the lift was zero. This is a bilge pump. the intake is through its base and I tested it resting on the bottom of my bathtub.

And to answer the others, as I said, I have no other power source. This also means a 12V battery.

And testing the PSU with a passive resistor won't tell me much. The motor is inductive.

Thanks anyway. I think that I'll just buy a PSU with a higher power rating.

[AmmoJammo]

Where does it list the 3m height? I might be slow (its cold today!) but I can't see it?

[rob77]

read the comments on the page you posted - it's explained there in the very first comment
it's a centrifugal pump - high flow rate with minimal pressure

[tautech]

I don't see why the lift should be different from the head. The two together should be the max capability of the pump. The pump is rated for a head of 3m ie the lift plus head should be < 3m.

Sorry you are quite wrong, it is not that simple.
The suction lift of a pump has the greatest affect on it's capabilities.
The only way to expect rated specs is with a "flooded" suction lift.
That is with the pump below the point of suction.

[SeanB]

3m head means at ZERO flow the pump can generate 3m of static pressure on the outlet water column. With flow ( even just pointing the outlet up and seeing how far it goes up) you will have a loss of head, so 0.5m sounds about right.

If you want higher head go get a larger mains operated pond pump, as there you can get a 15m head one designed to operate fountains, which will easily operate a 3m high fountain at full flow.

[PE1RKI]

did you reverse the power leads ?