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Lowering Pump Speed with Low-Noise Fan Adapter?

post #1 of 7
Thread Starter 
So I have the Koolance PMP-400 (Laing DDC 3.25) pump without PWM, just a single 3-pin molex power connector. And Im wondering if it would be possible to safely lower the speed of the pump using a low-noise fan adapter? The one from Noctua lowers a fan to 7 watts according to their website. I hate the idea of buying a 50 dollar fan controller just to lower the speed of one pump one time for permanent operation at that speed. Also, if the low-noise adapter successfully lowered the wattage of the pump- that would also lower the total amperage the pump pulls correct? Potentially lowering it to below 1 AMP so I could power the pump off a 1 AMP motherboard fan header? Thanks for any help!
post #2 of 7
Low noise adapters work by reducing voltage, most of them are either 5v or 7v, but there are finer granularities available via resistors.

Current (amps) draw will remain the same, the reduction in wattage (volts * amps) comes from the reduction in voltage.

That Koolance pump has a starting voltage of 9V, which means that you do not want to use a LNA that delivers less than that, or you run the risk of the pump never turning on.

Edit: Also note that a LNA with a simple resistor won't lower total power consumption at all...the voltage reduction is achieved by wasting the difference...essentially converting the power to heat.
Edited by Blameless - 9/9/16 at 12:11pm
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post #3 of 7
The LNA might also burn up because that pump is surely pulling more power than the fans that noctua designed it for.
post #4 of 7
LNA is simply a resistor, nothing more. The important implication is that it only lowers the voltage to the desired level with the fan which resistance it is matched against. E.g. try Noctua LNA with Bitfenix fan - it will barely spin. Why? Because nominal current draw of Noctua fan is less than Bitfenix's.

Pump draws way more current than a fan, hence higher voltage drop on the LNA's resistor, hence lower voltage on the pump. Try that and you'll have mere 2 or 3 volts, give or take - so the pump won't run, or will run way too slow for practical use. It's not going to damage it though. LNA will heat more with pump but not by a whole lot since the current will be limited by its own resistance. Current will be less than without LNA because the total resistance will be higher.

TL;DR - Nothing should burn but it won't work as you intend it to either.
post #5 of 7
Well that's good. I was sure that the LNA would get hotter but I wasn't sure how much.

A pot operated voltage controller would probably be a better way for you to trim down that PMP to a more reasonable level without going to a fullblown 5.25 fan controller. Those are powerful pumps so you're going to have to look for a controller that can handle the wattage.

I used a lamptron FC1 to tune my heatsink fans when I was doing aircooling, it only supports 6W though. :/ Something similar that can operate at higher power is what you need.
post #6 of 7
Thread Starter 
Thanks for the help everyone. I misread the info on the LNA- lowering volts vs watts. I also don't know much about electrical engineering. But everything here now makes sense. I've seen fan controllers beefy enough for pumps but they're like 50 bucks (not worth it to me for lowering pump speed like 30% or something), and I cant really spare the room in my case. I'm now looking into modding the pump to be PWM or swapping out the circuit board to make it the slower/quieter variation of that pump that should pull less than 1 AMP.
post #7 of 7
Those fan adapters are just 1/2 watt resistors (with whatever value), pump is going to pull a lot more current and probably cause them to get very hot...

You need current regulation


here like $5

http://www.ebay.com.au/itm/DC-DC-Adjustable-CC-CV-Constant-Voltage-Current-Power-Regulator-Module-Indicator-/251636436207?hash=item3a96b34cef:g:Z5sAAOSwPe1UCDhJ

You'll need a multimter.

Basically:

12v into the module

Use MM to set output voltage to 12v

plug in pump, into output of regulator module, change current output to whatever you like (ie: turn it down to slow pump)

your pump apparently pulls 1.6 amps max
Edited by Slot1Gamer - 9/22/16 at 1:00am
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