Fan Speed Controller for Return Pump Control?

I'm working on building my 90 Gallon cube and I've come to the return pump research point. I'm interested in something over 1200 GPH. But I'd like to be able to reduce the flow by controlling voltage rather than a restrictive valve or bleed off system. My though behind this being that I'd rather save on the electricity that waste it and have it go straight back into the sump. Also, I'd like to turn the pump down significantly during feeding.

I've used Fan Speed Controllers lots before to control ventilation systems but is it safe to use these devices with pumps? The idea with ventilation fans is that having an oversized fan running at half throttle is more efficient and reliable than a smaller fan at full throttle.

Anyone have any insight to offer?

Edit: I've got a call in to Pan World to see what they have to say.

 

Not sure on yours, but on my Coralife & Iwaki pump it will not. It's a mag driven impeller. Which mean, if the motor does not get up to it's normal speed, it will not engage the impeller or not run it correctly.

I know on the Iwaki Hybrid it will use less wattage, if it senses the flow being cut back with a valve after the pump.

 

You can't use a speed controller or dimmer with most normal pumps. They (Hydor, Tunze off the top of my head) sell special ones meant for controllers.

 

That's an interesting question, Broaner. Motors are rated for voltages of 120 or 240, nominal--not including those used in industry. Controller compatible models of which blackraven speaks, utilize circuit boards for ramping up/down the power delivered, but they're still operating at 120V, and they're smaller, in-tank water movers rather than motor driven pumps.

If an inductive electrical device such as a motor is deprived of voltage, it will consume exponentially more amperage to achieve its rated output--while producing far more heat and the potential for fire.

I think the best you can do is to complete your research, find out how many GPH you'll require (taking head loss into account), and spend a bit more on an efficient motor which will use less amperage over the long run.

My first pump was a Little Giant 2MDSC. It took 1.65 amperes to spin at 3000 RPM and moved 435 GPH at 4'. Not terribly efficient compared to the Iwaki MD40RLXT I use now. It takes the same 120V and at 3200 RPM, moves 750 GPH at 4', while consuming 1.3 amps.

If you have the money, Red Dragon pumps are some of the most efficient pumps available. For example the RD 8.2 Deluxe will move 2165 GPH consuming a mere .625 amps! It's yours for the princely sum of $800 or so. Too rich for my blood. :-/

As with most devices, we seek the variable that's most important--like power consumption, flow rate, noise, etc.--and go from there.

Good luck in your search. Keep doing your homework, and ask plenty of questions. You're bound to be happy in the end.

 

Thanks for the input guys.

Just found my answer from a manufacturer. Apparently an AC motor needs to be 3 phase to be "dimmable" Cheapest 3 phase on the Market seems to be the Kingfish 750. Retails $1250 and at 20% throttle runs 2000 GPH at 0 head so... A bit excessive for my 90 gallon needs to say the least.

 

One question...how were you planning on running a 3-phase motor, if say it had been inexpensive?

 

The input voltage is Single phase 120 and it takes care of itself from there apparently. Thats what the rep said. I thought that was a bit fishy but I'm certainly not an electrician.

 

I am.

 

This is interesting, Do you have some insight on what would be required to run a 3 phase motor? Just out of curiousity.

 

3 phase AC power.