AC Variable Speed Sump Pump + Sump Flow Calculations

[coreytrv]

Wondering if anyone has a good recommendation for an A/C variable speed pump to be used for a sump pump return. Can be external or submersible.

I say AC (over DC) because of head pressure. I have about 12' of head, and don't know how much flow will work within my system.

Starting with a couple data points from the forums:

Reefers here seem to recommend 3x - 5x total volume through the sump.
400DT + 20 (operating level of 40 gallon protein skimmer / dosing Sump 1) + 95 (operating level of 125 gallon refugium) = 1545 - 2575 gph / 25-43gpm

Tank is a 72" tall x 43" x 44" tank.
That means approximately 5.7 gallons per inch of DT volume.

5.7 gallons / inch x 2" = 11.4 gallons
@ 25gpm = Top 2" of the tank being turned over the overflow ever 30 seconds
@ 43gpm = Top 2" of the tank being turned over the overflow ever 16 seconds

That might be way too much, but I have no frame of reference. Plus feedings likely necessitate dialing back the flow.

What do you think I should consider for the primary sump pump return?
I have an MRC-MP 6100 which is 74gpm @ 12' head, which seems like way too much
I have a ReefOctopus Varios10 (DC pump) which is about 33gpm at 100% speed

One line drawing of the setup. Also keep in mind, the sump is secondary to a closed loop bead filter.
Photo of tank from top down:

 

[Snoopy 67]

Controllable speed pumps are DC ONLY. Refugiums need slower flow.
Abyzz is about your only DC choice here.
I get 43x44x72 divided by 231= 589.7 gallons for the tank.

 

[Stephensx04]

Jeabo dc20000 pump here. dead silent and has been bulletproof for few years now. pump from basement to first floor. 10+ vertical and about 17ft horizontal run to make back to tank. Pump only running at 60% and only draws 90 watts.

 

[coreytrv]

Controllable speed pumps are DC ONLY. Refugiums need slower flow.
Abyzz is about your only DC choice here.
I get 43x44x72 divided by 231= 589.7 gallons for the tank.

Abyzz are beautiful pumps! Very cool.

Also, thank you for running the calculation. The difference, I used outside dimensions, the acrylic is 1.5" thick which has a substantial effect on actual volume.

DC however are NOT the only options for controllable speed pumps. There are a variety of variable speed AC pumps. Think of your pool pump, or in my case, the Sparus Aquaculture Pump:

See below, you can see the pump curve / flow for various speed settings.

 

[14 foot reef]

There are AC variable speed pumps.

I will send you some examples in a bit. I believe Hayward is where you want to start you inquiry if memory serves me correctly

 

[Snoopy 67]

I stand corrected.
They say you learn something new each day.
Today was mine.

 

[BeanAnimal]

There are AC variable speed pumps.

I will send you some examples in a bit. I believe Hayward is where you want to start you inquiry if memory serves me correctly

In general a variable speed AC motor (brushless) will be three phase. The issue (other than expense) is that they lose torque as you lower the speed. Better VFD controls can do some fancy phase angle adjustments to help, but the drives become much more expensive. So add single to three phase conversion and the control logic to keep torque up and noise and heat down gets very expensive. Heat is also an issue. The VFD controlled motor is going to run hotter.

I retrofitted my drill press to a 3-phase VFD controlled motor. The first VFD was cheap China (maybe $200) and it was trash. It burned up. Teco (Westinghouse) makes decent drives for smaller motors.

Single phase VFDs exist - but there are numerous drawbacks and that is why you don't see them used at the sizes this hobby would need.