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View Full Version : Choosing the Correct External Pump Size


Red_Six
04/05/2006, 12:04 AM
I plan to add a 1/10 Arctica Titanium Chiller to my 58 gallon reef tank. I am wondering what size pump is adequate to achieve the desired 240 gph minimum to 960 gph maximum flow rate for the chiller. The suction side of the pump will draw from my sump. It will have four 90 degree elbows before it reaches the pump with about an eight foot horizontal run of 3/4" pipe. The discharge will also be 3/4" and it will feed the chiller and then return to the top of the tank. The return line will contain four 90 degree elbows, 10' of horizontal run and 4' of vertical lift. The chiller itself will add two 90's. I would desire the flow to be towards the lower end of the chillers range as I already have adequate flow in the tank. I figured on using all 3/4" fittings and pipe but there again I am unsure if that is the best choice. I thought perhaps a Mag Drive 950 would be adequate, but I am concerned that the actual head loss with all of those elbows would add up to greater than 11' of total head. At 11' the Mag 950 puts out 300 gph.

I have tried to calculate the head loss and came up with 17' :eek: I find this number hard to believe, and since I would rather have the flow closer to 300 gph than 900 gph, I don't want to make the mistake of getting to much pump.

Robert

Nabber86
04/05/2006, 11:50 AM
I figure you will have about 10 feet of head loss from:

http://www.reefcentral.com/calc/hlc.php

Does the chiller itself restrict flow that would cause additional head loose (might want to check with the manufacturer)?

Anyway, get your best estimate of head loss and then size your pump accordingly. It is almost always better to oversize a pump than undersize it (within reason, that is) so I would add a safety factor of 20 to 30 percent to the estimated head.

If you get too much flow - put a tee in the line downstream of the chiller. Then run the tee back to your sump through a gate valve. Adjust (open) the gate valve and divert flow to your sump until you get the flow that you want going to the display tank. This way you can let the pump run wide open without restriction.

OR You could just put a valve in the discharge line without the tee, but you dont want to create backpressure in the pump if you can help it.