by GroggyAl » Wed Dec 30, 2015 4:20 pm
I did a bit more work on my proposed self contained water cooling / recirculation system today. I have to give the 12v pump and tank that I used for my first couple of runs back to my son one day so I need to find a replacement. The 12v PD pump I think was perfectly sized (4.6 litres per minute at 60psi) however I would prefer 240v. It would just make for a neater installation with a single power supply.
I found a small plastic tank that will fit inside the old AC outdoor unit where the original compressor was mounted. It has a ball cock to maintain water level and a lid to keep sealed. Also from the scrap pile I found a 30w washing machine pump that could be mounted in the cabinet. After testing the pump today I don't feel confident that it will do the job. It can pump 8L/minute to 1.5m static head (open pipe) but by the time I run it through the radiator, RC and connecting pipe work it is down to 2 L/M with the extra friction losses. Despite having a NPSH of over 1.m it would not self prime without lowering the hose below suction head level. My cooling system will be mounted on the back wall of my shed so I can always raise it off the ground to overcome some head losses but my preference is to mount at ground level. Whilst it may be OK for my little Boka I don't want to rely on it for a new 4" bubbler in the future.
A 350w submersible pump from Bunnings will only just fit in my little tank but it seems a real overkill. I could not find a pump curve for the ozito but I found a simple head/flow curve for the similar 350w Commercial Electric barrel pump. The CE pump has twice the head but half the flow rate of the Ozito which may be better. There is no system or power curves to be found (if you could believe them anyway) but the specifications nominate a very low NPSH requirement in manual mode which should be ok in my small tank.
So this is where I need your help - has anyone measured how much current their 350w (1/2 HP) pump motor draws when throttled right back to very low flow rates? Being a centrifugal pump it should be lowest when throttled back (high pressure, low flow).
What is the minimum flow rate required for say a 4" bubbler RC.
For those using pond pumps, how does the flow of my washing machine pump compare (open flow)?
Any other recommendations / comments for a pump around 100 -150 watts (Submersible or dry mount)? My preference is the hardware store variety where I can rely on a warranty rather than go down the eBay route. I guess my fall back position is the 12v PD pump.
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