Originally Posted by winstonofbeer
Looking at pumps for this project,
Whats the gph that works best for this project?
I am finding 40 - 130 gph depending on the pump for all around 20 bucks.
Slowly starting to get this project on the move.
Originally Posted by 944play
I will suggest as small
a pump as you can find that will move the water. Two reasons:
1) The pump itself creates heat. That 258GPH uses 20Watts which all gets turned into heat. That is ~ 68 BTUs. If the pump runs 50% of the time (I don't know what's typical with these systems), that's 68 BTU x 12 hrs/day = 816 BTUs. A pound of ice absorbs ~ 144 BTUs melting, so 816/144 = 5.6#, so that's almost 3 Quarts ice melted by the pump
each day. Almost six quarts/day if it running full time to initially bring temps down, less if the pump runs much less though.
2) I'd guess there's only ~ 3 gallons chill water in the cooler with the fermentor? So a +200GPH pump will replace that water in less than one minute. OK, some blending of the water, but in only a couple minutes the water near the fermentor has mostly been replaced with the cold water from the ice cooler. But it will take longer than that for the fermentor to actually change temperature. In the mean time, you are just running the pump for no reason - the water is not getting any colder.
A 5W pump will push maybe 30GPH through the hose, .5 G/minute, so it would take 6 minutes to do one changeover (which will have a blend of water in reality). This gives time for the fermentor/thermostat to react, yet it would seem to provide plenty of cold water in that time.
So a small pump will generate less heat, and might even give more stable temperature by slowly cooling the water bath, giving time for the thermostat to respond.
Check out some of these:http://www.jebao.com/english/products.php?current=2&laywer1=4774
Watch the 'max head' - .5 Meters in some cases, you need to keep the max lift of the water to less than 'max head'.