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After review the data sheet for this pump the one characteristic that is missing is the max pump head heigth. I want to use this with my parabolic collect that needs a minimum of 6 ft. pumping heigth. Will the pump work. If not, how about the 24 volt version?

If i am looking at the right pump (EWP-D50C124030L), it actually does specify the "max pump head height". Measuring in feet of water and measuring as a matter of pounds per square inch is the same thing only in different units. The spec sheet says its shut off head is 6 psi--this would be gauge pressure which is that above atmospheric pressure.

Converting between feet and psi is a rather simple conversion to do in your head. Atmospheric pressure (psia, pounds per square inch absolute, -- also just a reminder that this is at sea level) will 'lift' a column of water almost 30 feet (or mercury about 30 inches) and measure almost 15 pounds per square inch absolute (which would read 0 psig or psi gauge0. Thus, for close enough sort of estimates, one psi (gauge which again is above absolute) = 2 feet of water. (You can buy a pressure gauge that will read inches or feet of water instead of psi.) That means this pumps shut off head, assuming the 6 psi is correct, will be in the neighborhood of 12 feet. To test it you can do one of two things with a simple test system":

Run a tape measure up the side of your house or a tree up to say 15 feet along side a piece of clear typgon tubing or else put a pressure gauge in the neighborhood of 0-10 psi range on the discharge side of the pump with a shut of valve or attach a garden hose you can kink for a moment. Obviously give the pump a source of water to its suction preferably with a little height to it (above pump suction). Turn it on and see how high it pumps. If you go the gauge and valve or garden hose discharge route--shut off discharge flow just for a moment and see what shut off head reads on your gauge. In general, don't run long at shut off head as things will overheat but no need to be neurotic about it -- that goes for your hose up the tree method also as no flow is passing through the pump unless it is spraying out the top of your hose which would mean you are really in fat city.

Going to the 24 volt model will not get you more in the terms of shut off head--that has to do with the pump (slippage)--at shut off head the pump is churning as all its discharge which is 'slipping' from the discharge side back to the suction side which also causes the water to heat from the work that the pump is doing. More likely also due to counter EMF and shunt winding design, the only advantage of going to 24 volt is to draw a little less than 1/2 the current the 12 volt model does--that's the usual case. (Below shut off head, it generally is the case that varying voltage will vary the pump output but it depends on the windings of the motor--most are shunt which means that the voltage supply is not necessarily controlling speed but most do but within the ability of what it is connected to as in the pump and almost all shunt motors incorporate a speed limiting circuit to protect the motor. It really is not a good idea to speed control most pumps--they should be operated at BEP (best efficient performance) and flow adjusted otherwise given the pump is properly sized. From a practical perspective--the power the motor consumes will be determined by the load (pump)--its the same pump either way--you can do it 12 v and say for example 2 amps or 24 v and 1 amp--what the amps will be exactly i couldn't say--but can say the relationship holds.)

If you need more head--you need a pump (pump end) designed to produce that. They list a high head pump you could look at which is perhaps designed with applications like yours in mind. Centrifugal pumps are high volume, low pressure pumps but 6 feet of head isn't very much.

Now i am not quite clear on the specs of your parabolic collector. From the sound of it, it requires a about 3 psi at the collector which means to be safe that this pump should be mounted no more than a couple feet below the collector--technically within 6'+6 feet for the collector but it would seem but that would be stretching it and performance would at least suffer. That is, what you need is a pump that can supply whatever the height of the column of water would be to the collector plus 6 feet to overcome head loss within the collector itself and then some to put the pump in its actual performance region and to account for other head losses.

Our little 12-24 vdc pump in our computer water cooling system puts out about 4 psi or 8 feet (9 is shut off head--which you never really operate at successfully). The 240 vac pump in our geothermal system which circulates water through 3 200 feet wells and supply to and from the house and through the heat pump hardly puts out more volume but does put out more head as it is essentially a vane positive displacement pump.

Hope that helps.