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Need assistance with pump selection.

Need assistance with pump selection.

Need assistance with pump selection.

(OP)
I have a buddy that is attempting to....and I quote.
"I need a 110v pump that can pump water from 60+ feet down
The use: I am going to use an old "A" coil and fan housing and tie it into my central heat and air cold air return on the boat. The deep water temp on my lake is pretty cold so I want to make my own geothermal AC unit. Any suggestions appreciated. I think."

My comments are as follows.

1.Correct me if I am wrong but you would only have a couple of feet of head pressure as the water level would equalize on it's own.

2.Only other thing you would have to worry about would be friction loss but it would be minimal at 60 ft.

His comments are as follows.

1.I thought that too swifty but you are lifting the weight of all the water in the tube the entire length of the tube because it is enclosed. The head will only be 2 feet at the most, but the suction will be 60 feet plus. If you look at pump specs you can see how the gpm reduces as the depth increases until you get to zero.


Bottom line I'm curious as to who is correct. I like learning new things.Pat


 

RE: Need assistance with pump selection.

if i understand the concept correctly . . .

the pump would need to be installed at the source of cool water . . . trying to "lift" or pump water 60-feet below the pump will not work - think about the fluid vapor pressure of the water trying to "lift" it 60-feet.  tell your friend to save his funds and abandon the idea . . .

-pmover

RE: Need assistance with pump selection.

(OP)
He is planning to sink his pickup line/suction line to 60 ft deep of the side of his House boat.  

RE: Need assistance with pump selection.

(OP)
Which is about 2 foot above water level. Needed info.

RE: Need assistance with pump selection.

I don't see any initial problems.

When the tube is hung over the side to 60 ft depth (BTW he may only need to drop to 25 feet; the first thermocline is often at around 20 ft) the water will rise on its own to lake surface level.  Then you really only need to "lift" the (2 ft?) distance from lake surface to the pump centerline.  As the pump is started and flow begins, friction and head loss in the tube increases (thereby increasing the effective lift distance), but, if frictional loss is limited by a proper diameter selection, and the distance from water surface to pump centerline is minimal, you should be able to stay within the NPSHR for a properly chosen pump.  Certainly a 2 ft lift, given an additonal small friction head loss in the tube is possible, even for a self priming pump.  You will need to add power for any additional head loss for the deck piping and for the head loss in the heat exchanging coil before dumping overboard. (I'm not sure if that's exactly legal or not, even though you think you really didn't process the water in any manner; zero discharge is ZERO disharge, so check the lake regulations).  If a self-priming pump NPSHR is still too high, alternatively, you could always try a small submersible pump, dropped to 25 ft, and essentially avoid any NPSHR problems entirely.  

Now whether the pump's flowrate and power will be sufficient to give the cool water flowrate needed for cooling the hot air in the cabin may be another story, but that's just a question of having enough available power on the boat to run the pump and any other appliances you want to run all at the same time.

"The top of the organisation doesn't listen sufficiently to what the bottom is saying."  Tony Hayward X-CEO BP
"Being GREEN isn't easy." Kermitfrog http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com

RE: Need assistance with pump selection.

Swifty,

Lefty your buddy isn't right of course, but if it had turned out that he was, 34 ft would have been your theorhetical max lift.  Check the steam tables.

Otherwise, BigINCH nailed it.

rmw

PS: BigInch, did you run with the bulls this year?

RE: Need assistance with pump selection.

(OP)
Thanks guy's with your help we have him on board with us now!

Also... Gonna save this forum to my Favs.
Pat

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