Determining panel size to run shurflow pump

Aug 10, 2015 04:51 pm
Determining panel size to run shurflow pump

MY PLANNED APPLICATION:  I want to power a SHURFLOW 12V, 3 GPM, DIAPHRAGM WATER PUMP  [#2088-343-435] directly from a PV panel (don't want to have battery involved).  The pump will fill a 20 gal holding tank; tank only needs refill about once/week.    I would only run the pump during afternoon sun.

QUESTIONS:  What's the smallest size panel I can get away with for this use?  Would I need a charge controller?  The pump's max voltage allowed is 13.6.  The pump is 7 amps.

Thanks for your reply.
462 Posts
Aug 24, 2015 12:54 pm
Re: Determining panel size to run shurflow pump

Douglas, did you already purchase the pump? If you only need 20 gal / week and that pump does 3gpm then only 7 min of run time. I would think you could get away with a much smaller pump that could run directly off a small PV panel. Wire it to a float switch on your tank. Then it should be able to maintain the level throughout the week.
  What type of head do you have between the water source and the tank? This will drive the model pump you would need.  A small submersible may be all you need. Look at marine or boat supplies or your local hardware store.
« Last Edit: Aug 25, 2015 10:53 am by Tom Mayrand »
Sep 3, 2015 06:35 pm
Re: Determining panel size to run shurflow pump

The reason I was specifying that size pump is that's what I've always used at this cabin (and I have an extra one of that capacity), but now I'm building an elevated holding tank at a different location on the property and this holding tank will just serve a sleeping cabin with limited water needs.  The sleeping cabin is about  70 feet from the water level and will be about 20 feet above the water level.  I don't want to have a float switch involved because that will require an electrical line from the holding tank to the pump (i.e., 70+ feet).  The pump has to be very close to the water level because that's how these style of pumps operate best.  They can't "pull" water  very high, but can "push" water a long ways and up quite high (my current pump that supplies water to the cabin is about 1 foot from the water; the cabin is about 60 feet from the water and about 20 feet above the water level).  So for the pump serving the new holding tank, I just want a small panel wired directly to the pump.  Don't want a battery involved because batteries require maintenance.
462 Posts
Sep 4, 2015 12:30 am
Re: Determining panel size to run shurflow pump

Well, simply 7 amps x 12 volts =84 Watts, so any panel above this should work.
47 Posts
Sep 14, 2015 09:53 am
Re: Determining panel size to run shurflow pump

You need to determine the dynamic head, which is the total height including the friction loss for the 70' across, in addition to the static head, which is the 20' up you are going. Assuming 1/2" pipe at 2GPM, that's 3.5' for every 100'. So let's say 3' + the 20' static = 23' head.

The ShurFlo is rated in PSI, not head, so searching online for a foot of head to PSI calculator, I see you have to achieve 10PSI.The amps for that pump at 10PSI is 5.3A. Now granted, you will likely need more than that to get it started, but since you need so little water, you don't need to get it running first thing in the morning, so you can wait until midday for the pump to start. I'd probably go with a 100W panel, to ensure that it does have enough current to get the panel started. It has a Max Power Amperage (Imp) of 5.56A.

If you are not using a float switch, what is your plan to control water flow?Will you just have it overflow? Is there something you can think of to do with the extra water? I hate to waste.

Solar Queen
altE Store

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