Buying new pump need help with head calculations

[SuperD]

Hello and thanks for viewing my post.

When I bought my house I received no documentation with the pool pump other than it looks old and it is a 1 HP sears model 390262801. The pump died a month after I had solar heat panels installed on my roof. The solar installer thought my motor would be fine at 1 HP to run the panels so it may have just been old and the extra stress killed it or some other coincidence. I'm using this as an excuse to upgrade to a new energy efficient model pump. I've been doing a lot of reading and research online, but I am having some trouble estimating my head so I know what size pump to buy.

I was eyeing the Pentair Whisperflo models as they are advertised to be energy efficient and quiet (anyone with more experience feel free to correct me and recommend something else). I'm just not sure what HP rating to go with since I'm not certain of the head in my system.

Here are my details:

• My piping to the pump and filter is 1.5" and the piping from my filter outlet to the roof and my solar panels is 2".
• My solar panels (Helicol HC-40) have a recommended flow rate of 4 GPM. There are 8 of them so I need 32 GPM through the panels.
• My filter, 100 sq ft cartridge, has a max pressure of 50psi
• With the water going to the solar collectors the pressure at the filter is about 12psi
• There is about 12' of vertical 2" pipe to the solar collectors on the roof
• The solar collectors are split into two banks
• I also run a barracuda G4 attached to my skimmer pretty much at all times

I have maybe 35' of 2" pipe on the roof for the solar collectors and maybe 47' of 1.5" tubing when I account for all the plumbing from the skimmer to the pump and pool jets.

From the tech graph I saw on poolplaza if I get the 1HP full rated version of the WhisperFlo I'd be ok as long as my head is not greater than 85. Anywhere between 85 and 80 seems to be where I need to be to send 32 gpm though the solar collectors if my understanding is correct. I don't think my panels will encounter operating issues until about 60gpm, but I also don't think it is good to exceed 42gpm in 1.5" pipe right?

[Me...]

The head will rise a lot trying to pump water up to the panels, but once it is flowing the water falling out them will help draw water up into them and the head will fall off again. So you really only need the extra "ooomph" to get water up to the panels.

You are right in trying to stay at about 42gpm with 1.5" plumbing but the filter will be no problem. Whisperflows are great pumps and a 1hp will do what you need although I think a 3/4 hp will be adequate. A 1/2hp will do the flow you need nicely but might struggle starting the panel flow.

[SuperD]

Edited..I'm going to try out the WFE-4. Thanks!