New pump and solar heating design

[Dr. Pipper]

I am in the SF Bay Area and have a 15k gallon in-ground pool with a 1HP pump and cartridge filter. I plan on replacing the pump and installing a solar heating system. I know that two speed pumps have a lower up-front cost, but the ability to tweak flow rates for the solar system makes a variable speed pump attractive. Would I be able to run through the solar panels on the slower speed of a two speed pump, or would I need to run at the higher speed? I am trying to determine what size pump I need and whether it makes more sense to go with a two speed pump or a variable speed pump. All of my plumbing is currently 1.5". I don't have any water features or automatic cleaners.

I have done much reading on this forum, h2otsun.com and elsewhere online and have come up with a schematic for my solar heater design. Does it matter which location I use for the vacuum relief valve? Is there any reason to put ball valves on the solar panel supply and return lines, since I can just bypass the solar system with the 3-way valve? Does it make a difference if I run 1.5" or 2" plumbing up to the roof? Am I missing anything else?

Thank you so much for the help. I knew nothing about pools when I bought this house 5 years ago and ended up with a green swamp, but thanks to this site I have a sparkling pool.

 

[mas985]

Welcome to the forum.

I am partial to that solar design as well. My preference is to put the VRV in the optional location in ther picture. That location has the benefit of allowing pressure to be lower at the pump than if you put the VRV at the back end of the panels. So, you will be able to run at a lower RPM with a VS pump.

In order to run on low speed of a two speed pump, the VRV has to be move all the way to the pad (~6' high). This can be done but not many controllers will allow a two speed pump to be run on low speed with solar engaged. Also, the pump will need to be run on high speed for a short time to prime the panels and then switch to low speed. The only real way to do this is with a a two speed timer and separate solar controller.

 

[JasonLion]

Welcome to TFP!

Larger pipes are better. They will increase the total flow rate, which improves both heating and electrical efficiency.

Unless your roof is unrealistically low a two speed pump running on low will not work with the solar panels. You will need to run it on high. A variable speed pump will be able to run somewhere around 3/4 and work with the panels while using less electricity than a single speed on high. However the savings will be small and will take a long time to pay back your investment. Since you are in CA with high electric rates, it might still be worth getting the variable speed, but it is nowhere near as dramatic a savings as running without the solar panels would be. On the other hand the electric costs to run the pump are not even remotely close to the much higher cost of running a gas heater to get the same heat, so solar is still the way to go.

I would put the vacuum relief valve on the far end of the lower header, but it will also work where you have drawn it.

 

[Dr. Pipper]

Thanks for the input Mark and Jason!

I have seen several designs that include ball valves on the solar supply and return lines (see attached drawing). What is the purpose of this? Can't you just bypass the solar system with the 3-way valve? Also, will I need to add drains to the solar system and if so, where? The coldest it will get here in winter is ~35F, so we get occasional frost but never a hard freeze.

 

[JasonLion]

The isolation valves are used when the solar panels are leaking or taken out of use for weeks at a time. They guarantee that the panels stay dry even if the check valve leaks or the diverter doesn't completely seal closed. It isn't especially likely that you will need them, but if you do need them it can be a real pain if they aren't already installed.

 

[Isaac-1]

Like Jason said the ball valves provide positive isolation, also the "solar" 3 way valves have a small pin hole check valve built into them to let the lines drain down on the cold line side these can leak and slowly fill the panels with water which can be a problem if exposed to freezing temperatures. In addition to the isolation valve you may also want to consider a manual drain valve and a if going with a 2 speed pump a bypass loop with a valve around the solar panels to allow fine tuning of bypassing excess flow if you don't get your pump size just right (like what you show for your heater).

Ike

p.s. 2 inch pipe may have some advantage going to the panels depending on how many you install, I used 2 inch for my recent solar upgrade, my rough math show the benefit to using 2 inch from the pad to the roof with 1.5 inch in ground pipe shows the advantage really starts to show up with over about 8 4x12 panels assuming typical number of fittings.

 

[drdjsmm]

I'm getting ready to pump water up to my roof to 2 - 4' x 20' solar panels.

1.) Do you need the two Vacuum Relief valves? Where do you buy them at?

2.) Where do you buy the isolation ball valves?

 

[Isaac-1]

You can get vacuum breakers at Lowes they also sell pvc ball valves but the lowes brand ones have a habit of getting stiff after time.

Ike

Sent from my GT-I9000 using Tapatalk 2

 

[Dr. Pipper]

I have continued my research and have come up with a tweaked design and shopping list:

Pump: Pentair IntelliFlo 011018
Panels: 6 ea. Fafco 4'x10'
Flow Meter: FlowVis
3-way: Jandy NeverLube
Plumbing: 2" for everything except pool return/suction lines

Possible future upgrade:
Automation: Pentair SolarTouch

At first I was considering a dual-speed pump. They seem to be about $300 less than the IntelliFlo, but I can get a $100 rebate on a VS pump and I really like the ability to fine tune flow for the solar. My electricity is $0.24/kwh so any reduction of energy consumption helps a lot.

I replaced the separate flow meter and check valve with a FlowVis in the solar return line. I assume that measuring flow in the solar return instead of the solar supply will provide the same information.

I really appreciate all of the help!

 

[Isaac-1]

My only concern might be that the combo check valve / flow meter might put more back pressure on the panels than a plain check valve.

Ike