What new pump do I need??

[JamesW]

If the system is sealed, then you get the head loss back.

However, solar is typically not sealed.

There is usually a vacuum breaker somewhere.

For example, if the water has to go up 30 feet and the vacuum breaker is at 20 feet, you get back 10 feet plus the dynamic head loss from the roof to the pool.

I would suggest the intelliflo pump with a solar controller that adjusts the flow when heating.

If you want a single speed pump, a 1.25 total hp WhisperFlo might be a good choice for you.

The WFE-3 (3/4 full rate) and the WFE-24 (1 hp up rated) WhisperFlo pumps are both 1.25 total hp. They're the same exact pump.

You typically want about 4 gpm per panel. So, at 12 panels, you would want about 48 gpm.

 

[mas985]

I disagree, solar plumbing typically IS sealed or there would be many complaints on the forum of air in the return lines when running solar. This does happen on occasion but if a system is designed properly and the VRV placed in the proper location, the VRV will remain closed during all stages of operation. When the VRV is closed, the plumbing is sealed since no air can get in or out of the plumbing. The system then behaves as if there were no VRV at all.

There are three distinct stages of solar operation:

Stage 1: When first turned on and the solar plumbing is empty of water, water will start to fill the supply line. During this stage, air will typically exit out of the VRV since most VRVs allow air to pass but not water. Once the water hits the VRV, the VRV will close due to excess water pressure (> 0 PSI). The head loss at this point is the sum of the dynamic head loss and static head loss to the point of the VRV only and possible to calculate.

Stage 2: Once the VRV is closed, the remaining part of the solar plumbing starts to fill with water and back pressure to the pump continues to increase as dynamic head increases in the remaining plumbing. Head loss during this stage is very difficult to determine since there is a mix of air and water and things are very chaotic and dynamic so it is nearly impossible to calculate head loss.

Stage 3: Once the the return pipe is completely filled with water and there is no more air in the solar plumbing, static head loss of the water rise and water fall net out to zero but again, only if the VRV remains closed. At this stage, head loss is much easier to calculate since it is just the dynamic head loss of the plumbing. The vertical rise of the pipe no longer plays a roll in the head loss calculation.

However, there can be situations where the pressure at the VRV drops below 0 PSI during the transition from stage 2 to 3. Air enters the VRV and the return pipe then drains or partially drains and the system reverts back to the start of stage 2 and the cycle starts all over again. This can cause oscillations between the stages and the panels never maintain prime. This will usually happen because the dynamic head loss in the post VRV plumbing is not sufficient to keep the VRV closed. Usually the solution to this is to either increase the return side head loss (via smaller returns) or to move the VRV closer to the pump to increase the pressure. Some installers will put the VRV at about 6 foot above the pump on the supply side to avoid any issues. Plus this will allow you to run on lower speeds of a VS pump while still maintaining full prime and keeping the VRV closed.

 

[JamesW]

If the panels are at 30 feet and the dynamic head loss from the panels to the pool is only 10 feet, then the panels will be under 20 feet or 8.7 psi of vacuum.

I don't think that the panels are rated for that much vacuum.

Not installing a proper vacuum relief valve, or installing it in the wrong position could result in collapsed plumbing or panel failures. A VRV should be installed at the highest point in the system whenever possible.

Vacuum Relief Valve for Solar Pool Heaters

Many vacuum relief valves are installed at the highest point. At this point, we don't know where the VRV is.

If you want to get back the head lost on the way up, the panels need to be under vacuum. It just depends on how much vacuum you want to put the panels under.

You can restrict the return to prevent or reduce vacuum in the panels, but that doesn't get the head loss back.

 

[mas985]

I have seen panels rated at +- 30 PSI. I have run mine at negative pressure before on low speed without issue so I know it can be done.

But for the OPs case, I think the pressure at the return side of the panels would be higher than -9 PSI. Given the setup I have seen so far, I estimate the head loss would be about 20' from the panel outlet to the pool and the pressure at the panel outlet about -4.3 PSI. At the inlet, where I would put the VRV, the pressure is about 1.2 PSI. Filter pressure would be around 15 PSI and the operating point would be 55 GPM @ 45' of head. But these numbers of course depend on the actual layout of the plumbing.

The alternative, is to get a much larger pump so that you can ensure you have positive pressure at all points in the plumbing. That means running a very large pump and using lots of electricity. A waste IMHO.

 

[JamesW]

Head loss of 20 feet from the outlet of the panels to the pool at 55 gpm would be about 400 feet of 2" pvc pipe.

How much head loss you get back depends on how much vacuum you're willing to put on the panels.

Also, the VRV doesn't necessarily need to be closed. If it opens, you will just get air in the lines. It's aeration, which can cause ph rise, but it can be done.

 

[mas985]

Head loss of 20 feet from the outlet of the panels to the pool at 55 gpm would be about 400 feet of 2" pvc pipe.

Here is the equivalent pipe length for each component I included:

Return Pipe on roof from far side of panels: 48'
Pipe down wall: 30'
8x90's for solar return to pad: 48'
Flapper Check valve: 33'
Tee: 11'
Pad Pipe: 3'
Heater: 132'
Pipe run to pool: 30'
5x90s for pad & run to pool: 30'
Eyeballs (4x3/4"): 44'

Total: 409'

 

[JamesW]

The Intelliflo would probably be the best choice because you can adjust it as needed.

 

[JawJa]

Update...

I have been talking to some local folks... did not realize one of my neighbors works for a local pool company (Sunbelt)...
Anyhow, I hear again and again... to use a booster pump for the solar, and size the main pump for without solar.

Now given that I have a SuperFlo 1HP (SF 1.65)... I may well rebuild that pump and use it for the booster.

I am kinda leaning towards using a WhispeFlo 1HP 2 speed for the main pump, with the T10604R timer to control the pumps...
The solar works best for about 3 hours when the sun is actually directly on the panels... before and after that... the sun is partially blocked from the panels.
My thinking (assuming I am understanding the way the T10604R works)...
Is to set up the 2 stage timer for a 9 hour run:
*Start with a short time on high, to get the pump primed and water flowing...
*Then down to low for 3 hours for filtration...
*Then up to high for 3 hours for the solar time... with the booser kicking in and the solar valves opening up...
*Then back down to low for 3 hurs with the booster off to complete filtration for the day.
Seems this way... I get the advantage of the low speed for filtering, and the booster to move the water up to the solar.

Thoughts???

I am kinda hesitant to invest $1200 in a high end pump... just a lot of $$$ at this point... and honestly; the idea of running the Intelliflo almost flat out for 3 hours seems like a good way to have that $1200 have a short life...

One question I do have:
From looking at performance charts...
It would appear that WhisperFlo pumps move more water at the same HP than SuperFlo pumps...
Am I reading the charts correctly, is this true?
The folks at InYopools agreed... but then they seem to agree with everything I say... almost as though they just want to sell me whatever I want to buy...

 

[mas985]

My thinking (assuming I am understanding the way the T10604R works)...
Is to set up the 2 stage timer for a 9 hour run:
*Start with a short time on high, to get the pump primed and water flowing...
*Then down to low for 3 hours for filtration...
*Then up to high for 3 hours for the solar time... with the booser kicking in and the solar valves opening up...
*Then back down to low for 3 hurs with the booster off to complete filtration for the day.
Seems this way... I get the advantage of the low speed for filtering, and the booster to move the water up to the solar.

Thoughts???

That is how the timer works but it won't necessarily be in-sync with solar unless you get a solar controller that can handle switching off the booster.

Also, running without the booster probably won't buy you much since you would be getting plenty of run time with solar.

One question I do have:
From looking at performance charts...
It would appear that WhisperFlo pumps move more water at the same HP than SuperFlo pumps...
Am I reading the charts correctly, is this true?

Yes, that is true. One reason you should never size pump by it's label HP. It can lead to the wrong conclusions.

BTW, the WhisperFlo on it's own could run the solar just fine and the panels would not be under negative pressure at all. But it does depend some on your actual plumbing layout which so far, you have yet to describe in detail. If you can give some more details about the setup (run lengths, eye ball sizes, valves, etc), I can tell which pump would work well and maintain positive pressure for the panels.

However, the nice thing about the Intelliflo is that there is no "sizing" required since it is variable. You can choose the minimum RPM to keep the VRV closed and maximize energy efficiency. You would likely pay off the extra cost of the pump in a short period of time because of this ability to optimize flow rates and energy efficiency.

 

[Semi-retired]

JawJa, I'm on my fourth pool and fully relate to the "new-to-pools" feeling/situation. I found this site many years ago (actually its predecessor I believe) when on my first pool in Illinois. The site has been a godsend for so many issues: plumbing, sizing, chemistry control, chemistry problem correction, problem diagnosis, other pool owner experiences, I could go on for a page. Of the many things that I have learned, for me at least, is that the four best investments (besides the pool) are a VS pump, SWCG, automation, and solar pool heat. Besides the TFP approach to maintaining pool chemistry balance, for me, these equipment features increase the ease and enjoyment of pool ownership a lot. I had none of these, or only one or two, in my previous pools. Since I built (had built) this pool I decided to go all-in. I have solar on the roof at about 30', two water falls (yep, water features really do drive pH), and the SWCG. The VS pump along with automation makes running these different flow needs a snap. To keep the pool circulating and filtering, I run the VS at very slow speed 16+ hours a day for literally pennies, easy. Ramp up VS speed for the water features at certain usual pool use times, easy. Automate solar heating with a VS speed ramp up to get the water up to the peak and ensure VRV seats, easy. Set the SWCG at a level that supports the time of year and pool usage to ensure a level concentration of free chlorine, easy. Have the pool lights come on at night (or just weekends) and turn off, easy. All of these certainly cost a lot, but for me the benefit has been great. After using this pool for 4 years, I actually asked my wife which of these we could do without if/when they fail...she said none. I said, "even if that means we don't eat out for a year to pay", she said "yep". I take that with a large grain of salt, but....