Online RPM calculator to maximize heat?

[eegz]

Situation
I've been reading threads on head on and off for a few years as I replaced parts of my system but I'm having a hard time putting it all together to figure out the best RPM to get the most heat out of my solar thermal panels.

Question
Is there an on-line calculator I can plug all my info into to get an RPM setting with/without solar?


Calculating head
I tried to calculate static head, but the tables I found top out at 2" and they requires the gpm which is what I'm trying to find so I can set my RPM.
On just the dips, turns and twists part I ended up with about 3200 feet of head which seems more than a bit off:
To Solar: approx 105' with 14 corners, 4 couplings, 6 45's, 1x 2-way ball valve (head: 10 + 14x 9.8 + 4x 2.5 + 6x 3.8 + .4 = 1459.6')
From Solar: approx 105' with 16 corners, 7 couplings, 3 45's, 1x 2-way ball valve, 1 Tee, 1 check valve (head: 10 + 16x 9.8 + 7x 2.5 + 3x 3.8 + 8.8 + .4 + 2.7 = 1674.4')
Rise: approx 25'


Sources
Calculate feet of head: How Do I Calculate Feet of Head for My Pool? - INYOPools.com
ELM Panel info: https://images.inyopools.com/cloud/documents/elm-install-manual.pdf



My Pool Info
Location Northern California (SF Bay Area Peninsula)
Pool 25k gallon in ground (about 600 sq ft surface)
IntelliFlo variable speed pump (installer set at 2800 RPM for solar, 2100 without)
400 sq ft solar (4x 4x10 polypropylene ELM panels with 2" header) on 2nd story
Solar Pipes
to solar: 105' w/ 14x 90°, 6x 45°, 4x couplings and 1x 2-way ball valve
from solar: 105' w/ 16x 90°, 3x 45°, 7x couplings, 1x 2-way ball valve, 1x Tee and 1x check valve
rise: about 25'
Pool Pipes
Don't know much because it's a pre-existing in-ground pool. Pump is only about 8' from pool edge though.
4x 90sq' cartridge filter (A/P Quantum 360) showing about 23 psi
No other heater



Bonus Question
The panels are rated for 4.0 max GPM but it looks like way more pressure is needed to run the system. Am I reading this the wrong way?


Thanks
Thanks for any help. I read the hydraulics 101 and the above sources. If there's somewhere else you could recommend I look that would be very helpful.

 

[CJadamec]

Without a ton of fancy maths the simple answer is your filter is showing 23 psi which means your total dynamic head on the system at that rpm is about 53 feet (1 psi = 0.433 ft). Once the system is installed and running you don't really need to bother with all the plumbing math the discharge pressure of the pump tells you how much head the pump is working against in the real world in real time.

Based on the pump curve from the intelliflo manual I'm assuming you have the standard 3hp intelliflo and not one of the "I" models. At 53 foot/head your pump is moving around 80-100gpm way more than enough to be running your solar panels.

Even if you have an i1 intelliflo (the smallest they make) at 53 feet of dynamic head and 2800 rpm you will be moving around 50 gpm which again is plenty of flow.

 

[Catanzaro]

Chuck:

I like your links, especially your back yard and scenery. Inside your breaker panel is also interesting. Will read up on this over the weekend. Your post reminds me when I was trying to figure out which pump to swap out on the radiant heat in the basement. The dope plumber used 3/8" flex tubing instead of 1/2", which would have made the whole difference in the world. Pools on the other hand work with 1 1/2" plumbing. I am not so convinced that 2" plumbing really makes any bit of a difference in pools as what I have, but it appears that turnover is pretty quick with my set up. Not too get off the subject.

 

[CJadamec]

Thanks for the compliments. The backyard isn't far from complete in my eyes but there is only so much time in the day and nothing about landscaping ever seems to be quick or easy. The inside the panel link is pretty useful basic information, I can't take credit for it tho its not of my own making.

As for 1.5" vs 2" inch plumbing for pools either is fine. Day to day most people with basic pools will never notice the difference. Long term over the life of the pool 2" plumbing will cost less to operate from a pump electrical consumption standpoint. Where the larger sized plumbing really starts to matter is when you get more complex pools with lots of added things like spas, waterfalls, fountains, shear drops, solar installations and the like. All those things need more and more GPM flow out of your pumping system and as you approach the magic number of 60gpm through the system the difference between 1.5" and 2" becomes much more dramatic. The resistance to flow through a pipe is an exponential curve. For 1.5" pipe that curve is relatively flat up to about 60gpm, once you go past 60gpm the resistance to flow shoots up like a rocket.

 

[eegz]

Thanks for the simple rule of thumb (1 psi = 0.433 ft) and calculations. That makes things a lot simpler.

You are correct, it's the 3hp model.

Would you have a good rule of thumb for getting the max heat out of a solar thermal system? Summer is dying down and I only have solar for heating.

I had seen a recommendation to get a system which is 50% of your pool surface area. Mine is all new and about 2/3 of the pool surface and I can barely keep it in the mid 70's with sunny days and outdoor temps in the 80's-90's.

A blanket has zero spousal acceptance factor so I'm looking to see what I can do with the pump alone.

 

[Teald024]

I can barely keep it in the mid 70's with sunny days and outdoor temps in the 80's-90's.

A blanket has zero spousal acceptance factor so I'm looking to see what I can do with the pump alone.

I hate to say it, but the solar cover will do WAY more for your pool than increasing the panel efficiency. Tweaking to get that last couple percent efficiency is a moot issue without a way to keep the heat you have already captured.
As this of your spouse: What is more useful, a pool that looks good but is too cold to swim in OR a pool with a blanket (at night at least) that is warm enough to use? I'd vote for the latter. Maybe a compromise of only using the blanket at night to slow evaporative heat loss. It's not insignificant.

 

[pooldv]

I used to hate solar covers until I got one. We added quite a few weeks to the swim season just adding the solar cover to our solar set up. A small heat pump added a few more weeks. We swam all of October last year and started swimming March 13th this year. We definitely could not do it without the solar cover. More about heating our pool in my pool thread, link in sig.

 

[Swampwoman]

I still hate solar covers but I got one because I decided to try to run all winter in Michigan in an air dome

So, my dome doesn't go up for a week and the temps at night right now are in the 50s (40s tomorrow) and today I had a lovely swim at 90

If you get a good reel, your spouse may come to love-hate covers as I do!