SmartThings Swimming Pool Solar Heat Automation - DIY

As a safety net for the battery dieing (or other reasons for the sensor going offline), you might want to consider adding something like this to you piston. It’s saved me a few times when the AA batteries on my modified sensors die.

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That’s a great idea. I’ll take a look at adding that for all the sensors. They are all solar charged now (5 of them) and have been quite reliable…however anyone using ST for awhile now knows that issues arise from time to time.

The HUE light system is the only automation bit that has required zero fiddling/resets/frustration since installation 3-4 years ago. I have about 30 lights on their hub.

Here is a pile of 2022 data that should help the next guy put together an efficient and high performing solar pool “DIY” heating system. I’ve been tweaking on the system now for five years, so it’s getting more and more efficient. I had to order new steel cross pieces and vertical posts for the pool (the new ones will fit the older pools) which are now powder coated inside and out. The old ones were not internally coated and rusted out after four years of use with salt water :frowning:

I’ve simplified the pool plumbing to the first four panels by removing the internal flow restrictions in each of the intake tubes on the four lower collectors, and removed basically a plumbed in manifold. The end result is much better flow to the lower four collectors which drape over the lower roof. We also set a new record last week raising the pool temperature 10 F in 1 day. That’s 583K BTU in to raise 7000 US gallons by 10 F.

I have two pumps running in series (Intex OEM pump + 2 speed 1HP pool pump) to provide enough flow/pressure to supply the panel array/filter and ran a few tests of flow with the new plumbing setup into the current setup of 8 2’x20’ panels, 320 sq/ft.

Low Speed, both pumps 17.5s 5 US gallons (with solar) using 5.3 amps@120V :
1028 GPH total
= 17.14 GPM total
= 2.14 GPM/panel

High speed both pumps 10.5 seconds for 5 US gallons (with solar) at 11.4 amps@120V :
1714 GPH total
= 28.51 GPM total
= 3.57 GPM/panel

If you research ideal flow for this type of solar collector, most sources report 4 GPM (gallons per minute), per 40 sq/ft panel (0.1 GPM per sq/ft) is the most efficient balance between power use on the pumps, and energy gathering from the panels. I ran some tests on a sun/cloud type day, with air temps at about 72 F, around 2pm.

At 2.14 GPM/panel, the best we did was 75K BTU, with a 10 F difference between input/output temps.

At 3.57 GPM, output jumped to 100K BTU, although temperature rise (input vs output) dropped, as you’d expect with higher flow, to about 7F. This pretty much demonstrates the fact that you don’t want high temps in the panels, as they lose a lot of efficiency when you exceed ambient temps (the panels start losing heat to radiation).

So the good news is the panels now output over 100K BTU, and we have yet to see a day with temps over 74 F. The theoretical max for this setup (capturing 100% of the sun’s energy) is 136K BTU. I expect we will see 110 BTU on the system, which would work out to about 80% efficiency. Not bad at all!

The next tweak will be to try two Intex pumps in series to lower the power use of the pump combination. I’ve found that the Intex (pump that came with the pool) uses only 1.4 amps and is rated at 1600 GPH. I’ve tested it in the current system (solar panels off, but flowing through the sand filter) using 1.4 amps, but flowing 1200 GPH. Meanwhile the 2 speed pump is running at 4 amps at low speed, but only moving 750 GPH. I’ve ordered another Intex pump which I pieced together from the Intex site (replacement parts) which is rated at 2100 GPH (1600 when connected to filter) and uses 2.1 amps. The Intex pumps move a lot more water with far less power use than the 2 speed pool pump, so my hope is that we’ll get down to 3.5 amps (vs 11.4 amps) of power use while moving close to 4 GPM for each panel.

These two parts will get you a working 2022 Intex pump rated at 2100 GPM:
INTEX Pump Motor and Control for 12in Sand Filter Pump 26645 ORG SP 12491EG ($ 105 USD)
INTEX Pre-Filter Assembly for 28645,28646 ($19)

Those bits get you a working (2022 spec) pump for $125. If this experiment works, we should have the correct flow, but with power use more in line with a $1500 variable speed pool pump using two inexpensive Intex pumps in series.

Here is a snapshot of data from June 10, 2022 from https://www.hundredgraphs.com/public/denwood

New solar charged SmartThings roof temp sensor

New solar charged Fibaro door sensor with DS18B20 external temp probe. Rare earth magnets (hot glue’d to the rear of the housing) hold it to one of the pool vertical steel supports (shown here on the ladder). The WEBCORE code checks the water temp vs the roof temp and fires up the pumps when there is a 10 F difference.

About an hour of prep setup, to address a bad connection on one of the ABS feed pipes:

The current panel setup:

Taken around 11 am so you can see just how shaded this pool is…

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We set a new “record” for BTU output on the system at 104K BTU. Highest output for this installation is consistently in the 12:30 pm to 3:30pm window. This data was captured at 1:04 pm. Pool temps are now staying in the 80 to 84 F range as nights are warmer, and BTU loss is less.

You can click the image for live data from the system :slight_smile:

I’ve been bugged a bit by how much power the solar pool system eats up with the 2 speed (10 amp@120V) pump in series with the OEM Intex pump (about 2 amps) and the 12" sand filter. That got us to about 1714 GPH (or 3.57 GPM per solar pool heating panel). I was intrigued by how little power the Intex 2100 GPH SF-80110-1 pump consumed and wondered if just putting two in series would get me similar flow, but with far less power use. Power use ramps up quite a bit with flow, and it’s not a linear relationship.

Anyway, I ordered up a new pump from Intex using their replacement parts site:

INTEX Pump Motor and Control for 12in Sand Filter Pump 26645 ORG SP 12491EG ($ 105 USD)
INTEX Pre-Filter Assembly for 28645,28646 ($19 USD)

The above two parts gets you a working pump 2100 GPH pump (SF-80110-2) for about $124. These newer Intex pumps have a digital timer and can also be set for continuous operation. More importantly the GFCI plug and pump will revert to a powered state after power is cut to them…in my case by my Zwave outdoor plug. This has not been the case for some of their older products, which was a real PITA to work around. The first unit arrived DOA, however Intex replaced it with no issues or cost to me.

I also ordered up a 21" Hayward sand filter to reduce system pressure. This is quite a bit larger than the 12" sand filter, (.7 sq/t filter surface) with a lot more filter surface area (about 2.7 sq/ft)…so it offers up less resistance than a smaller unit.

I won’t post up all my test results, but here is the skinny.

The previous setup using a 2 speed pool pump (10amps@120V on high speed), in series with the Intex SF 80110-1 pump, (2 amps@120V) and 12" sand filter flowed a decent 1714 GPH through the system with solar panels in the loop. This works out to 3.57 GPM to each of the eight panels. It used about 12.8 amps (about 1500 watts) with the salt water chlorinator on.

The new setup has one Intex pump before the 21" Hayward sand filter, and the 2nd Intex pump after the sand filter. They are plumbed essentially in series. Flow is now 1765 GPH, or 3.67 GPM per each of the eight solar panels. The big difference is that the system only uses 4.32 amps (about 494 watts) or 3.72 amps after the chlorinator completes it’s 2 hour daily cycle. For anyone counting, that’s 67% less power use during peak power rates in the afternoon! I also found an amazon sourced “intex” hose in the mix that was only 1" ID. The correct Intex hoses are 1.5" ID, so pulling that out of the mix, did make a small difference too. In any case, I’m pretty happy that we’re close to the ideal flow rate/solar panel of 4 GPM, but with power use reduced 67%. Coolio! I calculated that the system tweaks drop the actual cost per month from about $50, to $17.

At this flow rate, the pool is fully filtered (with solar panels in the loop) every four hours. On an average day, the system runs for 7-8 hours, so we’re in good shape to keep the water clean and warm too :slight_smile:

I would summarize the “hot tips” as follows:

  1. Make sure all of your hoses and plumbing are 1.5" ID.
  2. Use a larger sand filter. I bought a 21", but I suspect a 16" unit would have been fine too for my situation with a 7000 gallon pool.
  3. If using two pumps in series as I am, plumb one in before the sand filter, and the other after it. This made a substantial difference in system flow.
  4. Use the Game Intex 40mm to 1.5" plumbing adapters (for running hard pipe), and order 1.5" Intex hoses directly from Intex’s site…they are much cheaper to buy this way.

Here’s the latest setup:

System power use with the chlorinator off:

And with chlorinator on:

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Your write-ups have been fascinating to follow along with! There’s not been a lot of discussion in this thread, but hopefully you’re still motivated to keep these kinds of posts coming!

I have a 15’ pool, and just upgraded the tiny original pump/filter to a much larger sand filter & pump. It’s made a huge difference in keeping the pool clean. But I don’t have any of the fancy solar heating or anything, just the basic plumbing right next to the pool. Maybe someday I’ll be sufficiently motivated to make things fancier!

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Steven (@iridris ), normally I would stop posting (with low discussion), however I figure that I’ve used the internet to answer a lot of questions. Accordingly, I post information that I’ve typically not been able to find, so that the next person can use this information for their own installation. At this point honestly the pool is more of a science experiment for me versus an essential family leisure activity…ha. I’ve learned a lot about solar energy and pool science over the last few years.

The Hundredgraphs site created by @ipstas has been a great tool to monitor things, essentially motivating me to tweak when I see that our actual solar gain is less than 85% of the theoretical (100% efficiency) gain. In any case, I appreciate you replying here as it does provide motivation! I figure the pool installation is about as far along as I can take it now, without plunking down $1400 CAD for a variable speed pump. At higher pumping volumes needed for solar (where variable speed pumps use more power), I’m not sure the power savings would justify one.

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As always. happy to be helpful :wink:

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