swimming pool solar heater question

[john]

I am considering purchasing a solar heater for my 13,000 gallon inground pool. The system I have picked is from "SmartPool". My questions is this:

Currently I have a 3/4 HP Hayward pump with a sand filter. To use this solar system I will have to pump the water 12 feet horizontally and 15 feet vertically to reach the roof of my house (which is where the solar heaters will be). Is a 3/4 HP pump strong enough to do this? The vendors website says that a 1HP is plenty for this application, but doesn't say anything specifically for any smaller pumps. I do run this pump 24 hours/day during the summer so the smaller the pump, the less expensive it is to run the pool. Any experiences or thoughts out there?

[Dan Espen]

No experience but a 1HP motor will run about $150:

I'd be inclined to try the 3/4 (why just throw it out). The worst that will happen is that it burns up. If the flow seems too slow, put in the 1HP.

As for running the pump 24 hours, they make timers for pools. There's really no reason to run them 24 hours a day.

Wish I had a place to put a solar setup. I'm using NG.

[trader4]

Plus the difference in electric usage for a 3/4hp pump vs a 1hp pump doing the same work isn't going to be very much. The actual electric used depends more on the work being done than the difference in rated hp, so if they run at the same RPM, move the same amount of water, etc, usage is gonna be pretty close.

[Bubba]

Your 3/4hp will be more than enough. You will only lose a slight amount of capacity due to the friction loss. Use as few a elbows as you can and make those elbows long radius. The height isnt a factor really. Once you purge the air from the line, all you are doing is moving the water. I can move water 3 stories high with only a 1/20hp mini pump. You will also find that approx 8 hrs of run time for a pool pump should be enough to turn over the water in you pool if sized properly. This time will vary with higher water temps, humidity and bather load. You might also want to make sure you have plenty of sun during the times you want that water warm. Grey days, clouds and rainy gloomy times arent much for producing 10 degree warmer water. Bubba

[gfretwell]

I agree 3/4 is plenty and if you run it the whole time you are producing solar heat you will have plenty of turnover, even with the reduced flow. One thing I did was to put a garden variety HVAC thermostat (weatherproof box) in line with the pump, via a contactor, so it only runs if the outside temp is high enough to help you. If your pool is not covered you won't be able to get much above ambient air temp, no matter how many panels you have. The thermostat is about as good a predictor as a lot more expensive solution will give you and easy to adjust for the desired result

[Stretch]

One thing I did was to put a garden variety HVAC thermostat (weatherproof box) in line with the pump, via a contactor, so it only runs if the outside temp is high enough to help you. If your pool is not covered you won't be able to get much above ambient air temp, no matter how many panels you have. The thermostat is about as good a predictor as a lot more expensive solution will give you and easy to adjust for the desired result

A solar pool heater works off heat absorbed from sunlight, not from ambient air temperature. We had a solar domestic water heater whem I was in Pennsylvania. It produced a maximum of 177 degrees F domestic hot water during the summer. It was no where near that hot outside. The solar pool heater should have all the controls it needs built in. When I did solar pool heaters, we used FAFCO brand, they worked great.

As far as the pump wurking in your application John, You would have to look at a pump curve. The pool heater manufacturer can tell you how much flow you need at what head to push through their pool heater panels. Since pool heaters are using water open to the atmosphere, you need that dynamic head plus the head for the existing piping plus the

15 feet vertical static head for the panel height. So if you have a low head, high flow pump, it may not work.

But you can always try it any how if you wish.

Stretch

[gfretwell]

If your pool is not covered it will lose heat from the surface faster than the panels can put it in if you have a significant delta between water and air.. Your domestic hot water uses glazed collectors and an insulated tank. Different animal.

[Richard J Kinch]

No, it works by not giving the heat back from the pool to the ambient air, when the ambient air is warm enough. Thus the thermostat is a good idea. Kind of silly to pay to heat a pool when it is 40 deg F out.

[Edwin Pawlowski]

Your opinion. Some idiots will swim in heated water when it is that cold out.

[Stretch]

When I was in Pennsylvania, we installed over a dozen FAFCO solar pool heaters. All were installed on outside pools, including 2 at country clubs. They only covered those pools at night, during the day they were in use and worked just fine even in cool weather.. The amount of heat generated depends on the number and size of the panels. The amount of heat needed is mostly determined by the surface area of the pool exposed to the air (and the pool water temperature). Because of the low temperature difference between pool temperature and outside air temperature, these things work great.

Richard and gfretw, how many solar pool heaters have you installed? Maybe things have changed since I left Pennsylvania.

Stretch

[Richard J Kinch]

No, you miss the point. It won't *be* heated with that ambient.

[AZ Nomad]

Depends on the pool and the heaters.

[Richard J Kinch]

Cripes, we're talking about the OP's pool and heaters. Not the universe of pools and pool heating.

[gfretwell]

"How many" is not as important as what are you doing right now. I have a 12 month pool in Florida with solars and I watch the effect of the solars pretty closely. I have figured out if the daytime air temp is colder than the water temp I am wasting money turning on the pump to run the solars. In fact I really don't see significant heat gain unless it is a few degrees warmer than the water. That's why I added a thermostat looking at the air temp. I have about 60% as much collector as I have water surface and the pool is not covered. A bubble pack cover will make a huge difference but I don't want to screw with one. Bottom line is my solars give me about 2 extra months of reasonable swimming (mid 70s f) and another month of "canadian lake" swimming (low 70s). If I was willing to screw with a cover, like my neighbor, I would have water at 80 or more all year. At a certain point it is too cold to get OUT of the pool.

My next plan, try to heat exchange the attic.

[Stretch]

"How many" is not as important as what are you doing right now. I have a 12 month pool in Florida with solars and I watch the effect of the solars pretty closely. I have figured out if the daytime air temp is colder than the water temp I am wasting money turning on the pump to run the solars. In fact I really don't see significant heat gain unless it is a few degrees warmer than the water. That's why I added a thermostat looking at the air temp. I have about 60% as much collector as I have water surface and the pool is not covered. A bubble pack cover will make a huge difference but I don't want to screw with one. Bottom line is my solars give me about 2 extra months of reasonable swimming (mid 70s f) and another month of "canadian lake" swimming (low 70s). If I was willing to screw with a cover, like my neighbor, I would have water at 80 or more all year. At a certain point it is too cold to get OUT of the pool.

working on ambient air temperature, not solar gain. May as well put your wxisting panels inside your attic. How many square feet of panel per square feet of pool surface are you using. It sounds like you need more panels. Or more efficient panels. And maybe a bigger pump.

Stretch

[Fred]

I have a 3/4 HP (full rated) Hayward Super II pump, 1-1/2 inch pipes, and oversize sand filter for a 22,000 gal pool with a similar lift to the solar panels. It works OK but I generally can't get flow if I'm connected to the solar panels when I start up. I have to start pumping direct to the pool before manually swapping to the solar panels. Air leaks that allow water to drain back down to pool level when the pump is off are a killer. If you can keep water in the line from pool to pump, you may be fine. The system is marginal. Running

24/7 obviously avoids my unattended startup problems.

What you need to consider is the pump design. The pump mechanism may be designed as either a high flow - low head pump which is not good for lifting to solar panels, or a medium flow - high head pump. You would need to check the pump curves for your model. Here is a link to a set of Hayward pump curves.

Note that the Super II has steep curves compared to the Super. If you assume 40 gpm flow (near upper end for 1-1/2 inch pipe) with SP3005(x7), the Super II flow would be reduced to about 25 gpm when adding an extra 15 ft of head loss while the Super, SP2605(x7), would be reduced to no flow. If you have a Hayward pump other than the Super II, you may be out of luck given how marginal my setup is. If your flow is lower (e.g. you have 1-1/4 inch pipes and 30 gpm flow), you may be pushing the limits of the Super II 3/4 HP. But as others say, try it. The other options are to do a detail pump head loss calculation or to run an experiment where you connect up pipe to your pump, stick it up in the air 20 ft and see if you can pump water out the top (smile - my approach).

[Bob G.]

========================= Play with it since you can always run a boaster pump if needed ...just remember that you are after a failrly slow flow rate thru the solar panels.....

However Why would you even think about running the pump 24 hours/day That would defeat the entire purpose of heating the pool ...you would be heating during the day and cooling during the night... Only night time operation I can think of is during a heat wave in the middle of summer and you wanted to cool the pool water down...

Just some thoughts ..

Bob G.

[JimR]

Most / all solar panel systems have an automatic shut-off valve which doesn't allow the water to circulate through the solar panels when they're not producing heat. Any pump that would be running from late day to the next morning would be doing pool filtering only, since the water would not be sent to the solar panels.