Note: The information contained in this periodical weblog may be outdated. This was my personal weblog published before January 1, 2015. Since then I have been the co-owner and Principal Solar Designer at Florida Solar Design Group.

5 Comments

  1. In every aspects we have pros and cons so its not a big deal. Jason I think your post contains a lot of worthy tips and information which will assist every pool heater in the Florida regarding heating pumps. So I will conclude that your post deserves a deep reading a lot of followers. Thanks and I really enjoy your post.

  2. I was curious as to why you didn’t consider the combination of the A/C with the Pool Heating recovery heat exchanger. I think that they are a viable option for Florida folks also.

  3. Author

    Pete – that is an excellent question. The answer has a few of parts:

    1. Air conditioners in homes typically do not run when pool heating is needed the most. In the winter, A/C is rarely used, so no pool heating would occur.

    2. Newer air conditioners put out relatively little heat. As SEER ratings increase, the efficiency rises, so the amount of heat “recovered” is less. When we all had 9 SEER A/C units, heat recovery units for home water heating was pretty popular. With typical SEER ratings nearly double that, the amount of heat generated is low. In fact, we routinely remove heat recovery units from domestic water heaters when installing solar water heaters.

    3. The overall heat provided by an air conditioning unit, even if the timing/demand did line up well, is minuscule compared to the amount of energy required to heat a pool (water). Think of it this way – it takes far, far more energy to heat water than it does to cool air. It would not make economic sense to install the equipment required for heat exchange in this scenario.

    Hopefully that answers your question. One day maybe someone will produce a single compressor unit with dual heat exchangers that can selectively heat a pool or cool a home at different times of the year, but I don’t think attempting to do this simultaneously with a single unit is the best strategy. It would be too hard to do both jobs effectively.

  4. Great Site. I’ve been learning a lot.

    I just payed $5.39/g for LP in Mid May, midwest Florida!!!! I went out to my tank and turned off the gas. So I bought four 4 X 12 Fafco Revolution panels to work on bringing up my temp a few degrees. Two are connected so far and I haven’t noticed much increase in temp today which is the first day I have run the panels. I will be putting the 2 other panels up next weekend. I am currently at 77 degrees water temp inside a birdcage with a fair amount of shade covering the pool. I have a 20K gallon running a single speed pump. Plumbing is 2 inches through the panels, but needed to reduce to 1 1/2 since all my other plumbing is from the late 80’s.

    I have read about flow rates and you have mentioned some flow metering for variable speed pumps, but how about for 1 speed? Can I control flow rates to benefit my set up by half opening the ball valves to the intake of the panels to slow my flow?

    What is the effect on water pressure by adding more panels? And how does adding another panel affect flow rates? Will 4 panels be effective for my goals?

    THank you for the great blog

    1. Author

      Dan,

      Was you system installed be an authorized FAFCO dealer, or is this a DIY system?

      One point – you should use 2″ plumbing for the entire collector loop (up the wall and on the roof and all bypass and isolation valves) to get the best performance (most flow). Hopefully you did not use 1-1/2″ right up to the collector headers.

      To answer your questions:

      It sounds like you are trying to reduce flow through the panels. There is a common misconception that you want to slow down the water the get the greatest heat rise in the panels. That is generally not the case. Higher flow rates (to a point) result in better overall heating performance. You want to move a lot of water with a small temperature rise. Solar thermal collectors become less efficient as they get relatively warmer. At a certain point, the temperature rise may become so low that it is lost in the return plumbing. You are looking for about 8 gallons per minute in the collector loop. With only two panels, you may want to open the bypass partially as you suggested. A flow meter helps tremendously with this. The effect on water pressure for more panels should be negligible. Since you are adding panels in parallel, not series, there will be little effect on the overall flow rate. The flow rate per panel will be less, but overall flow rate will not change substantially. System sizing is a bit complicated since there are so many factors involved. A 20k gallon pool is pretty large for Florida, and a six panel system may be undersized in many cases. It all depends on your desired temperature and the other complex factors involved. If there is enough roof space, we often see 8-12 panels on a 20k gallon pool being the best solution.

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