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I took the opportunity to throw-out my 20 year old 2 hp pump and installed a 3/4 hp Hayward Northstar. I probably could have gotten away with a 1/2 hp Northstar and saved even more $$ on monthly operating costs.
I'm not sure what you mean by your second question - the panels get full exposure being on the second story, so it is an optimal installation.
pj
I thought mounting the panel on the second story roof was too high.
Too high? Closer to the sun!
The only problem with height (aside from having to work on the second story whilst being affected with acrophobia) is the pump head issue. Is that your concern?
If so, you are certainly correct - it is very important that this issue is addressed. More broadly, the pressures throughout the system must be calculated during the design phase - *not* later.
As far as the roof height is concerned, your pump needs to be able to lift water to the very top of the panels (i.e., the highest point which is the outlet). My outlet is at 25', which is about 11 psi...easily handled by my pump (this is exactly why I say I probably could have downsized the pump even further to 1/2 hp).
The next crucial issue to address is this: you need to tie-in the solar panel outlet into a spot in your return system that is at a *lower* pressure than the pressure generated by the head of your solar panel outlet. The larger your pump, the harder it will be to find this spot. Unless, of course, you have a completely separate return pipe that you can dedicate to the solar.
This is the reason that I strongly encourage anyone who is contemplating this project to examine the webpage on www.powermat.com that addresses mechanical and plumbing design. It clearly explains the issues (with diagrams) that I have only touched upon.
HTH,
pj
why would the height add to the head? it has to come back down... adding to the equal and opposite head? no?Quote:
Originally Posted by pj1016
coreyinsocal - I'm not pj1016 but:
Your right once the system is filled with water less head is needed to keep it moving. But usually there is a vacuum break valve high in the system so the water drains back into the pool when the system is off (for winter freeze protection). So you need a pump that has enough head to pump all that water up to and over the top everytime it starts.
How many square feet of panels do you have???
I have 640 square feet of pool and heat them VERY nicely with 240 square feet of panels. During the heat wave my son forgot to turn them off and the water hit 98 degrees!
Why do you need so much? Are you in Northern Alaska and looking to extend your swimming season beyond the 4th of July?
Two comments:
Drain back is NOT just for "winter freeze protection". It is designed to take a HUGE load off of the panels and your roof when the panels are not generating. If you took a 2 liter soda bottle, filled it with water, attached a hose filled with water, stuck the end in your pool and lifted the bottle, at some point, the bottle would collapse due to the pressure created by the water trying to go down! The same forces are present in a closed solar system - the higher you go (2nd story like mine), the more pressure. Letting the system drain back is like punching a small hole in that bottle, the water drains back, the pressure is relieved and your bottle (or in the real world, your expensive solar panels) DON'T collapse. So, as discussed above, your pump needs to be able to lift water to the highest point in your solar system, in my case that is about 35 or so feet.
As for more is better. I have 55% coverage (450 ft on an 800 ft pool) and would like more. Two reasons, my panels face slightly northeast (only place on the house they could be put), so they generate wonderfully when active, but they are active probably 2 hours a day less than if we had an optimum south/southeast exposure. The 2nd reason is recovery time. When we get a very cold night (we have had nights into the high 40s, low 50s here in lower NY), the pool loses a lot of heat (we don't cover it in during summer, I know that is a big part of it). We can recover about 4 to 5 degrees per day on most days. If we added 50% more panels (maybe on the garage, next year), we would get 6 to maybe 9 per day. That lets us recover from a really cold night or a cold rain storm in one day, instead of 2 or 3. That would be NICE.
Simons99, I think you are fine. You will have 80% coverage, so even on a north/west facing exposure, you should have great generation. That is about the percentage I hope to get to next year by adding a 2nd set of panels of the garage roof.
Don't get me wrong, I am THRILLED with our solar, we shut the system off when we were getting water at 90 consistently. Its just that with the weather so variable here in NY, I think quick recovery time is probably more important than in other areas of the country.