Originally posted by Henk View Post
Thank you. I appreciate your feedback. Our pool is an Intex 16ft (48inch deep). Surface area approx 18 meters. Each current coil is under 1 m2 so I guess you’re suggesting 9 coils/collectors or more. Hmmmm… that’s a lot for a small pool.
Currently we use the sand filter pump (came with the pool) which is able to handle the 1/2 inch pipe, however the salt water system doesn’t like the reduced flow rate. We therefore prefer to get an independent pump to do the job. We noticed this pump on a local New Zealand equivalent of Ebay (http://www.trademe.co.nz/a.aspx?id=+61404532026) and wondered if it will do the job. Specs are assuming 1 inch pipe so we need to know if it will still produce decent rates through a 1/2 inch pipe.
I will check out the suggested website.
You’re most welcome.
I guessed about that size based on H2O vol. and common 4 ft. depth. That’s where the SWAG of collector size came from.
I wasn’t suggesting anything really, and especially not endorsing the coil type arrangement/material you’re using.
Expect a lot more pressure drop == reduced flow rate for smaller dia. tubing —>>> probably 4X pressure drop for reducing dia. by half with same flow velocity. But, check the pump curve for your pump for low rate vs. pressure drop.
Assuming the goal is to keep the pool H2O at a comfortable temp. for as long as possible with the least amount of hassle and money spent, a compromise position (in various iterations) a lot of folks have found involves a bit more $$ but generally less hassle and a better design is to:
1.) First, get a pool cover. They’re cheap, and sort of durable if not stored in the sun when not in use. The bubble wrap type will stop about 1/2 of the heat loss provided the rain /moisture is kept off the cover when on the pool. Or looked at another way, a pool cover can reduce the required collector area by about half for a lot less than the cost of the collectors they replace. They can be a hassle for larger pools but a 16 ft. dia. may be manageable.
2.) Get collectors made for the purpose. Not an endorsement, but check out Fafco on the net. There are others as well. Such units are relatively easy to plumb, usually aren’t considered too unsightly, and perhaps for your considerations, relatively low in pressure drop. Also, they’re usually a lot more efficient in terms of thermal performance. Often used ones are almost as good as new for a lot less money, provided they don’t leak or haven’t been discolored ( “whitish”) by irrigation overspray, etc.
Depending on your flowrate and flow arrangement, the pressure drop you’re likely to incur with coil arrangements as you describe may be quite severe, or at least more than the original system was designed for. Using collectors made for purpose allows the long term avoidance of hassle, maintenance and aesthetics is often considered worth a modest to moderate up front extra cost, particularly when the usually better performance of made for purpose equipment is taken into account.
Not to rain on your parade, but DIY stuff is a great learning experience. Been there, done that. Read/study builitsolar.com and learn from the mistakes of others – you’ll see a lot of stuff, some of which slick. Most of which is also reinventing the wheel in one way or another. I suspect a lot of the stuff wouldn’t exist if the builders had read up a bit before they started. Most of it looks like a good learning experience, sometimes if only from the standpoint of what not to do.
If it was me – and it obviously ain’t – I’d get a cover before any more fooling around with coils of irrigation hose, use it for a season and monitor results. In the meantime, and in the off season, read up on pumps, pressure drop, flow rates etc. and solar pool water heaters made for purpose – it ain’t rocket science. Then, after the season is over, and with your newly acquired knowledge, you’ll have more information if you choose to (or need to) add a pool water heating system. Just remember to leave room and flexibility in the design to be able to add a collector or two if needed.
Knowledge is power. Get some of the first and use it the second to get a well done and fit for purpose system.
FWIW, and with no particular performance warrany expressed or implied, my SWAG would be you’ll be best off with a pool cover and 2 FAFCO 4 X 8 ‘s or 4 X 10’s plumbed in parallel, oriented to face the equator at a tilt about equal to your latitude minus 15 deg. for summer performance, or at about latitude for a bit more pool use during the shoulder seasons of spring/fall.