Will an unglazed panel work

Discussion in 'Solar and Geothermal Water Heating Forum' started by diyer23, Aug 20, 2009.

  1. diyer23

    diyer23 New Member

    Jul 21, 2008
    I am researching solar water systems for my South Florida home. I am looking at an open loop flat plate system utilizing my current electric hot water heater as a storage tank. I estimate I will need at least 30 sqft of collector. I have found a used 48 sqft unglazed pool collector for almost nothing on craigslist. This could save me $800-$900 over a new glazed collector. Do you think an unglazed collector can get the water hot enough for home use?
  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    It will get it hot because the tubes are black and will absorb energy, but the closed cell that glazing provides increases the heat buildup much faster. Check the cost of two 4'x4' tempered glass panes, if that unit is 4' x 8'.
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  4. Master Plumber Mark

    Master Plumber Mark Master Plumber

    Feb 6, 2005
    Sensitivity trainer.. plumber of mens souls
    indianapolis indiana - land of the free, home of
    how cheap is cheap??

    It has got to work in Florida....

    as long as you are not buying someones junk..
  5. usesolar

    usesolar New Member

    Aug 25, 2009
    solar researcher
    Solar Pool Collector

    You might want to reconsider collector for hot water use . A unglazed pool collector is designed for 15 to 20 degrees above ambient air temperature, where a flat plate collector for hot water system is designed for 25 to 125 degrees above ambient temperature. Solar water storage should be at about 140 degrees. Good luck!

    Good time to take advantage of solar credits!
  6. Dana

    Dana In the trades

    Jan 14, 2009

    What he said!

    Put another way: Pool heaters are not designed to run at the higher temps- without glazing they become dramatically less efficient with higher delta-Ts. They're not designed for potable water use anyway- you'd have to run with heat exchangers.

    Pool heaters are great for low-temp applications, but not domestic hot water. When it's a cool-no-frigid 50F out you won't get ANYTHING out of a pool heater at 120F + DHW temps (even if you had 1000 square feet of collector- the stagnation temp at zero flow will probably barely hit 120F on 50F days), but you might still muster some 80F output for maintaining the pool. By comparison a glazed collector is still going to deliver at least some performance down to well-under freezing, and very solid performance at 50F & above. (When it's a toasty 100F outside a pool heater should will deliver pretty good 120F output though. :) ) See:


    Glazed collectors show up on Craigslist for cheap too, but by the time you've tested & installed the system it may not be cheaper than going with a tax & utility-rebate subsidized new unit. If you're hell-bent on tinkering, wait for a glazed collector for the DHW, save the pool heaters for pools and other low temp low delta-T apps where they can run with decent efficiency. (I've seen 'em used for driveway snow-melting apps in New England, where 40-45F output on a 15-20F afternoon is good enough for the task at hand.)
  7. flamefix

    flamefix New Member

    Sep 4, 2009
    Heating engineer in the UK licensed to fit service
    Exeter, England
    That's reason enough not to. do you really want to run the risk of contamination and bacterial growth, I doubt your water supplier would be too happy to say the least.

    You can save money but not at the risk to your health.
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