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Re: Evaporative cooling for roof and outside AC unit

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  • Todd
    Ooops. I forgot to mention the AC unit mist cooling idea. My building has two AC units: one for the office area downstairs and one for my loft apartment
    Message 1 of 4 , Apr 15, 2006
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      Ooops. I forgot to mention the AC unit mist cooling idea.

      My building has two AC units: one for the office area downstairs and
      one for my loft apartment upstairs. My loft already has enough
      ceiling and roof insulation to rule out using the evaporative
      cooling idea on the flat roof surface, but the AC unit is up there.

      Last year I installed a shade screen on the South and West sides,
      open on the bottom 18" for air intake and open on the top for
      exhaust.

      This year I want to add a water mist to cool off the outside unit.
      I've heard folks talk about a solenoid triggered off the 24v signal
      from the thermostat to the outside fan unit. Basically, when the
      outside unit is running, the water is spraying.

      The idea is to cool the outside unit by evaporation, thus lowering
      the head pressure and supposedly lowering the AC air temp inside.

      Does the Central AC have enough 24v signal strength to add a
      solenoid valve to it... to control the water flow?

      What size mist heads? Do I need to go as low as a .5gph or .75gph
      like the mist cooling systems use?

      I plan to add a 200 line filter and have seen the phosphate
      cartridges to prevent scale buildup on the AC unit. Suggestions?

      By the way, I applied white mobile home roof coating years ago and
      it made a tremendous difference.

      Todd
    • Paul Archer
      555 timers can be found at prety much any electronics supply house, for example, Mouser Electronics (www.mouser.com) for less than the cost of shipping.
      Message 2 of 4 , Apr 16, 2006
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        555 timers can be found at prety much any electronics supply house, for
        example, Mouser Electronics (www.mouser.com) for less than the cost of
        shipping. However, I'd suggest going the X10 route. For about $30 or so, you
        can get from X10.com either an appliance module or a "universal" module
        (depending on your setup) to actually turn your valve on and off, and an
        "Activehome" computer interface. you can set the interface up however you
        like, and even remove it from the computer.
        It's not quite a turnkey solution, but it's pretty close.

        Paul Archer


        Yesterday, Todd wrote:

        > Last summer some HREG members mentioned significant savings by
        > installing a roof watering system. I'm wanting to rig up one in
        > preparation for this summer's blistering heat.
        >
        > I live in an old building in downtown Monroe, LA, with a flat roof
        > over my shop. This part of the roof has no insulation. It is 30' x
        > 50' My plan is to have a thermostat, timer and solenoid to allow an
        > alternating water/evaporation routine.
        >
        > Basically, 10 seconds water spray, 10 minutes off for evaporation.
        >
        > Some have mentioned using a 555 electronic timer, available at Radio
        > Shack. Well, they don't carry those anymore. What do y'all suggest
        > for the timer? Please give specific part numbers or resources.
        > This is not my strong area.
        >
        > Beyond a timer, I'm thinking of a in-line valve like they use in
        > irrigation such as a Toro 3/4" 24AC valve from Home Depot. Part
        > number: 53380, store SKU 167555, price $13.97.
        >
        > Home Depot also has a valve from Orbit (model 57223, SKU 794864,
        > $10.99) that is referred to as a "3/4" FIP Electric Anti-Siphon
        > Inline Valve with Flow Control." I'm assuming this is still a
        > solenoid valve that also has anti-siphoning. Right?
        >
        > A buddy used a timer designed for attic fans. He got the
        > model#2E340 attic fan thermostat from Grainger's at $21.75.
        >
        > I still need some sort of timer to control the 10 sec on/ 10 min.
        > off.
        >
        > Any ideas?
        >
        > Todd T
        >
        >
        >
        >
        >
        >
        >
        > Yahoo! Groups Links
        >
        >
        >
        >
        >
        >



        -----------------------------------------------------------
        If you live in a small town /You might meet a dozen or two/
        Young alien types /Who step out /And dare to declare/
        "We're through being cool." -- Devo, "Through Being Cool"
        -----------------------------------------------------------
      • larry
        Most of the new high SEER rated AC units have larger condensing coils, and smaller compressors, and matching with a large inside coil. We have have added a
        Message 3 of 4 , Apr 16, 2006
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          Most of the new high SEER rated AC units have larger condensing coils, and
          smaller compressors, and matching with a large inside coil.

          We have have added a secondary condensing coil to our units, with solar
          operated fan. The secondary coil was from an old 3 ton unit (obtained for
          free). The compressor and fan were removed, and then connected in line with
          exiting condensing coil. The head pressure was reduced significantly and
          AMP usage dropped 2-3 amps. Other things we did were run the high and low
          side lines together and insulated heavily from condensing unit to
          evaporator. The low side (cold will help cool down high side line. Recommend
          insulating both lines, attics are hot and will effect high side line. We
          are also adding a water cooling unit (simple heat exchanger) which obtains
          water from the drain pan in attic, the water is already chilled and cools
          down high side. After running through exchanger, water is diverted to
          landscape watering.

          larry



          On 4/15/06 4:39 PM, "Todd" <toddt58@...> wrote:

          > Ooops. I forgot to mention the AC unit mist cooling idea.
          >
          > My building has two AC units: one for the office area downstairs and
          > one for my loft apartment upstairs. My loft already has enough
          > ceiling and roof insulation to rule out using the evaporative
          > cooling idea on the flat roof surface, but the AC unit is up there.
          >
          > Last year I installed a shade screen on the South and West sides,
          > open on the bottom 18" for air intake and open on the top for
          > exhaust.
          >
          > This year I want to add a water mist to cool off the outside unit.
          > I've heard folks talk about a solenoid triggered off the 24v signal
          > from the thermostat to the outside fan unit. Basically, when the
          > outside unit is running, the water is spraying.
          >
          > The idea is to cool the outside unit by evaporation, thus lowering
          > the head pressure and supposedly lowering the AC air temp inside.
          >
          > Does the Central AC have enough 24v signal strength to add a
          > solenoid valve to it... to control the water flow?
          >
          > What size mist heads? Do I need to go as low as a .5gph or .75gph
          > like the mist cooling systems use?
          >
          > I plan to add a 200 line filter and have seen the phosphate
          > cartridges to prevent scale buildup on the AC unit. Suggestions?
          >
          > By the way, I applied white mobile home roof coating years ago and
          > it made a tremendous difference.
          >
          > Todd
          >
          >
          >
          >
          >
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
          >
          >

          Naturallighting.com
          1939 Richvale
          Houston, Texas 77062

          Toll Free 1.888.900.6830
          FAX 281.488.0823

          email: larry@...
          http://www.naturallighting.com
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