Some background : I live alone and want to totally eliminate the need
to run my 40 gallon electric water heater, and since i live in sunny
Florida I believe I can do so given my low requirement for hot water.
Im going to be building my solar collector very soon when all the
materials are gathered. My requirement for hot water usage is to take
a relatively quick shower of 5-10 minutes using 100 f. hot water and
believe the following plan will handle at least that :
I want to use 3/4"x300' coiled red Pex Tubing which measures 32"
diameter x 7" high . I will set this in a box which i will construct
out of wooden 2x12's with a 1/2" thick plywood on the backside
(treated) for a 36"x36" od Box. . I will lay 4" of dense pink
Foamboard in the bottom . A 32" square sheetmetal plate painted with
flat high temp. low gloss Black paint (primed first) will be layed on
top of the bottom Foamboard . The coiled Pex tubing will be wrapped in
heavy duty tin foil sheet to prevent UV light from seeing the Pex ,
and this foil will be pulled tight around the coil of Pex and also
painted high temp flat black. ... then the coil will sit inside the
box in direct contact with the sheetmetal plate. A double pane window
in frame measuring 36" sq. od (without any inside bars) will be
fastened on top of the box for a greenhouse effect. The box will sit
against the southside of the house on the ground at a 30 degree angle
from vertical in a location where where it will recieve full sun. I
will cut the hot water CPVC pipe above the water heater and route to
the Solar Panel using 3/4" CPVC (insulated) connecting to the 3/4" Pex
tubing stubbed out of the side of the Box using Pex compression
fittings . The return CPVC pipe (insulated) will run back to the top
of the water heaters hot water supply pipe. (Since my hot water
reqirements are very minimal, I opted not to heat the entire water
Since stagnation temps/pressure in the box are of concern, i plan on
securing a section of shiny sheetmetal over the face of the Box for
capacity control during the summer months.
Specs on the Pex are 100 psi at 200 f. Specs on the CPVC pipe are 100
psi at 180 f. May aim is to deliver hot water in the 100-120 f. range
thru experimenting with how much to cover the front of the Box with
the shiny sheetmetal plate .
Total estimated cost for this project is $300 ($100 for the Window ,
$120 for the coiled Pex, and $80 for the wood and CPVC piping with
If you have tips, considerations, concerns, etc... I would love to
hear them. Thanks. Dave.