Im making my first Hot Water Solar Collector to go on the roof and
will be using a 60' roll of 1/2" i.d. Copper Tubing in a 2x6" wooden
box , with a Thermopane Window that comes in a vinyl enclosure frame
to sit on top of the box. Im going to paint the wooden box , copper
tubing roll , and window enclosure frame a flat black using special
high temp. paint intended for Solar Collectors . I suspect the
temperature of the window enclosure frame is going to get very very
hot in the summer , so, im wondering what sort of adhesive or
weatherstripping I should use to seal the window enclosure frame to
the wooden box that will hold up very well in extremely hot temps and
moisture ? Thanks.
Since your box is made of 2x6's...water is going to get in. Consider
in oyur design & fab allowance for liquid water to escape AND water
vapor as well...otherwise you're going to get condensation on the
bottom side of the glass which will interfere with the solar
Good catch on the thermopane glass.....I totally missed that.
I would suggest sizing your collector box such that "free" ancient (as
in no special sunlight transmission inhibiting glass) sliding glass
door panels could used.
If the frames are aluminum (check with a magnet) you can use wood
working tools (saws, drills, etc) to modify the frame.
The window is going to be special ordered with regular glass...not low
'e' or tinted . I want thermopane glass so heat is kept in the
box more instead of escaping. I plan on sealing the vinyl window
frame to the wooden box real well , but I will put in a couple drain
holes in the box in case moisture condenses in it (which I doubt will
Use a j-shaped drain. That way water will hold in the drain to keep
air flow out, but will still drain if water builds up. But, watch out
for condensation building up inside the unit; You may want to have
the whole thing airtight.
Wood absorbes moisture, dry in your home its around 5-11%, outside
maybe 15% dry, on a roof it might be higher and transmit in and
condense, even oil paint is rated for moisture permeability, Sherwin
Williams will get you the info specs on their stuff, I used to have
their spec book, maybe its online. Sheet metal is best, but if wood is
used paint the whole box. SW has good products and will help at the
tech level so you can seal the wood completely, Ive seen collectors
all fogged up. Get glass with a warranty on the seal and fogging, my
local does it. alt.energy.homepower might have panel makers, Read
the "Born On" date on the silicone sealant you buy, it degrades to
sometimes worthless in 6 months, if its an issue finding new contact
manufacturers like Dow, use what they recomend to clean before
caulking. The high heat and humidity will stress everything. One
consideration you may not have though of I can think is wood expands,
and you will get it real hot, that might ruin the glass seal fast as
the frames expands and contracts daily, there again Metal is best, and
sheet metal is cheap. On metal paint should last much longer, it will
be what 160f in the box? think of the wood expanding- contracting
every day. Ive seen doors move 1/16th" a day, every day, painted black
and they wont get as hot nor were they Flat Black which absorbes more
energy. But maybe im wrong im just thinking
When you state "thermopane"...do you mean two layers of glass with a
Depending on the operational temperature of the water in the collector
tubes (pool heater? domestic water? living space?) ....double pane may
actually reduce heat gain
Please post photos of unit after a few days of sun after the rain
My money is on water vapor condensing on the innermost surface of the
Thanks everyone for the tips and considerations. Ill take precautions
on the box being airtight and will coat the wood with a moisture
barrier coating of some sort. Once i get this built and in
operation, ill be posting some results .
I think you are being penny-wise and dollar-foolish in trying to make
this a DIY project. Solar collectors are hi-tech engineering and even
small "errors" can result in huge losses in efficiency or even ruined
collectors -- it doesn't take much leakage to cause condensation which
in turn will destroy efficiency.
It has taken *many* years for big companies and experienced engineers to
get the engineering right so that the conversion is not only efficient
but stays that way for years. Even with the best of companies, they have
to offer long warranties because people doubt the ability of the
collectors to maintain their efficiency over the years of abuse from
hot, cold, sun, rain, snow, acid rain, grime, etc.
Remember that even making a lasting doubl-pane picture window was not an
easy feat and early failure was (and maybe still is) a common problem
until better engineering came up with more lasting solutions. Yet you
are designing something that will go in an even more harsh environment
where it will literally bake all day in the sun and then cool at
night -- repeatedly.
I can't imagine that a DIY solution would even begin to compete with the
know-how, experience, high-tech materials & seals, fabrication tools,
etc. that are available to an experienced manufacturer.
Seems to me like an exercise in frustration in the making...
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