DHW rebuild / insulation [RE-wrenches]

Jeff Yago jryago at earthlink.net
Fri Apr 18 09:45:09 PDT 2003


"....it partially melted down from the heat. What's a more appropriate
insulation to use when I rebuild using new flat plates?"

Kirk:

I did some product design for a commercial flat plate DHW solar panel
manufacture back in the 1970's and we tried many different types of
insulation.  Yes, we did see melting of some types of insulation as these
things get HOT! We measured in excess of 300 degrees F inside the panels
using black chrome plated aluminum absorber fins and empty tubes (no water
flow). This really breaks down most normal building materials over time

We found that a hard compressed fiberglass batt (like duct liner) worked
best, B U T !!, it was a special type that used binders that do not outgas
when heated.

The fiberglass type of insulation could stand up to much higher temperatures
than "foam" type insulation, and the semi-rigid fiberglass sheet(about 2"
thick) gave good support to the large copper absorber plates.

Most types of foam and fiberglass house insulation will not work as they
give off chemicals when heated and these gasses condense and permanently
"fog" the glazing.  This was like painting the underside of the glass which
would reduce the efficiency.

Good luck, but like everything else, its not as simple as it looks!

Jeff Yago

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