Solar thermal panels for drainback systems

Erico

Dear Dan,

First of all I have to make clear that I had to cheat with my address in order to be able to log. Impossible to do so in your form, If I live "in the rest of the world".

My question is as follows: I live in Argentina, where no solar wholesalers exist.

To buy here Solar thermal panels for a drainback system I am trying to build, I have only 2 options. Both mineral wool insulated, grid/harp type, etc. German Rehau WK and spanish Ariston Karios CF 2.0

Both form part of established kits these firms sell of indirect glycol systems, and insist, that although "in theory" they have what I need, none is "prepared" to operate in drainback systems. No further explanations.

¿Can you tell me what conditions, appart from the evident ones, thermal panels should have to be used in a drainback system?

¿Are some too fragile to sustain mechanical expansion and contraction effects due to changes in temperature empty or filling up in the cycles? Do they vary according to surface treatment of absorber plates, in withstanding high temperatures? ¿Have some of them more oil in their mineral wool that evaporates at let's say 200ºC? ¿Evaporation of adhesives used to fix in place isolation? All of this clinging to the undersurface of the solar glass, and corrosion effects of hot mineral oil? etc..........

If you know, please tell me. These considerations may also avoid mistakes, when buying panels for such systems, of many others !!!!! Thank you, Eric

hot_rod

Ask the manufacturer

it is really up to them to approve their collector for drainback use. You mentioned all the correct concerns with a collector that can reach 300F or more under stagnation conditions.



In it's simplest form a collector is is some copper tube in an aluminum frame, covered with glass. Newer insulation products that are being tried include foam sheets or injected foam, fleese, cotton, various wool blends, and a vacumn space.



The European solar companies are starting to address the drainback market with complete tank/ collector/ pump station kits.



Check the back issues of www.sunwindenergy.com they have had several articles on drainback products and system reviews.



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