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Thread: Solar Geyser Performance?

  1. #16
    Super Grandmaster
    Join Date
    Aug 2008
    Cape Town
    Blog Entries


    Quote Originally Posted by Broadcom View Post
    Actually, the reason for having it at least 300mm below the tank is so that REVERSE thermosyphon will not take place when the temperature differential is reversed ( i.e. at night hot water flowing into the collector and cooling )

    @Linuxgal: Thermosyphon systems are very tricky to plumb. You have to understand the principle, otherwise it won't work. If it has been plumbed correctly, it could be that you have an air lock somewhere in the system preventing the syphon action. There might be a bleed valve or tap at the top of the panel for this.

    Yes, just spoke to my plumber about this and he said same thing. So bleed the system, same as you do motor-car brakes. He also calls every 2 years and flushes it out, gets rid of sediment, etc
    Things won are done; joy's soul lies in the doing

  2. #17


    Thanks, this is the kind of info I need. Will be up on the roof in the morning with tape measure. The installer claims he topped up the glycol and pressure tested the system, so presumably there is no air lock. We have decided to bypass him and get in someone from his HQ.

    @Chrisc4290: Cape Town is 33S and therefore your panel inclination is within 9 deg of latitude - more optimal than ours which is 19 deg from latitude.

  3. #18


    Some technical feedback for those who replied to my thread.
    According to the technician from the distributor's HQ, the optimum angle for thermosyphon is 29 degrees from the horizontal. Above 50 degrees, thermosyphon will not work.
    We had the offending panel moved to our main house roof which is 30 degrees, and the water temperature has improved although it is also getting more sun.
    Cynically, it turns out that the flat roof installation with 45 deg frame was pushed on us by the installer to make life easier for him.

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