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Old 09-18-20, 12:13 PM   #5
Hong Kong
Join Date: May 2010
Location: Hong Kong
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Originally Posted by SDMCF View Post
I assume you mean horizontal - or actually a little off horizontal to facilitate drainback. If the manifolds were vertical the tubes would be horizontal and I don't think they would work in that orientation.

You should be able to look through the manifold end-to-end before you install it. I would be very surprised if there were a kink in the pipe, and even more surprised if the kink were big enough to cause a problem. I would return a manifold with such a kink.
Even if there were a minor kink I don't think it would be a problem if you have enough fall on the system. I have heard 1" of fall for every 4 ft of run as being good but don't know fist hand if that is correct. Anyway, I believe freezing any water left standing in the system could only cause a problem if, when frozen, it could be over half way up the pipe at the deepest point. Without that I don't see how freezing could split the pipe, which is surely the real concern?

I think you are over-complicating things and in reality there isn't an issue here.

Cold weather is not an issue. You can ignore ambient temperature.

Overcast / low / diffuse light conditions are an issue. You say you are designing around that. Great, I hope you succeed and I will be interested to see your results. Personally I do not know how to do that. In November & December when there is typically heavy cloud cover here my system produces about 2% of the output it does in February & March, even though the temperatures can be 20C or 30C or more higher in November & December.

I agree with that. I guess a lot depends on your local conditions. I need the heat the most when the weather is at its coldest, and around here that does not coincide with when the light is worst. Hence I can get heat when I need it most. I would certainly like to get heat when the skies are overcast but I accept that it has not been possible. If you can show how that can be done I am all ears. Good luck!
Yes, of course you are right, SDMCF, I meant horisontal. Where I have installed systems before, people are scared of drainback because there are stories about how pipes or collectors have been cracked open in frost.

Some also mention how an "open" system will keep adding oxygen to the water, and then the installation will corrode from inside.

I know that it does NOT have to be an open system. Water and air can exist in a closed system. In fact, the air means the expansion vessel can be replaced by the drainback-vessel. In theory, you could even leave the top of the hot water buffer with air, although, a separate vessel is probably better.

Rather than making a lot of mistakes and have to redo the system, I am trying to weed out as many traps before hand as I can. I have gotten it down to a system so simple, that the only heat exchanger will be to extract hot tap/shower water from the hot water buffer. And then possibly from an alternative heat source. Where my biggest system is installed (my own house), the shared district heating water is running all the way out to the radiators in each house, in the original installation.

Anyway, I will keep researching to make the best possible system.

ABout the solar panels working in cold-overcast-low light: I will never be claiming to get more energy out of the light that there is. But even with a loss, the techniques I will be using will work together to enrich the energy there is, into something usable. Combined with other technologies, like seasonal heat storage and radiant floor heating, the plan is obviously to minimise or entirely avoid using a back-up heat source.
Space heating/cooling and water heating by solar, Annual Geo Solar, drainwater heat recovery, Solar PV (to grid), rainwater recovery and more ...
Installing all this in a house from 1980, Copenhagen, Denmark. Living in Hong Kong. Main goal: Developing "Diffuse Light Concentration" technology for solar thermal.
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