Which Solar hot water system?

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Re: Which Solar hot water system?

Postby Gordon-Loomberah » Sun Feb 18, 2018 1:12 pm

gpigeon wrote:Gordon.....how is the "Runonsun" unit going after all these years?



Hi Bill it is still going very well, no sign of any leaks or corrosion. I never did get around to automating the covering of the tubes on the house hot water system, I just ~1/3 cover the tube array with 90% shade cloth in sunny weather between about Sept and April, which around here basically means it is 1/3 covered for 8 months of the year, and rarely removed, as more than day or 2 of cloud doesn't occur very often.
I can add heat for showers from the larger hydronics array system via a heat exchanger if required. I haven't yet done anything with the wax I bought as a phase change heat store, but still have plans to do it, it's just not a priority.
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Re: Which Solar hot water system?

Postby gpigeon » Mon Feb 19, 2018 7:10 am

australsolarier wrote:
as for covering up the heat pipes. this also is a non issue. it looks great on paper and in the planning phase. in practice however, it has a lot of problems. it is mechanical and can fail. there is a problem with wind. and it is costly.
i followed fora where people built large systems for house heating. not one of them built something covering the solar panels. but many were thinking about it.


Yes "australsolarier".....you are right about the mechanical = moving parts = potential problems!!!! I deliberately chose the close coupled system because there are no moving parts (except for PRT valves) and now I am fitting moving bits and pieces! Just like Gordon, I may end up being one of those just thinking about it!

My neighbour has a "RunonSun" unit but NOT the close coupled type and he still has to manually cover the tubes to prevent overheating. Maybe he has a problem with one of the components(pump, etc.) I am not sure how, in the pumped system, the temp is controlled on a very hot day.

Re. galvanic corrosion (dissimilar metals).....my old "Beasley" flat panel system was still operating ok after 30 yrs service (using ground/spring/rain water) when I recently sold the house. It had a SS316 close coupled tank and NO sacrificial anode. This new RunonSun unit has a SS316 tank but with an anode. I understand from the suppliers that is because of the copper inserts in contact with the SS shell.

Gordon, do you regularly check/change the anode?

Time will tell!
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Re: Which Solar hot water system?

Postby Gordon-Loomberah » Mon Feb 19, 2018 9:09 am

gpigeon wrote:Gordon, do you regularly check/change the anode?


I haven't checked it since I've had it, so whether there has been any sacrificing, of Mg or even of goats! going on in my tank, I dont know ;)
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Re: Which Solar hot water system?

Postby gpigeon » Sun Sep 02, 2018 7:43 am

Gordon-Loomberah wrote:
gpigeon wrote:Gordon.....how is the "Runonsun" unit going after all these years?

Hi Bill it is still going very well, no sign of any leaks or corrosion. I never did get around to automating the covering of the tubes on the house hot water system, I just ~1/3 cover the tube array with 90% shade cloth.... it's just not a priority.


C'mon Gordon...don't let me get ahead of you!!!!
I can now operate the curtain from the verandah. will trial it for a season and then add the remotes/limit switches if all is good.
What a pita job! Up on the roof, very dangerous for old codgers!
I smiled at my neighbours arrg't. when he put the panels at ground level. In hindsight, I should have done the same thing. I had plenty of space and access to the curtain would have been far simpler.
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Re: Which Solar hot water system?

Postby australsolarier » Sun Sep 02, 2018 7:48 am

good job.
remains to be seen how it goes in strong winds.
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Re: Which Solar hot water system?

Postby gpigeon » Mon Nov 05, 2018 7:09 am

australsolarier wrote:good job.
remains to be seen how it goes in strong winds.


No strong winds yet.....We have had 3 consecutive days of 33+ deg and on the first day the releif valve opened at 88 deg. The following day I wound the curtain up to about 60% cover and the temp has only gone to 77deg.
Not as much affect on the temp as I had expected!!! It remains to be seen how it will go when the ambient temp is 40+ deg. I have used heavy shade cloth but maybe it needs a more opaque cloth.
I still don't have the limit switches fitted so I have to have my wife standing out on the lawn as observer :shock: while I operate the motor from the verandah.
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Re: Which Solar hot water system?

Postby Gordon-Loomberah » Mon Nov 05, 2018 9:17 am

With evacuated tubes the ambient air temp is largely irrelevant- most important is radiation intensity. They can still boil water when the air temp is only 10C if the sky is clear and the sun high enough up!
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Re: Which Solar hot water system?

Postby australsolarier » Mon Nov 05, 2018 1:42 pm

gordon,
as far as the vacuum pipes are concerned you are correct. but there are the circulation pipes, the header, the tank itself. also the temperature of the "cold" water going in.
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Re: Which Solar hot water system?

Postby Gordon-Loomberah » Mon Nov 05, 2018 1:46 pm

Hopefully all those bits are well insulated!
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Re: Which Solar hot water system?

Postby australsolarier » Mon Nov 05, 2018 2:00 pm

yes, as far i am concerned i did insulate them well.

as for the solahart thermosyphon system i also have, the tank is not well insulated at all and loses a lot of energy. in their brochure i remember reading that the flat solar panels deliberately are not well insulated to avoid boiling temperatures. and they are absolutely correct. the sun won't get it to boil. even the thermosyphon to the wood cooking stove will not bring the tank to boil. (the panels act as a cooling device).

in windy weather there is quite a difference in heat harvest between the flat panel and the vacuum pipes. the vacuum pipes seem not to be affected at all. but the flat panels definitively are.
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