Which Solar water heater? - PLEASE HELP URGENT!

Discussion in 'The Sump' started by lIghty, 24 Feb 2010.

  1. lIghty

    lIghty

    Joined:
    3 Nov 2007
    Posts:
    5,053
    Likes Received:
    52
    Location:
    Westville, Durban
    Hi All

    I'm needing to have a solar water heater fitted urgently! As far as I know there are 2 main types available, "Flat Plate type" and "Evacuated Tube type".

    I do understand the differances between the 2, but if someone has knowledge why one is better than the other please shout, I have my thoughts but it would be nice having comfirmation from someone in the industry or someone that has had one fitted.

    Also, if there is companies in the KZN area that you could recommend, preferably one that can offer the Eskom rebate.

    Thanks in advance!
     
  2. AdS Guest




    to hide all adverts.
  3. Hill

    Hill

    Joined:
    8 May 2007
    Posts:
    1,473
    Likes Received:
    3
    Location:
    Auckland
    I looked into solar a few years back.

    Basically the evacuated tube are the most efficient IIRC. More expensive though. With the sunlight in SA either will probably do a good job. The ET will probably be better on cloudy days though as apparently they do not need direct sunlight.
     
  4. Reef Maniac

    Reef Maniac MASA Contributor

    Joined:
    15 May 2007
    Posts:
    2,899
    Likes Received:
    112
    Location:
    Bloemfontein
    I did some research some years ago, before installing my solar water heater... in the end I settled on an evacuated tube system, and have been very happy with it ever since.

    My 20 tube system hears my 200 liter geyser to between 55 C and 85 C. The electrical supply to the geyser is permanently switched off, and we only put it on when it's been raining/totally over-cast for more than a day. The water actually becomes TOO HOT, and in summer I turn 10 of the tubes around, so they do not heat, and let the system run on 10 tubes.

    If you plan to use your existing geyser, I would recommend that you use a hot-water pump to circulate the water from the heat collecter to the geyser - the "solar syphon" does not work very efficiently (although that is true for either type of system...).

    Let me know if you need more advise - I installed my system myself, and learned a lot through trial and error.

    Hennie
     
  5. LuckyFish

    LuckyFish MASA Contributor

    Joined:
    23 Nov 2009
    Posts:
    2,531
    Likes Received:
    103
    Location:
    Cape Town
    I second that in total. I installed many systems in Germany, both types.
    I always prefer the tube system, because they are much more efficient.
    Also, if your roof is not perfectly in the right angle to the sun, the tube will compensate this.

    Also what Hennie had to say about it, no doubt.

    All depends on your roof and your wallet!
     
  6. lIghty

    lIghty Thread Starter

    Joined:
    3 Nov 2007
    Posts:
    5,053
    Likes Received:
    52
    Location:
    Westville, Durban
    thx for you input guys, from what I've heard from alot of the local guys here in KZN is that the ET are too efficient, causing them to over heat and damaging themselves, they have had problems with the glass breaking and seals failing(loss of vacuum). The ET where mainly designed for use in Europe where the climate is much cooler, and hence the extra insulation.... whats your thoughts.
    Posted via Mobile Device
     
  7. Reef Maniac

    Reef Maniac MASA Contributor

    Joined:
    15 May 2007
    Posts:
    2,899
    Likes Received:
    112
    Location:
    Bloemfontein
    Although it is true that they are very efficient, and that they can over heat the system, I suspect that most of these "doom" stories are just sales talk.

    Because of the vacuum in the glass tubes, the glass does not heat up - even when my water temperature is 85°C - 90°C the glass tubes are cold to the touch, so it's pretty unlikely that they would break from the heat... I installed my system in March-April 2008, and so far all the tubes have survived intact :whistling: I did do some "designing" of the system, though, and that could have helped to protect the system from too serious over-heating - here's what i did:

    • I coupled the solar heater to my existing geyser, using a non-return valve and a hot water pump, activated by a daylight switch, to ensure continuous water circulation during the day.
    • The hot water pump is connected to my backup power inverter system, to ensure that the pump does not stop when there is a power outage. This is VERY important, IMHO, to prevent over heating of the system. You can alternatively couple the pump to a solar electric panel, to remove it from the vagaries of the ESKOM grid - I'm planning to do so in the near future...
    • I installed a TP valve (that's Temperature/Pressure valve) at the outlet end of the hot water panel. This valve opens automatically once the temperature exceeds about 95°C or the pressure exceeds it's design limit. This then dumps the hot water into the roof gutter, causing cold water to circulate through the system, rapidly cooling everything off. Once the temperature and/or pressure returns to below the threshold limit, the valve automatically resets, and you're left with a geyser full of luke-warm water as the only "damage".
    • As mentioned in my previous post, I manually turn half of the tubes around every summer. This is a 5 minute job, only needing a screwdriver, but you do have to climb on to the roof, though.
    I am currently playing with the idea of creating some sort of electrically activated system to turn all the tubes. This will seriously improve efficiency, as one could then use something like a programmable stepper motor, coupled to a PC, to rotate the tubes through (say) 120 degrees every day, tracking the sun, and keeping the collector plates perpendicular to the sun. This same system could also be used to "switch off" the solar panel when a pre-set water temperature is reached.
    Personally, I would rather have a system which is running at maximum efficiency, and would definitely recommend the evacuated tube system over the flat panel system.

    Hennie
     
  8. lIghty

    lIghty Thread Starter

    Joined:
    3 Nov 2007
    Posts:
    5,053
    Likes Received:
    52
    Location:
    Westville, Durban
    Thanks for the input, I spoke to 3 guys today that had the ET system, they all had problems with the seals on the vacuum section, perhaps just cheep chinese..... hoever I do agree with you, but for the "average" joe putting relief valves and stepper motors to track the sun could be a bit over the top :lol:

    But please keep us (me at least) updated on that your system, really interesting!
     
  9. Hill

    Hill

    Joined:
    8 May 2007
    Posts:
    1,473
    Likes Received:
    3
    Location:
    Auckland
    There may be some merit to the systems failing due to their high efficiency.

    Hennie mentions how to minimise this risk. I would still go Hennie's way of doing things if you can afford it. I would maybe get it to dump the water into a holding tank. You could then monitor when to turn the tubes.

    The failure could also be due to poor workmanship, but that factor is the same for any installation.
     
  10. Rory

    Rory Admin MASA Contributor

    Joined:
    5 May 2007
    Posts:
    4,850
    Likes Received:
    34
    Location:
    JHB
    I was speaking to someone who installs these things for a living about 2 weeks ago and he said the ET systems are indeed the most efficient but for the south africa sun they are actually too efficient and the water gets too hot. His main concern was for the "geyser" part dying prematurely because the hotter temperatures cause them to fail sooner. I suppose you could mitigate it by ensuring proper circulation with a pump and getting an "oversized" geyser tank part but the main way is as Hennie said that you basically waste some water and let more cold water in. He reckons solahart is the way to go.
     
  11. Reef Maniac

    Reef Maniac MASA Contributor

    Joined:
    15 May 2007
    Posts:
    2,899
    Likes Received:
    112
    Location:
    Bloemfontein
    I wonder which parts that would be? The geyser is normally also protected by a TP valve (I think that's in the building regulations...), and I think that the normal heating element can be set up to about 80°C, so I would guess that everything in the system should be designed for at least that, plus a safety factor.

    It is true that the temperature can easily reach 100°C or even higher within a few minutes on a sunshine summer day IF there is no water circulation. I think many (most?) of the failures & problems (such as loss of vacuum) are caused by this, if/when a power failure causes the hot-water circulation pump to stop. It is for this reason that I have hooked my circulation pump to my emergency inverter supply, and why I previously mentioned that one can connect it to a solar power panel which will keep the pump pumping as long as the sun is shining.

    But 10 minutes twice a year to turn some tubes around is all it takes to make it less efficient, and you gain in the winter.

    Interesting discussion, though - I suppose that I am the guinea pig for these systems - let's hope mine lasts for many more years...

    Hennie
     
    Last edited: 28 Feb 2010
  12. seank

    seank

    Joined:
    24 May 2007
    Posts:
    11,984
    Likes Received:
    119
    Location:
    North of Durban and South of Mozambique
    Lighty, you have a pm
     
  13. mnd123

    mnd123

    Joined:
    5 Mar 2008
    Posts:
    1,753
    Likes Received:
    14
    Location:
    Fourways Gardens
    Very interesting read, thanks chaps
     
  14. TheWaterboy

    TheWaterboy Sponsor

    Joined:
    6 May 2007
    Posts:
    2,117
    Likes Received:
    79
    Location:
    Durban
    i commisioned a top durban based company to install 58 large flat panels to heat water to wash down my father in laws meat factory (wholesaler and manufacturing).......the system cost 530k.............and guess what it still draws 120 amps about 5 hours of a daylight day and 8 hours a night.......
    complete waste of money.........go with the tubular system and stay away from a company that operates out of durban north / umhlanga
     
  15. jacquesb

    jacquesb Retired Moderator

    Joined:
    29 May 2007
    Posts:
    17,868
    Likes Received:
    69
    Location:
    Cape Town
    Hey Marco - just something "off topic" (if lIghty does not mind) - perhaps you can go over and have a look at LikesFish's thread - and answer the question about the RO unit tap fitting that is leaking?

    [EDIT] BTW: What do you mean "still pulls 120 amps of electricity"? Is this system connected to the electrical supply then, that it can PULL electricity from the grid?
     
  16. TheWaterboy

    TheWaterboy Sponsor

    Joined:
    6 May 2007
    Posts:
    2,117
    Likes Received:
    79
    Location:
    Durban
    the system has 3 large hot water storage tanks that are insulated but have a thermostst in each to keep the temp constant........the solar poanels cannot heat the water enough, hence they keep switching on the thermostat at 40 amps ea .

    will try look for the thread and try help em out...shotto
     
  17. TheWaterboy

    TheWaterboy Sponsor

    Joined:
    6 May 2007
    Posts:
    2,117
    Likes Received:
    79
    Location:
    Durban
    i searched for the thread as you requested under his threads started list but to no avail.
    could you find it and pm me the link.....cool:thumbup:
     
  18. jacquesb

    jacquesb Retired Moderator

    Joined:
    29 May 2007
    Posts:
    17,868
    Likes Received:
    69
    Location:
    Cape Town
    Thanks Marco - for the explanation, and the willingness to help. It seems that he got sorted!
     
Recent Posts

Loading...
Similar Threads - Solar water heater Forum Date
Water Feautures on SPECIAL! Includes solar charging pad and pumps. WAS R995 NOW... JungleAquatics.NET BLOG 19 Aug 2014
[wtd] 2 X 39w or 2 X 54w SOLARMAX T5 units tme know. Wanted 3 May 2016
Solar power Power cuts 7 Mar 2015
[wtd] Solarmax FlexiLed system Wanted 6 Apr 2014
NEW Solar Fish and Pet Feeders available from our online shop www.aquaria.co.za/... JungleAquatics.NET BLOG 22 Nov 2012
solarmax led units Lighting 30 Mar 2012
Solarmax LED upgrade Lighting 29 Mar 2012