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  1. #21
    Join Date
    Nov 2007
    Posts
    108

    Default Re: 12 volt water heating ?

    Thanks for that-- seems to add up ; I had v. roughly worked out , for the wife (who has done physics , at least to o level-- astonishingly , my grammar school in the early 60`s channelled biologists into german , no french , and no physics even o level) , that a year of solar into our cylinder could approximate a day of immerser , from your earlier figures ; we never use either immerser , of course . J

  2. #22
    Join Date
    Jan 2003
    Posts
    889

    Default Re: 12 volt water heating ?

    Wow, what did I start here - from August 2006 till now and still rearing its head !!

    I shall think more carefully before asking questions in the future

    [img]/forums/images/graemlins/laugh.gif[/img]
    I used to be indecisive, but now I'm not so sure...

  3. #23
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
    Join Date
    Jul 2002
    Posts
    32,044

    Default Re: 12 volt water heating ?

    from August 2006 till now
    Is it a record? The longest running thread?
    Last edited by VicS; 21-02-12 at 21:01.
    Sea Wych Owners Association: www.Seawych.org

  4. #24
    Join Date
    Feb 2012
    Posts
    2

    Default Yes you can!

    And it's easy too.

    I've got a 1980 Morgan 46, 10cu ft fridge dropped to 8cu ft with extra insulation and then installed a WONDERFUL seafrost fridge system with a freezer box. the amphr consumption on this system is tiny. We liveaboard in the caribbean with 5 people on board (3 sons) - meaning the fridge gets opened and loaded with new stuff often, and we still calculate only 50-60 amp hrs per day.

    On the arch/davits on the stern I have 3 - 135w kyoceras charging the 6 - 12v trojans via 2 different charge controller (and this is important, the charge controllers have a direct supply line for loads you want to run only via solar and never to draw from the batteries. Most mornings my batteries are full by 9am, covering the fridge, fans, lights (all LED lights now), tv and laptop charging.

    Once the batteries have filled from the previous nights use, we start the water maker, also run from the batteries via inverter.

    After all this is done, we still have 1/2 the day with the solar panels doing nothing!

    So, got a 200w 12v heater element. simply screw out the 110v element that is worthless as we're NEVER on shore power, and haven't run the generator in 2 years, then screw in the 12v element and connect the supply wiring (using the existing thermostat to the supply feed on one of the charge controllers). i also put a simple toggle switch in line so it doesn't come on until all other loads are satisfied.

    This runs the water heater (yes, slowly, and never scalding hot but nice and warm for the morning shower!) while still leaving one panel via it's own charge controller keeping the batteries topped up.

    Why can i make it work when others say not?

    1. Efficiency! Start with your refrigeration !INSULATE! and get one of the super efficient 12v danfoss systems!

    2. Efficiency! Brushless dc fans are the only ones permitted.

    3. Efficiency! Every light in the boat is LED and my wife loves them! (including nav lights, spreader and arch mounted deck lights, look for the led spotlights made for sportfisher cockpits, great lights and almost no draw)

    3. BIGGER is better on your battery bank, not just to last thru a cloudy week but because the lower the draw rate the better batteries perform and the longer they last as they don't cycle deeply. (most mornings we wake up to batteries saying 12.5 - 12.6v).

    Yes, it took a few years to get the system as we like it now, but there is still more to go, namely:
    - remove the 120amp alternator from the engine and go back to the stock 65 amp.
    - remove the old shore power battery chargers
    - get rid of the generator

  5. #25
    Join Date
    Jan 2003
    Posts
    889

    Default

    Quote Originally Posted by DrBruce View Post
    And it's easy too.

    I've got a 1980 Morgan 46, 10cu ft fridge dropped to 8cu ft with extra insulation and then installed a WONDERFUL seafrost fridge system with a freezer box. the amphr consumption on this system is tiny. We liveaboard in the caribbean with 5 people on board (3 sons) - meaning the fridge gets opened and loaded with new stuff often, and we still calculate only 50-60 amp hrs per day.

    On the arch/davits on the stern I have 3 - 135w kyoceras charging the 6 - 12v trojans via 2 different charge controller (and this is important, the charge controllers have a direct supply line for loads you want to run only via solar and never to draw from the batteries. Most mornings my batteries are full by 9am, covering the fridge, fans, lights (all LED lights now), tv and laptop charging.

    Once the batteries have filled from the previous nights use, we start the water maker, also run from the batteries via inverter.

    After all this is done, we still have 1/2 the day with the solar panels doing nothing!

    So, got a 200w 12v heater element. simply screw out the 110v element that is worthless as we're NEVER on shore power, and haven't run the generator in 2 years, then screw in the 12v element and connect the supply wiring (using the existing thermostat to the supply feed on one of the charge controllers). i also put a simple toggle switch in line so it doesn't come on until all other loads are satisfied.

    This runs the water heater (yes, slowly, and never scalding hot but nice and warm for the morning shower!) while still leaving one panel via it's own charge controller keeping the batteries topped up.

    Why can i make it work when others say not?

    1. Efficiency! Start with your refrigeration !INSULATE! and get one of the super efficient 12v danfoss systems!

    2. Efficiency! Brushless dc fans are the only ones permitted.

    3. Efficiency! Every light in the boat is LED and my wife loves them! (including nav lights, spreader and arch mounted deck lights, look for the led spotlights made for sportfisher cockpits, great lights and almost no draw)

    3. BIGGER is better on your battery bank, not just to last thru a cloudy week but because the lower the draw rate the better batteries perform and the longer they last as they don't cycle deeply. (most mornings we wake up to batteries saying 12.5 - 12.6v).

    Yes, it took a few years to get the system as we like it now, but there is still more to go, namely:
    - remove the 120amp alternator from the engine and go back to the stock 65 amp.
    - remove the old shore power battery chargers
    - get rid of the generator


    Thanks for the reply. Even though its a bit late

    Just to make sure I get this right -the solar panel goes to the controller and then to the 12v immersion -yes?

    Do you use the battery terminals on the controller or the load output terminals?

    So you could do this with the wind generator as well (via the controller)
    I used to be indecisive, but now I'm not so sure...

  6. #26
    Join Date
    Jan 2003
    Posts
    889

    Default

    Quote Originally Posted by VicS View Post
    [ QUOTE ]
    from August 2006 till now

    [/ QUOTE ] Is it a record? The longest running thread?



    It must be now, unless someone can prove otherwise.


    And before you ask I didnt pay him to put hte post up!


    I used to be indecisive, but now I'm not so sure...

  7. #27
    A1Sailor's Avatar
    A1Sailor is offline Registered User
    Location : At sea - in Clyde/Caledonia
    Join Date
    Jul 2004
    Posts
    7,845

    Default

    Why not cut a hole in the deck above the hot water tank? When the sun comes out it'll warm up the water. Simples!

  8. #28
    Join Date
    Jan 2003
    Posts
    889

    Default

    Quote Originally Posted by A1Sailor View Post
    Why not cut a hole in the deck above the hot water tank? When the sun comes out it'll warm up the water. Simples!


    I can tell your definately from that Green lobby!
    I used to be indecisive, but now I'm not so sure...

  9. #29
    Join Date
    Feb 2012
    Posts
    2

    Default Clarification

    the solar charge controllers joins the panels to the batteries, doing their usual job of limiting voltage and preventing night drainage back to the panels, but also have a direct power take off which you can use to supply 12v DC loads which you want to run ONLY when the panels are working.

    I have friends with smaller RO watermakers which they hook directly to the charge controllers like this and they leave the 1-2 gph watermaker running all day.

    I toyed with the idea of running my larger watermaker like this but the start up draw was too great for the pump, so run it from the batteries. I am still planning a timer system so it comes on each day for 2 hours without me needing to remember to flip the switch.

    Originally I had planned to build a solar water heater receiver mounted on the arch along with the PV panels, and then use a small 12v pump to recirculate the fluid to our water heater tank by bypassing the engine/hot water exchanger system, and for that the direct draw from the charge controller would have been perfect too. If I didn't have such excess electric production, I still would have gone this route to get hot water, because for the last 2 years, running the engine to make hot water was the only reason we ran the motor other than for propulsion.

    One caveat to my other posting, we live in the caribbean, so the water in the hull tanks average 75F to start with, and we've set the thermostat on the heater to shut off at only 100F, so we really didn't need much heating effect, certainly as compared to some of you chilly weather boaters!

    If we end up cruising into colder climes, I'll go back to my idea of a solar receiver.

  10. #30
    Join Date
    Sep 2007
    Posts
    2,079

    Default

    Quote Originally Posted by wizard View Post
    Thanks for the theory VicS that will make the calculations easier.

    I was thinking of getting a 12v element from somewhere (yet to be found) and plumb it into the existing calorifier which is already insulated.

    There used to be a heater element for cars years ago to put into the bottom hose leading to the radiator to both stop the water freezing and to warm up the water to make the engine start in the depths of winter. Some worked off the battery and some with mains transformers - but with modern cars all this sort of thing has become redundant.

    Still I shall keep looking...
    Just e bay it-plenty available-in a renewable home system often forgotten that a very good spare energy store is the hot water cylinder-so when you are producing spare energy and batteries are full you dump it into the calorifyer via the 12v immersion-my calorifier has a standard size immersion heater plug blank.

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