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  1. #1
    Join Date
    Jul 2001
    Location
    Cornwood near Plymouth, Devon
    Posts
    205

    Default Hot Water when the calorifier goes cold?????????????

    We have a Moody Eclipse with a Volvo raw-water cooled engine fitted with a calorifier (and immersion heater for shore power); we get reasonably hot water after the engine has been running, but, inevitably, after a few hours the water isn't hot. Given that we have the luxury of a good size shower facility in the heads, I'd like to have a method of generating hot water on demand.

    Our previous boat (Vancouver 32) had a gas heater in the heads, but these seem to have fallen out of favour, presumably for safety reasons; fitting one would probably be slightly awkward given the layout in the heads. I know that some people advocate using an inverter connected to the immersion heater, but I'm wondering about the drain on the batteries ( 2x 110ah for domestic use).

    The thought occurred to me that using a small petrol generator wired into the immersion heater might be an answer, but I'm not sure what output would be needed or indeed how long it might need to run - I'm sure I'm not alone in being very irritated by boats running generators for hours in quite anchorages.


    Any thoughts/experiences would be useful - thanks.

  2. #2
    Join Date
    Mar 2005
    Location
    Hants/Lozère
    Posts
    4,416

    Default Re: Hot Water when the calorifier goes cold?????????????

    Get used to cold showers?

  3. #3
    Join Date
    Oct 2004
    Location
    I know how fast I'm going, but not where I am
    Posts
    6,944

    Default Re: Hot Water when the calorifier goes cold?????????????

    Electric heater off an inverter powered by the batteries is a non starter. Heating water requires far too much energy. A 2 kilowatt generator will heat enough water for a shower in 45 minutes or so.

  4. #4
    Join Date
    Jun 2013
    Posts
    3,346

    Default Re: Hot Water when the calorifier goes cold?????????????

    Depends on the size of your immersion. Last boat had an 800w one and I used a 1kw genny to heat water. Current boat has 1500w immersion and genny is now no good. Choice is bigger genny or smaller immersion.
    If found in the Brexit forum, please return to the real world.

  5. #5
    Join Date
    Jun 2001
    Location
    UK East Coast
    Posts
    1,779

    Default Re: Hot Water when the calorifier goes cold?????????????

    Quote Originally Posted by Gazza View Post
    We have a Moody Eclipse with a Volvo raw-water cooled engine fitted with a calorifier (and immersion heater for shore power); we get reasonably hot water after the engine has been running, but, inevitably, after a few hours the water isn't hot. Given that we have the luxury of a good size shower facility in the heads, I'd like to have a method of generating hot water on demand.

    Our previous boat (Vancouver 32) had a gas heater in the heads, but these seem to have fallen out of favour, presumably for safety reasons; fitting one would probably be slightly awkward given the layout in the heads. I know that some people advocate using an inverter connected to the immersion heater, but I'm wondering about the drain on the batteries ( 2x 110ah for domestic use).

    The thought occurred to me that using a small petrol generator wired into the immersion heater might be an answer, but I'm not sure what output would be needed or indeed how long it might need to run - I'm sure I'm not alone in being very irritated by boats running generators for hours in quite anchorages.


    Any thoughts/experiences would be useful - thanks.
    My calorifier now gives warm enough water for a shower the following morning after fitting some decent insulation.

    Www.solocoastalsailing.co.uk
    Last edited by Plum; 26-06-19 at 21:22.

  6. #6
    Join Date
    Oct 2014
    Location
    London
    Posts
    132

    Default Re: Hot Water when the calorifier goes cold?????????????

    Quote Originally Posted by Gazza View Post
    We have a Moody Eclipse with a Volvo raw-water cooled engine fitted with a calorifier (and immersion heater for shore power); we get reasonably hot water after the engine has been running, but, inevitably, after a few hours the water isn't hot. Given that we have the luxury of a good size shower facility in the heads, I'd like to have a method of generating hot water on demand.

    Our previous boat (Vancouver 32) had a gas heater in the heads, but these seem to have fallen out of favour, presumably for safety reasons; fitting one would probably be slightly awkward given the layout in the heads. I know that some people advocate using an inverter connected to the immersion heater, but I'm wondering about the drain on the batteries ( 2x 110ah for domestic use).

    The thought occurred to me that using a small petrol generator wired into the immersion heater might be an answer, but I'm not sure what output would be needed or indeed how long it might need to run - I'm sure I'm not alone in being very irritated by boats running generators for hours in quite anchorages.


    Any thoughts/experiences would be useful - thanks.
    Eberpacher, Webasto and Planer manufacture diesel water heaters. The first two are expensive, the Planar's are cheaper although perhaps threatened by much cheaper Chinese units. Coolant passes thru the heater and either goes thru a coil in a colorifier or it can go thru a small heat exchanger which promises something akin to hot water on demand - but be aware these heaters do take 5 or so minutes to warm up properly.
    I have a Planar 4kw feeding into one of two coils of a 30L calorfier. Not without issues plumbing all this in and units are a bit noisy and of course the glow plugs and pumps use electricity.
    In a way I regret not getting a bigger unit and using it for space heating as well as for hot water.
    The planar units are about 5-6 hundred pounds and you will need some radiator pipe, some valves etc and a dual coil tank (if you still want to take advantage of the engine heat.
    From your description of your battery bank I do not think it is possible to heat sufficient water using them.

  7. #7
    Join Date
    Apr 2005
    Location
    Shropshire
    Posts
    8,829

    Default Re: Hot Water when the calorifier goes cold?????????????

    Showers on a boat? What's wrong with wet wipes? (Except plastic content of course)

  8. #8
    Join Date
    Mar 2019
    Posts
    8

    Default Re: Hot Water when the calorifier goes cold?????????????

    - Check the isolation of your hot water tank. Ours keep the water warm enough for almost 24 hours. (Make sure no one uses hot water when washing their hands etc... Most don't realise they spent hot water if they use the hot side of the tap for a few seconds.)

    - 1200 Watt heating element heats our tank to warm in 10 minutes, hot enough for shower in 15 minutes. (with 2000 Watt inverter) Our 600 Watt solar panels recharges in a few ours. Still, we use this option rarely.

  9. #9
    Join Date
    May 2007
    Location
    Cambridge, UK
    Posts
    6,042

    Default Re: Hot Water when the calorifier goes cold?????????????

    A 1kw immersion heater will draw about 83 amps at 12 volts (watts = volts times amps). WIth 2 110Ah batteries, you're going to use all the available capacity to run the immersion heater for an hour, presumng the batteries are fully charged to start with.

    The specific heat of water is 4.16 kiloJoules per Kilogram - that is, it requires 4160 joules to raise the temperature of a kilogram of water by 1 degree C. Therefore, to raise the temperature of (say) 20 kg by (say) 30 degrees C will take 4160x20X30 - that is, 2,496,000‬ Joules. A watt is a Joule per second, to a 1kw heater will take 2,496 seconds (41.6 minutes) to heat the water by 30 degrees. SO, heating a tank of water is going to totally flatten your batteries, and that's assuming the tank is perfectly insulated - which, of course, it isn't.

    In other words, heating water from your battery bank is going to use all your available battery capacity to heat one tank of water. The only viable way of doing that would be to run the engine while operating the immersion heater - which rather defeats the object of the exercise!

  10. #10
    Join Date
    Jul 2004
    Location
    west yorks/Greece ionian
    Posts
    285

    Default Re: Hot Water when the calorifier goes cold?????????????

    Our hot water tank is 40 litres, very well insulated and fitted with a 1200 watt immersion heater, to get a full tank of hot water takes ages if we are at anchor using main engine, If we want quick hot water I have a 2kw Honda which heats tank in about 20 mins . I'm very aware of keeping use to a minimum to avoid annoying others and also place the genny on a rubber Matt to keep noise down, it's certainly not quiet but 15-20 mins and all is done .....plus a few further minutes if wife wants hairdryer on .....,! Iv rowed away from the boat to check and it doesn't seem bad and probably better than main engine churning away for much longer. Easiest solution would be leave the wife at home !

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