Viewing 9 posts - 1 through 9 (of 9 total)
  • Maximising free hot water from solar with an I boost and hot water tank
  • damascus
    Free Member

    Hi,

    I’ve had solar panels and an I boost for a while now, so far I think I’ve saved 6000kw.  Last year I replaced a 30 year old hot water tank that had a leak that couldn’t be fixed.

    I specced a larger water tank and a titanium immersion heater to make the most of the solar panels. I generate enough hot water between March and November to not use the boiler.

    Only problem is my new water tank uses more kW and doesn’t heat as much water as before.

    I used to get a bath and a shower, now I only get enough for a bath.  I’ve lived with it to now but with the gas and electric prices increasing its cost effective to look at sorting it.

    After a bit of googling it suggests that the immersion heater rod may be too short and not heating the water all the way down. I found an article on the I boost website that suggested installing a de stratification pump to circulate the water so the hole tank is warmed.

    Any advice on how to improve this is appreciated.

    Thanks

    trail_rat
    Free Member

    Sounds like you have got too big a tank for the availible excess power and the tanks not getting to temperature to me…..

    Where as before the whole tank was at a high temperature you could mix it with cold to your desired temp so acts like a considerably larger tank.

    Your new tanks perhaps not getting hot enough.

    A solar thermal array in tandem if you have space and a spare coil int he tank would be a worth addition assuming you are not willing to live with less water or pay for more leccy….

    goldfish24
    Full Member

    You’ve more or less answered your own question there. Only variable you haven’t mentioned is the immersion thermostat setting. Increasing this will increase energy storage and effective hot water capacity. Downsides are potentially scalding hot water, potential to exceed rating of connected equipment (I’m thinking shower pumps that are usually only happy up to 65c), and increased heat loss.

    I’d start by checking the immersion length and checking the water temperature at the outlet to consider thermostat adjustments.

    goldfish24
    Full Member

    I’ve made the opposite assumption to trailrat in my thermostat argument above, either of us could be right. To be clear:

    Trailrat: sun runs out before tank reaches set temperature.
    Goldfish: tank reaches set temperature before sun runs out.

    You’ll have to make some measurements and observations to figure out which is happening.

    damascus
    Free Member

    The cylinder is only about 20 litres bigger, which isn’t a great deal. Its 140 litres in total so not huge.

    The i boost stops when it thinks the cylinder is hot. This can sometimes be around 10am. Once it says “hot” it doesn’t warm it anymore. If I then have a shower the I boost charges the cyclinder again.

    Even if a bath is 60 litres that’s less than half a tank.

    I’ve currently got the heat setting on full. Any hotter and it would burn!

    I think because the immersion heater isn’t very long it doesn’t warm the water all the way down. See the below article from I boost. Its a link to a download so feel free to Google solar I boost tips instead.

    https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.marlec.co.uk/wp-content/uploads/2014/03/Maximising-the-Benefit-of-your-Solar-iBoost.pdf&ved=2ahUKEwjI4tCjour5AhW1SkEAHUuHAy8QFnoECAUQBg&usg=AOvVaw0syplTbffrZr5aLuZDRgix

    steveb
    Full Member

    More information on the tank required!
    Capacity?
    Immersion position (top or side)?
    If top how far down the tank does it reach, if side where is it on the tank? Sometimes immersions are positioned for a quick boost just to the upper part of the tank.
    Ideally iboost runs with 2 immersions, one about mid height, one at the bottom.
    You can max out there Immersion thermostats for maximum energy storage, but then fit a thermo blending valve at the outlet, to give a safe water temperature.

    damascus
    Free Member

    It’s a 1050×450 stainless Steel cylinder and I think it’s only got one immersion at the top. With hindsight I should have made sure it had a 2nd one.

    steveb
    Full Member

    Very much sounds like a short, quick boost for one bath heater. You can get 36″ elements that would be better suited to solar harvesting.

    5 years ago I couldn’t find a 300 litre, unvented, indirect, 2 Immersion tank, so I had one custom made! Such things do exist off the shelf now.

    damascus
    Free Member

    @steveb how do I tell what length mine is? Will the immersion have a lable that gives me all the info?

    I’ll check when I get home. Thanks

Viewing 9 posts - 1 through 9 (of 9 total)

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