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  • FIRST POST
    • Wobblydeb
    • By Wobblydeb 16th Apr 18, 11:15 AM
    • 988Posts
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    Wobblydeb
    How much hot water is in my tank?
    • #1
    • 16th Apr 18, 11:15 AM
    How much hot water is in my tank? 16th Apr 18 at 11:15 AM
    I've done some googling and not come up with much on this topic, so hoping you knowledgeable people can help :-)

    We have an open vented system with a hot water cylinder.

    How do I tell how much (and how hot) the water is in the cylinder? I am heating with a mixture of gas and solar/immersion at the moment. I would like to reduce the gas, but have no way of knowing whether we've got enough hot water for the evening.....

    Are there devices to tell you this?
    I've got a plan so cunning you could put a tail on it and call it a weasel.
Page 1
    • silverwhistle
    • By silverwhistle 16th Apr 18, 11:39 AM
    • 2,085 Posts
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    silverwhistle
    • #2
    • 16th Apr 18, 11:39 AM
    • #2
    • 16th Apr 18, 11:39 AM
    Measure it, make an allowance for the insulation, and if I remember my maths from 50 years ago the volume should be pi*r2*h. You'll arrive at an approximate number and as I believe tanks tend to be a number of standard sizes choose the nearest!
    • Wobblydeb
    • By Wobblydeb 16th Apr 18, 12:14 PM
    • 988 Posts
    • 1,458 Thanks
    Wobblydeb
    • #3
    • 16th Apr 18, 12:14 PM
    • #3
    • 16th Apr 18, 12:14 PM
    Ooops sorry I wasn't very clear. I know that it is a 114 litre tank - what I don't know is what temperature the water is at.....

    i.e. At 6pm do I have enough hot water for a shower or will it run out half way through?
    I've got a plan so cunning you could put a tail on it and call it a weasel.
    • EricMears
    • By EricMears 16th Apr 18, 1:08 PM
    • 2,348 Posts
    • 4,112 Thanks
    EricMears
    • #4
    • 16th Apr 18, 1:08 PM
    • #4
    • 16th Apr 18, 1:08 PM
    - what I don't know is what temperature the water is at.....

    i.e. At 6pm do I have enough hot water for a shower or will it run out half way through?
    Originally posted by Wobblydeb
    Since you said earlier "I am heating with a mixture of gas and solar/immersion at the moment" then you don't really need to know.

    Just make sure that the immersion setpoint temperature is higher than the gas boiler's and your shower shouldn't run cold halfway through.

    You wouldn't really put off having a shower when you wanted just because there wasn't enough 'free' hot water would you ?
    N Derbyshire.
    4kwp S Facing 17.5deg slope (dormer roof).
    • Ectophile
    • By Ectophile 16th Apr 18, 10:00 PM
    • 3,290 Posts
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    Ectophile
    • #5
    • 16th Apr 18, 10:00 PM
    • #5
    • 16th Apr 18, 10:00 PM
    It sounds to me like the best option would be to set the timer for the gas boiler to come on in the early evening, when the solar is done for the day. Make sure the thermostats are set appropriately, and the gas boiler shouldn't use much gas if the water is already up to temperature.

    I've never heard of a hot water tank thermometer. If you can tell by touching the tank, then it's not insulated properly.
    If it sticks, force it.
    If it breaks, well it wasn't working right anyway.
    • Wobblydeb
    • By Wobblydeb 16th Apr 18, 10:24 PM
    • 988 Posts
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    Wobblydeb
    • #6
    • 16th Apr 18, 10:24 PM
    • #6
    • 16th Apr 18, 10:24 PM
    You wouldn't really put off having a shower when you wanted just because there wasn't enough 'free' hot water would you ?
    Originally posted by EricMears
    No, if there is insufficient hot water, I would run the gas boiler for 30 mins......

    What I don't know is whether there is enough hot water or not, and I don't want to waste gas uneccessarily.

    It sounds to me like the best option would be to set the timer for the gas boiler to come on in the early evening, when the solar is done for the day. Make sure the thermostats are set appropriately, and the gas boiler shouldn't use much gas if the water is already up to temperature.
    Originally posted by Ectophile
    I do this in the morning, to ensure we can get our showers. At the moment, I don't bother in the evening as we don't use much hot water. I may have to run the gas when we have guests just to ensure there is enough hot water. Just seems a shame there is no way of knowing and hence saving gas if it is not needed
    I've got a plan so cunning you could put a tail on it and call it a weasel.
    • Tom99
    • By Tom99 16th Apr 18, 11:46 PM
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    Tom99
    • #7
    • 16th Apr 18, 11:46 PM
    • #7
    • 16th Apr 18, 11:46 PM
    Is there a thermostat strapped to the side of the hot water tank which controls the gas boiler and if so does it click on/off as you turn the temp up/down?
    • silverwhistle
    • By silverwhistle 17th Apr 18, 3:58 PM
    • 2,085 Posts
    • 2,864 Thanks
    silverwhistle
    • #8
    • 17th Apr 18, 3:58 PM
    • #8
    • 17th Apr 18, 3:58 PM
    Whoops, missed your point, and I have to say I have no idea how many litres are in my tank! But I do have solar panels and a diverter, which passes surplus power to the immersion heater. I've raised the thermostat on the tank from the normal setting to store more energy and both the gas heating (if I put it on) and the solar switch off if the tank is hot enough.

    I don't use the boiler on timer, just switch it on manually if I see there hasn't been much solar saved. You'll probably get a feel for things, like I can assess roughly how much I'm generating by looking out the window and observing the light quality (and then check the monitor on my tablet to make sure).
    • Common Man
    • By Common Man 17th Apr 18, 4:28 PM
    • 13 Posts
    • 26 Thanks
    Common Man
    • #9
    • 17th Apr 18, 4:28 PM
    • #9
    • 17th Apr 18, 4:28 PM
    Small battery digital thermometer with 1.45 metre lead on E Bay for under 3.
    Make a small hole with a pencil in the tank insulation,pop the probe in making sure it contacts the metal tank. I have mine about 1/3
    of way down .If it reads over 52C I know there is enough hot water for 2 showers.At the moment it is reading 65C. Perhaps spring really is here now.
    • Wobblydeb
    • By Wobblydeb 17th Apr 18, 8:41 PM
    • 988 Posts
    • 1,458 Thanks
    Wobblydeb
    I've raised the thermostat on the tank from the normal setting to store more energy and both the gas heating (if I put it on) and the solar switch off if the tank is hot enough.
    Originally posted by silverwhistle
    What a good idea - I hadn't thought about increasing the temperature so that more solar was used up. What temperature do you have it set at? I'm a bit worried about scalding risk....

    Small battery digital thermometer with 1.45 metre lead on E Bay for under 3.
    Make a small hole with a pencil in the tank insulation,pop the probe in making sure it contacts the metal tank. I have mine about 1/3
    of way down .If it reads over 52C I know there is enough hot water for 2 showers.At the moment it is reading 65C. Perhaps spring really is here now.
    Originally posted by Common Man
    Fab!!! Thank you - I knew I couldn't be the first person to want to know this
    I've got a plan so cunning you could put a tail on it and call it a weasel.
    • silverwhistle
    • By silverwhistle 18th Apr 18, 1:00 AM
    • 2,085 Posts
    • 2,864 Thanks
    silverwhistle
    What a good idea - I hadn't thought about increasing the temperature so that more solar was used up. What temperature do you have it set at? I'm a bit worried about scalding risk....
    Originally posted by Wobblydeb
    To be honest I don't remember and it's too late to check. Maybe an extra 10#? It can get _very_ hot so scalding could be a danger in the absence of common sense. I've an electric shower so the hot water is used for washing up and baths. With a shower you wouldn't want someone else to turn the cold tap on, I imagine..
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