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Gas Boiler not heating the copper cylinder as hot as it used to - suggestions?

  • 04-12-2018 4:01pm
    #1
    MiketheMechanic
    Registered Users, Registered Users 2 Posts: 903 ✭✭✭


    I have a gas-fired central heating system.
    Baxi Solo 3 Boiler driving 12 rads.

    My copper cylinder/hot tank has an Immersion heater (bath/sink) as well as the coil (calorifier?) with hot water from the boiler.
    (see attached pic)

    In summer, I can turn off the zone for the rads using a switch near the boiler. This allows the boiler to just heat the hot tank.
    It does a good job - very hot tankful of water, even when the boiler only comes on for a few 30 minute segments during the day/night.

    In winter the boiler drives both the rads and the hot tank.
    Rads get fine and hot and heat the house correctly.
    However recently I've noticed that the hot tank does not get very hot at all - no matter how long the heating is left on for.
    Certainly warmer than lukewarm, but not as hot as I'd like it.
    I'm having to top it up by running the immersion for 15-20 minutes.
    I don't recall having this issue in the winter before.

    Is there anything I should check or tweak before calling a plumber?
    There's a return valve in the hot press that comes from the coil in the tank I think.
    I assume this should be fully opened to allow maximum flow of hot water to/from the boiler?

    There's also a small green Wilo pump next to my boiler (circulating pump?)
    It has 3 speed settings - it's on 3 - the highest flow rate. I assume this is correct.

    Anything else to check?

    Thanks,
    MtM


Comments

  • #2
    agusta
    Closed Accounts Posts: 1,590 ✭✭✭agusta


    The balance valve coming off cylinder coil is normally 1 1/2 revolutions open from the closed position.What position is your balance valve from the closed position approx


  • #3
    MiketheMechanic
    Registered Users, Registered Users 2 Posts: 903 ✭✭✭MiketheMechanic


    agusta wrote: »
    The balance valve coming off cylinder coil is normally 1 1/2 revolutions open from the closed position.What position is your balance valve from the closed position approx


    Thanks augusta

    It's fully open - I figured it should be open to allow the hot water to circulate through the coil and heat the tank - and if it's closed the boiler does not heat the tank.
    Maybe that's the problem and my thinking is flawed :o


    MtM


  • #4
    agusta
    Closed Accounts Posts: 1,590 ✭✭✭agusta


    If the balance valve is fully open,the heat from the boiler should pretty much go to the cylinder first.Does it heat ok when the hot water is on only


  • #5
    MiketheMechanic
    Registered Users, Registered Users 2 Posts: 903 ✭✭✭MiketheMechanic


    agusta wrote: »
    If the balance valve is fully open,the heat from the boiler should pretty much go to the cylinder first.Does it heat ok when the hot water is on only


    Yes, in the summer, the rads are zoned off, the boiler only heats the cylinder via the coil - and does a good job.


    What might this scenario suggest?


  • #6
    agusta
    Closed Accounts Posts: 1,590 ✭✭✭agusta


    you could test the hot water zone in its own and see what you get.things can change since the summer.is it a pressurized system or do you have a small tank in the attic


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  • #7
    John.G
    Registered Users, Registered Users 2 Posts: 3,561 ✭✭✭John.G


    MiketheMechanic wrote: »
    Yes, in the summer, the rads are zoned off, the boiler only heats the cylinder via the coil - and does a good job.


    What might this scenario suggest?

    You seem to be saying that the water is all ways circulating through the cylinder coil and that the only zone valve is the one for the rads, normally the cylinder coil would have its own zone valve wired in series with a cylinder thermostat that would normally be set at 60C.

    You just may have a system like this (which I have never seen) https://www.plumberparts.co.uk/advice/heating-systems/y-plan-heating-system


  • #8
    MiketheMechanic
    Registered Users, Registered Users 2 Posts: 903 ✭✭✭MiketheMechanic


    agusta wrote: »
    you could test the hot water zone in its own and see what you get.things can change since the summer.is it a pressurized system or do you have a small tank in the attic


    There's a small tank in the attic for the system.


  • #9
    agusta
    Closed Accounts Posts: 1,590 ✭✭✭agusta


    Did you check to see how much water is in the small tank in the attic and that the float valve is working freely.if the copper cylinder is upstairs and higher than the rads ,its the first affected if water content is slightly low


  • #10
    MiketheMechanic
    Registered Users, Registered Users 2 Posts: 903 ✭✭✭MiketheMechanic


    agusta wrote: »
    Did you check to see how much water is in the small tank in the attic and that the float valve is working freely.if the copper cylinder is upstairs and higher than the rads ,its the first affected if water content is slightly low


    Just checked the small tank there now - water seems to be at normal level and float valve operates when I push float down.


  • #11
    agusta
    Closed Accounts Posts: 1,590 ✭✭✭agusta


    As john was saying,can you run the hot water separate from the rads and see how it works then


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  • #12
    John.G
    Registered Users, Registered Users 2 Posts: 3,561 ✭✭✭John.G


    agusta wrote: »
    As john was saying,can you run the hot water separate from the rads and see how it works then

    Not clear to me at least the system configuration but a few things to check:

    IF the hot water has its own zone valve then check that this is opening/opening fully. Some zoned systems (see link above) may be "Y" plan, very unlikely but easy to check out. Some zoned systems have a separate pump for each zone (no motorized valve) IF so check that the associated pump is running. All systems above should be wired in series with a cylinder thermostat, IF so check thermostat setpoint (60C). Also just feel the copper flow and return pipe close to the cylinder, the flow pipe should be almost as hot as the boiler flow, the cylinder return should be cooler, if very cold it might suggest a circulation problem, if very hot it might suggest that the coil has limescale, unlikely as this would happen gradually and this problem seems to have been recent/sudden?
    One other thing maybe worth re checking is the cylinder return balancing valve which is probably a gate valve, IF it is fully open as stated then shut it, it should take 4 to 5 full turns (clockwise) to do this, then re open it, again 4 to 5 turns (anticlockwise) to achieve this.
    Can't offer any other obvious things to check at the moment.


  • #13
    John.G
    Registered Users, Registered Users 2 Posts: 3,561 ✭✭✭John.G


    Hi Mike,
    Any update/fix for your problem?.


  • #14
    MiketheMechanic
    Registered Users, Registered Users 2 Posts: 903 ✭✭✭MiketheMechanic


    Hi folks, sorry for the delay.
    I think it is better. I opened and closed the motorised valve next to the boiler a few times by cycling the power while the heating system was running - in case it was stuck partially open/closed. This one controls the flow to the rads in my system.
    In the hotpress, I also closed the return balancing valve fully, then opened it 2 or 3 turns.
    I bled one rad in the attic that had a very tiny cold spot along the top.
    I'll keep an eye on it - cold weather coming :-)


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