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HW not heating up enough

  • 24-02-2019 10:28AM
    #1
    danoriordan1402
    Registered Users, Registered Users 2 Posts: 702 ✭✭✭


    Noticed this in the last week or so, running out of HW in the showers quick enough - usually a couple of hours in the morning and evening gave us plenty. Gas Central heating, timer controlled. When the timer kicks on I can hear/feel the circulation pump running and feel the flow into the cylinder so that side seems to be working fine.

    The stat however seems to struggle to get over 40 degrees and the top of the boiler feels a lot hotter, even on the outside, through the insulation. Bottom feels cold. Its a dual coil, 500l cyclinder, the solar has been off for a few months.

    Any ideas would be appreciated before I call the plumber


Comments

  • #2
    John.G
    Registered Users, Registered Users 2 Posts: 3,916 ✭✭✭John.G


    danoriordan1402 wrote: »
    Noticed this in the last week or so, running out of HW in the showers quick enough - usually a couple of hours in the morning and evening gave us plenty. Gas Central heating, timer controlled. When the timer kicks on I can hear/feel the circulation pump running and feel the flow into the cylinder so that side seems to be working fine.

    The stat however seems to struggle to get over 40 degrees and the top of the boiler feels a lot hotter, even on the outside, through the insulation. Bottom feels cold. Its a dual coil, 500l cyclinder, the solar has been off for a few months.

    Any ideas would be appreciated before I call the plumber

    Bottom would/should normally be cold as the solar coil is the on the lower end and the boiler heating coil is further up heating maybe the upper 250 litres.

    Is there a (gate) balancing valve on the outlet from that upper coil, if so, open it fully (~ 5 turns) then fully close it and reopen it to between 1 to 1 and a half turns.

    Check the boiler stat setting, should be = or > 65C

    Check that the cylinder stat is set to 60C.

    Check that motorized valve is opening fully.


  • #3
    danoriordan1402
    Registered Users, Registered Users 2 Posts: 702 ✭✭✭danoriordan1402


    John.G wrote: »
    Bottom would/should normally be cold as the solar coil is the on the lower end and the boiler heating coil is further up heating maybe the upper 250 litres.

    Is there a (gate) balancing valve on the outlet from that upper coil, if so, open it fully (~ 5 turns) then fully close it and reopen it to between 1 to 1 and a half turns.

    Check the boiler stat setting, should be = or > 65C

    Check that the cylinder stat is set to 60C.

    Check that motorized valve is opening fully.

    boiler set to 70
    stat at 60
    no balancing valve that I can see
    Not sure if I have motorized valves, there is an inline pump for hw thats separated from the 2 x underfloor inline pumps. It goes into some kinda mixing box..


  • #4
    John.G
    Registered Users, Registered Users 2 Posts: 3,916 ✭✭✭John.G


    danoriordan1402 wrote: »
    boiler set to 70
    stat at 60
    no balancing valve that I can see
    Not sure if I have motorized valves, there is an inline pump for hw thats separated from the 2 x underfloor inline pumps. It goes into some kinda mixing box..

    Check that the pump is actually running, what make/model is it?, there is usually a NR valve immediately after the pump as well, this may be stuck/sticking but would need a system drain down to check/renew it.

    Feel the coil flow (top) pipe about 4/6 ins from the cylinder, it should be red hot (70C) the coil return should be warm/fairly hot depending on the cylinder hot water temperature.
    Is the boiler cycling on/off a lot on HW duty only, a oil boiler will still cycle a fair bit as it is always at full firing but a gas fired boiler due to modulation should rarely cycle on HW duty only.

    You said in first post that the pump is running so NR valve could be the culprit but carry out other tests as well.


  • #5
    danoriordan1402
    Registered Users, Registered Users 2 Posts: 702 ✭✭✭danoriordan1402


    John.G wrote: »
    Check that the pump is actually running, what make/model is it?, there is usually a NR valve immediately after the pump as well, this may be stuck/sticking but would need a system drain down to check/renew it.

    Feel the coil flow (top) pipe about 4/6 ins from the cylinder, it should be red hot (70C) the coil return should be warm/fairly hot depending on the cylinder hot water temperature.
    Is the boiler cycling on/off a lot on HW duty only, a oil boiler will still cycle a fair bit as it is always at full firing but a gas fired boiler due to modulation should rarely cycle on HW duty only.

    You said in first post that the pump is running so NR valve could be the culprit but carry out other tests as well.

    thanks - will check these out


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