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Temp of return pipe on unica sensor boilers

  • 06-01-2014 7:51pm
    #1
    Marycelineok
    Registered Users Posts: 11 ✭


    What is the reason for a thermostat on the return pipe in a Moderator Unica Sensor boiler? Will it matter if it is reduced from the recommended 55c to 40c as long as the central heating temp is no more than 10c higher?

    Marycelineok


Comments

  • #2
    Dtp1979
    Registered Users, Registered Users 2 Posts: 12,839 ✭✭✭✭Dtp1979


    Marycelineok wrote: »
    What is the reason for a thermostat on the return pipe in a Moderator Unica Sensor boiler? Will it matter if it is reduced from the recommended 55c to 40c as long as the central heating temp is no more than 10c higher?

    Marycelineok
    I think the stat is set to control a mixing valve that won't let water to the house until the return is 55 to the boiler. It prevents condensation inside the boiler


  • #3
    Marycelineok
    Registered Users Posts: 11 ✭Marycelineok


    Thanks for that. House is warmer at lower temp because of constant heat. How will I know if there is condensation within boiler and what problems will it cause?

    Would running it at a lower temp for say 5 days and then at higher temp over weekend stop condensation?


  • #4
    Dtp1979
    Registered Users, Registered Users 2 Posts: 12,839 ✭✭✭✭Dtp1979


    Marycelineok wrote: »
    Thanks for that. House is warmer at lower temp because of constant heat. How will I know if there is condensation within boiler and what problems will it cause?

    Would running it at a lower temp for say 5 days and then at higher temp over weekend stop condensation?

    I doubt it to be honest. Condensation will rot your boiler. It is possible your pipe stat isn't accurate. Perhaps change it for a new one just to be sure first. Only around a tenner


  • #5
    esox28
    Registered Users, Registered Users 2 Posts: 800 ✭✭✭esox28


    As dtp rightly pointed out the return senson is controlling a balanced return mixing valve, which works to maintain the boilers cast iron heat exchanger at a set temp in order to minimize boiler condensation and thermal shock.

    Imo the return set temp should only be adjusted by a qualified install or service eng.

    Have you tried adjusting the boilers main thermostatic controls to adjust the level of heat generated or are you just connected to a buffer storage?


  • #6
    Marycelineok
    Registered Users Posts: 11 ✭Marycelineok


    There is a computerised control on top of boiler which allows us to set the ch temp. We were advised that the return pipe should be set 10c below ch temp.
    Operating instruction manual state the minimum return temp should be 55c which means ch minimum is 65c. However this is very difficult to maintain. Once temp falls below about 67c the flow to house is reduced and stops at 60c. This means we have to feed boiler every 2 to 3 hours and is very costly. With temp set at 50 and 40 resp we have constant heat to house rather than intermittent. This is more comfortable and the boiler only needs feeding every 8 to 10 hours and cost considerable less to run. However I do not wish to damage the boiler and would welcome any suggestions.

    We do not have buffer storage


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  • #7
    esox28
    Registered Users, Registered Users 2 Posts: 800 ✭✭✭esox28


    Maybe its a buffer you need to control the flow temp to the house, if the boilers mi states min return temp 55*c as we discribed for condensation and thermal shock I don't see any alternative to the stated min return temp.


  • #8
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    A lot cheaper & easier to install but with similar results would be a low loss header, which in affect is a mini-buffer tank.
    I installed one in my own house to ensure I keep the boiler in condensing mode for as long as possible & reduce boiler short cycling as I have UFH with an oil boiler.

    Works a treat & very little space required.


  • #9
    Dtp1979
    Registered Users, Registered Users 2 Posts: 12,839 ✭✭✭✭Dtp1979


    shane0007 wrote: »
    A lot cheaper & easier to install but with similar results would be a low loss header, which in affect is a mini-buffer tank.
    I installed one in my own house to ensure I keep the boiler in condensing mode for as long as possible & reduce boiler short cycling as I have UFH with an oil boiler.

    Works a treat & very little space required.

    Do they work with solid fuel Shane?


  • #10
    esox28
    Registered Users, Registered Users 2 Posts: 800 ✭✭✭esox28


    The boiler in question would have a 110ltr boiler content llh wouldn't do much min of 800ltr buffer needed.


  • #11
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Dtp1979 wrote: »
    Do they work with solid fuel Shane?

    Sorry, dismiss what I posted. Wasn't thinking.


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