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Worcester Bosch R29 Boiler / CH Balancing Q's

Discussion in 'Plumbing and Central Heating' started by RidwarePhil, 2 Oct 2008.

  1. RidwarePhil

    RidwarePhil

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    I am trying to get our central heating system and have a few questions about my boiler.

    It is supplying 7 rads with TRV upstairs and 7 rads + underfloor heating in 1 room downstairs.

    Pump is currently running on speed 3 - what will happen if I slow this down?

    What temp should I be running the centra heating at - its currently at 65C

    What temp difference should there be between the boiler flow and return?

    Is it normal that my underfloor heating has a seperate pump installed? The underfloor heating doesn't seem to have a thermostat. Is this normal?
    Do they normally have the equivalent of a lockshield valve?


    Thanks in advance
     
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  3. D_Hailsham

    D_Hailsham

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    What boiler do you have? (Make and exact model)

    1. Temp Difference depends on boiler and system design

    2. Run the boiler at max temperature and let the controls control it.

    3. If you slow the pump down, you may overheat the boiler, but it all depends on the boiler and the system.

    Need more info to give a more helpful answer ;)
     
  4. Agile

    Agile

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    The underfloor is a seperate loop and is circulated by its own pump.

    They usually have a thermostatic blending valve which keeps the UFH at about 50°C flow and about 40°C return. They usually have an adjusting valve to set the flow rate and hence the temperature differential.

    In your case you can probably set the flow rate to give just 5° differential if you need more heat output. However, the exact operating parameters yet again depend on the boiler and its most efficient operating conditions.

    Tony
     
  5. RidwarePhil

    RidwarePhil

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    Thanks guys

    The Boiler is a Worcester Condensing Boiler Model- ZB 7-28 R28 HE
    Recently serviced
    Boiler is set to 67C and increaseing the temp by 5C really made a huge difference

    I dont have thermocouples yet so cant measure the temp difference between flow and return but it feels very similar.

    If I slow the pump down from 3 to 2 then the rads start to go cold again.

    Boiler will go to 75C (will this improve the efficiency or just waste gas?)


    Underfloor heating plumbing looks complex.

    Two horizontal pipes - bottom one flow (54C) and top one return (52C)
    Grundfos alpha 25-60 pump fitted between flow and return
    To the left hand side of the pump there appears to be a direct connection between flow and return with the return temp gauge on and a black knob at the top with +/-

    Any ideas what this is? flow rate?
    I tried turning this but it seems to be locked.

    Any further advice will be appreciated.

    Thanks Phil
     
  6. D_Hailsham

    D_Hailsham

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    You have proved to yourself the difference 5C makes; another 8C will have even more effect. It will not waste any gas as the boiler is turned on and off by the room thermostat. (You do have a room stat, don't you?) The higher temperature will make the radiators heat up more, so the house will heat up faster, so you can turn the heating on later. In any case the boiler automatically adjusts the flow temperature to suit the requirements.

    Wow , that's very technical and scientific! An infrared thermometer (about £20 from Maplin on-line) would do the trick.

    Your boiler is designed to work with a 20C temperature difference. I only hope the designers of your system took this into account when sizing the radiators! (Radiator outputs are quoted for a temperature diff of 11C. The output is reduced by about 15% when the differential is 20C. This is compensated for by over-sizing the radiator about 20%)

    Then you need to keep the pump on 3



    ;)
     
  7. RidwarePhil

    RidwarePhil

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    Thanks

    The thermostat is upstairs on the landing

    Any further comments on the Under floor heating?
     
  8. DIYnot Local

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