Sizing rad's with boiler upgrade in mind - delta_T50/_T60 ??

Discussion in 'Plumbing and Central Heating' started by Antony2008, 14 Apr 2008.

  1. Antony2008

    Antony2008

    Joined:
    6 Apr 2008
    Messages:
    39
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    I’m currently sizing some additional radiators for an existing central heating system (all rad’s have TRV’s) that has a non condensing combi boiler that’s around 8 years old. The new radiators will be fitted in the next few weeks but I’m planning on changing my boiler in a year or so.

    Am I correct in assuming that radiators that are served by new condensing boilers should be calculated using delta_ T50, and delta_T60 should be used for non condensing boiler systems? If so then I believe I have to buy radiators that have too large a capacity for my current boiler in anticipation of fitting a condensing boiler that runs at a lower output temperature.
    For example - for a calculated room requirement of 4110 Btu, a radiator of Btu/h 4587 at delta_T60 should suffice for my current boiler. When I then change to a condensing boiler, I believe that this radiators capacity reduces to an output of Btu/h 3620, thereby not providing sufficient heat for the room.

    I’d appreciate if someone could confirm (or otherwise) the above assumptions before I buy inappropriate radiators.

    Thanks in advance.
    Antony
     
  2. Sponsored Links
  3. Agile

    Agile

    Joined:
    26 Jun 2004
    Messages:
    64,039
    Thanks Received:
    4,595
    Location:
    London
    Country:
    United Kingdom
    Most rad makers data now is stated at T50 and thats what you should use.

    Older rads were sized by the installer for T60 but since then the insulation has usually been improved. Also most heat loss programs used to oversize the rads anyway.

    Many people are still using heat loss programs based on T60 and thats where many people can get into difficulties.

    Its all very hit and miss anyway!

    You only need the full output when the temperature is at - 1 ° C anyway. Thats hardly a couple of days a year in low lying southern areas.

    Tony
     
  4. ChrisR

    ChrisR

    Joined:
    24 Jul 2003
    Messages:
    24,299
    Thanks Received:
    1,407
    Location:
    London
    Country:
    United Kingdom
    Places like Yorkshire don't matter to Tony :D :LOL: :eek: :p :cry:

    And the standard is now -2ºC
     
  5. D_Hailsham

    D_Hailsham

    Joined:
    18 Oct 2007
    Messages:
    10,587
    Thanks Received:
    1,344
    Location:
    Kent
    Country:
    United Kingdom
    deltaT is the difference between the mean radiator temperature and the design room temperature. The reason for adopting a deltaT of 50°C instead of 60°C was to bring England into line with the rest of Europe. It also saves energy as you only need to raise the water temperature to 75°C instead of 85°C. The conversion factor given in radiator calculators for different deltaT assume that the flow temperature is 75°C and the return is 65°C. The change in deltaT is due to a higher/lower room temperature.

    Some "experts" suggest that, for maximum efficiency, the boiler should always working in condensing mode. To achieve this, the return temperature has to be below 60°C. The flow temperature required to provide this return temperature will depend on the boiler. Unfortunately the flow and return temperatures will not be as assumed in the rad literature, so the conversion factors will be different as well.
     
  6. gas4you

    gas4you

    Joined:
    23 Feb 2007
    Messages:
    21,178
    Thanks Received:
    1,912
    Location:
    Norfolk
    Country:
    United Kingdom
    I always use deltaT50 and run the boiler at 60C (combi) 65C conventional boiler.

    Never had any probs reported back to me yet ;)
     
  7. Antony2008

    Antony2008

    Joined:
    6 Apr 2008
    Messages:
    39
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    Thanks for your replies & comments everyone.

    I reckon common sense suggests using deltaT50, ensuring that I'm 'future proofed' when I eventually go for the condensing boiler.

    Cheers
    Antony
     
  8. Agile

    Agile

    Joined:
    26 Jun 2004
    Messages:
    64,039
    Thanks Received:
    4,595
    Location:
    London
    Country:
    United Kingdom
    """The British standard BS 5449 states that the external design temperature should allow for all but the most extreme conditions and a figure of -1 degrees C is usually chosen. Many developers still rely on this minimum BS Standard of -1 degrees C irrespective of the anticipated external temperature extremes."""

    Has BS 5449 been revised then?

    Tony
     
  9. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
  10. Sponsored Links
Loading...

Share This Page