Worcster Si or CDi, that is the question

Discussion in 'Plumbing and Central Heating' started by pg325, 13 Aug 2011.

  1. pg325

    pg325

    Joined:
    13 Feb 2005
    Messages:
    42
    Thanks Received:
    0
    Country:
    United Kingdom
    I'm going to replace my current WB 240 and have been recommended the Greenstar Si or Greenstar CDi.

    My choice of either 25/30 Si or 27/30 CDi, what I want to know (apart from the obvious DHW and BTU) is what is the main difference with these boilers.

    Both seem to offer independent DHW temp, DHW flow is the same (ish), any ideas.
     
  2. Sponsored Links
  3. bengasman

    bengasman

    Joined:
    28 Jan 2005
    Messages:
    34,181
    Thanks Received:
    3,124
    Location:
    London
    Country:
    United Kingdom
    CDI is better build quality. SI is a tarted up version of the budget boiler i-model.
     
  4. ServiceNumpty

    ServiceNumpty

    Joined:
    9 Sep 2007
    Messages:
    6,962
    Thanks Received:
    1,697
    Location:
    Nottinghamshire
    Country:
    United Kingdom
    The cdi is manf in Germany, different pump, heat exchanger, diagnostics, sturdier, generic hydroblock as the si/i series. Easier to service than the si/i series, both will be a pain in ass to repair though.
     
  5. boilerdoktor

    boilerdoktor

    Joined:
    14 May 2009
    Messages:
    2,882
    Thanks Received:
    1,247
    Location:
    Tintagel cornwall
    Country:
    United Kingdom
    the cdi is more efficient!..both easy to work on should you need to( you probably wont)
     
  6. andycox

    andycox

    Joined:
    10 Jun 2011
    Messages:
    4
    Thanks Received:
    0
    Country:
    United Kingdom
    :eek:
    As my learned friend said CDi is better and cheaper to run, last longer
    GET ONE!

    3+ people or 3 beds = 30Kw
    small place fit 24 is not worth buying CDi go Si cheaper
     
  7. ianniann

    ianniann

    Joined:
    22 Mar 2009
    Messages:
    678
    Thanks Received:
    91
    Location:
    Manchester
    Country:
    United Kingdom
    Fancier modulating pump. The major marketing points they use to distinguish the two ranges are that the CDi has a "modulating pump" and is "fulliy condensing in hot water mode".

    The modulating pump is true and certainly uses less electricity than the non-modulating pump but it is still a pretty hungry pump. Better to have it than not though. You may also notice higher noise from the Si pump, especially when TRVs are shutting down.

    The thing about condensing in hot water mode is mostly a steaming bag of marketing ... errr ... stuff. Both boilers condense, not fully not not zero, in both heating and hot water modes. Details depend on the settings and operating conditions. The CDi has a larger heat exchanger which helps to extract condensing energy even when the output temperature is above the dewpoint. The difference isn't huge (1%-2% overall?), but again it is better to have it than not.

    The CDi can also be fitted with a wider range of controls, including more sophisticated modulating controls and weather compensation. This really should be the biggest selling point in terms of features, although the CDi is generally more robust (and a lot heavier!).
     
  8. 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

     
  9. Sponsored Links
Loading...

Share This Page