Combi or System Boiler

Discussion in 'Plumbers' Talk' started by Muzib, Jul 30, 2014.

  1. Muzib

    Muzib New Member

    A 4 bedroom house with 2 bathroom (1 on suit shower only, other with both bath and shower) and an additional toilet. I am planning to replace old regular boiler. Current mains water flow rate 20L/Min and pressure 3 Bar. After discussing with couple of engineers, some suggested system boiler with unvented cylinder, some suggested Worchester high flow CDI 550 combi boiler. Combi boiler will save space but will the water flow/pressure be ok if both bathroom are in use? Also, if possible I want to move boiler/cylinder to loft space. Could any expert help me with this?
     
  2. CraigMcK

    CraigMcK Screwfix Select

    I've no knowledge of how good the 550 is, but I moved house from a 250L unvented to a large'ish combi with water store and I would go back to the unvented anyday. I understand the cost implications of heating a large amount of water that may not be used, but the time to fill a bath from combi cannot be underestimated.

    I doubt you could run a bath & shower at the same time on any combi if that is also a possibility for you.
     
  3. Muzib

    Muzib New Member

    Thanks a lot for sharing your experience. I'll possibly stick with the system boiler. For 2 bathroom, would 180 L unvented cylinder do the job? Or, do I need a bigger one? Any suggestion?
     
  4. tom.plum

    tom.plum Screwfix Select

    there's no denying that you'll always get better pressure for an unvented, the size of the cylinder is the amount of hot water you have in storage so the bigger the cylinder the more hot water you have, here's a little off beat home spun explaination video that explains why,

     
    kiaora likes this.
  5. plumberboy

    plumberboy Well-Known Member

    I would go with system boiler and unvented cylinder without a doubt.
     
  6. plumberboy

    plumberboy Well-Known Member

    Any up and coming video updates from the greenhouse Mr plum.
     

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