Boiler and cylinder for new system

Discussion in 'Plumbers' Talk' started by baracus, Jun 18, 2018.

  1. baracus

    baracus Member


    As part of a my extension works we have underfloor heating to the ground floor and radiators on middle and loft floors. We have 4 bathrooms but there are only 3 of us in the house. The builder is recommending a telford sleeper tank (250l) and a vaillant 430 boiler, he says Telford offers good value for money compared to the Heatre Sadia equivalent and that the 30kw boiler is adequate for our use. The sleeper has been suggested beacuse there is a large void under the stairs that would take the tank nicely and use an otherwise dead space.

    Id be happy to hear views on Telford cylinders and the 430 boiler.

    Many thanks in advance.
  2. Heat

    Heat Screwfix Select

    Telford unvented cylinders are good and reasonably priced.
    You are better with a heating engineer giving you advice, rather than a builder.
    However, his advice was probably to avoid the over expensive Megaflo (Heatre Sadia), which many would agree with.
    Note that Heatre Sadia also make Center Brand cylinders and are a lot cheaper. Most unvented units have similar parts/controls and 25 year warranty.
    Your boiler should be sized for the heat loss calculation of your house, including the hot water.
  3. rogerk101

    rogerk101 Screwfix Select

    If you're starting from scratch, you really should speak with a heating engineer. If he/she doesn't recommend a condensing combination boiler as the first option, then look for another engineer.
    I had a new system installed in a house several years ago and I went for something like what you described above. It was all very well when we had a busy household with a family of 4. However, when the kids left home and either I or my wife was away on business, it was extremely wasteful to keep a full 250 litre tank of hot water for one person. It's even wasteful for 2 people, ans neither my wife nor I take hour-long showers. The beauty of a combi boiler is you only heat the water when you need it, you only heat as much as you need, and you never run out if you have a sudden wave of people coming home from a muddy adventure.
    Just because you have space for a big tank under your stairs shouldn't mean that you need to fill it up with something that stopped being useful at least 20 years ago when combi boiler became the norm.
    KIAB likes this.
  4. KIAB

    KIAB Super Member

    And fitting a large combi with a high flow rate (mains dependent),the combi can be modulate down Valliant 843 (wide modulation range of up to 1:10, so 4.3Kw - 33.4Kw heating) to match system,so more efficent to run.

    As an example the Vaillant ecoTEC Exclusive Green iQ 843 has a flow rate of 17.8ltrs, plus it can use Vaillant V Smart to control your heating with your phone.

    And it has 7 year warranty when registered by an Advance installer,which can be extended to 10 years, again when registered by an Advance installer..
    Last edited: Jun 19, 2018
  5. Heat

    Heat Screwfix Select

    Combi boilers can’t cope with large hot water demand, like several bathrooms in use, so be aware of their limitations.
    You could have a combi boiler, but also a hot water cylinder if you wished, therefore with hot supplies coming from different source.
  6. kiaora

    kiaora Guest

    I installed a bespoke system for a large house with fluctuations in hot water demands,

    Answer, combi with 3 zone valves, combi feeds kitchen and en suite shower,
    1 zone unvented hot water for house,
    1 zone heat upstairs
    1 zone heat downstairs

    35 Kw vailliant combi, with filter and bypass, job sorted !

    Add more zones to requirements of building, simples


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