Best Combi, gas, Vaillant EcoTec?

Discussion in 'Plumbers' Talk' started by BMC2000, Sep 11, 2019.

  1. BMC2000

    BMC2000 Active Member

    Hi, 3 story semi. Ensuite with shower in loft, main bathroom on 1st and toilet and kitchen on ground. 4 bedrooms. Double panel Myson rads and Thermostatic valves to most rooms. New extension planned and converting from oil to gas and was thinking of the above. Will re pipe the ground and 1st (2nd done 2 years ago).

    Any advice on best suited boiler in terms of performance, economy and dependability?
  2. KIAB

    KIAB Super Member

    Never had a Vaillant break down in nearly 25 years of use,been through the various models, presently got a 824 here,10-11 years old, only new part fitted,has been a new heat exhanger end of 2017.
    Been thinking about replacing it with a new Vaillant Green iQ Ecotec 835 next year,but there nothing wrong with my 824,could go on for years.
    Last edited: Sep 11, 2019
    BMC2000 likes this.
  3. PawelM

    PawelM New Member

    I have ecotec plus 825, plenty of power and no issues so far
  4. Hfs

    Hfs Active Member

    I would go for an inter gas combi boiler....Only four moving parts.
  5. kiaora

    kiaora Screwfix Select

    If your budget allows, an unvented cylinder and vailliant combi, with heating and hot water zones,
    Will give good performance, as long as incoming water main has good flow rate.

    The cylinder can feed the bathroom and combi hot water,

    Will need to consider the position of the boiler and cylinder, to keep the hot water draw off short,

    If combi in on top floor , make that feed shower in loft.
    And cylinder on middle or ground floor ?

    A combi will only deliver a flow rate say 30 Kw @ 12 lpm.

    It could cost less to have electric shower in loft ?

    Good luck
  6. ajohn

    ajohn Screwfix Select

    :) All of the modern electronic checks haven't got to you yet - next year if you change it might eventually.

    Many "heating engineers" say combi combi combi but really they should look what is in the house. Lots of taps, extra bathrooms and showers aren't so simple if several used at the same time. Water flow rate into the property can be a problem as well. Not easy to measure as many modern taps have restricters in them. Some bath taps may not have. Just needs a measuring jug and a watch. The boiler water heating spec's need looking at as well. 40C hot water is decent for most uses providing it doesn't drop off and the flow rate is high enough.

    Combi - flow rate into the house is the limit and it's capacity for heating water. Open 2 say taps and the flow rate may not split evenly.

    Pressurised hot water tank has the same flow rate limit as a combi. Water going out has to be replaced by water going in but the water in the tank will be at a set temperature what ever the flow rate is. Currently via a different type of system ours is at 80C so a pressure regulator on cold to taps etc and not to the water heating and a TMV helps a lot but it's still not perfect.

    Vented hot water tank and header tank. If the pipe work is well designed fine but it wont be so multiple taps etc opening are likely to interfere with each other. However where I have experienced this type of system it's better than the others.

    When we moved in here heating was via economy 7. Bathroom on ground floor and 1st floor and just taps on the 2nd floor. Ground and 1st floor both had gas under sink style water heaters. That worked fairly well but flow to baths did mess up flow to bedroom sinks on the same floor somewhat.

    :) Like Peter said - good luck. We are still using an old gas Worcester Heatslave. It uses a heat store. Basic idea is that this has enough capacity to fill a bath but water will cool significantly. 3min after the bath has been run it will be back up to full temperature. No one makes a system like that any more. Heatstores for multiple baths are now massive and take a long time to heat up. In some ways I wish we had bought the higher power one but it was over the top for heating. They were popular in pubs, clubs and various businesses that wanted lots of limited quantities of hot water but also worked rather well in a home.

  7. The Teach

    The Teach Screwfix Select

    Finding out the customers hot water demands and then installing a system to suit the customers demands is important.

    Some customers want several super high pressure showers to be used simultaneously,some just a single sensible shower arrangement.

    often a gas combination boiler is the wrong choice,often a gas combination boiler is the best choice. Only a survey and a needs & demands chat will sort out the best boiler :)
  8. ajohn

    ajohn Screwfix Select

    Didn't mention the advantage a heat store has over a pressurised hot water tank. They take full mains pressure. What the makers do now though is limit the max kw input according to size so the heat up times are much longer that Worcester's which was also incredibly simple.

  9. ajohn

    ajohn Screwfix Select

    :) Whops - I suspect Heatslave should have been HiFlow. Not sure.

  10. KIAB

    KIAB Super Member


    Confusing combi with system boiler:confused:
  11. ajohn

    ajohn Screwfix Select

    I have a feeling we will finish up heat only plus a heat store plus a phone call asking why I can't stuff modulated 30kw through a smaller one than they would say for 2 baths / n bedrooms.

    Why - mains pressure less a bit for losses hot water.

  12. ajohn

    ajohn Screwfix Select

    This is one of them. There are several about but doubt if I will add solar.

  13. ajohn

    ajohn Screwfix Select

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