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New Gas Boiler Advice - Combi or something else?

Discussion in 'Plumbing and Central Heating' started by Betty B, 13 Jan 2021.

  1. Betty B

    Betty B

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    Hi guys, I'm hoping to stock up a bit of knowledge before getting some quotes for a new boiler as I don't want to look like a dumb blonde and pay for unnecessary work.

    I have a Baxi Solo 50/4RS in the kitchen which I'm told is over 25 years old and inefficient. It's a bit noisy but heats the house and water well enough. There are 8 radiators, all under 5 years old fitted with TRVs and gravity fed from a plastic tank in the loft. The Water tank in the loft is a sealed type with an expansion tank providing HW at mains pressure, which is nice, to 1 bath and 1 shower room both with basins. The controller is Hive. My only gripe is that it takes an age for HW to reach the kitchen but perhaps the Baxi needs to be retired before it croaks.

    Rather than have someone run new pipes up into the ceiling and under the bathroom, landing and bedroom (this would be a major pain and cost as the upstairs floor has just been done in Oak) Would it be possible for them to fit a Combi Boiler with the Hot Water outlet just feeding the Kitchen tap and leave the existing tank/radiator arrangement fed by the Heat outlet, just like the Baxi? I'm thinking the boiler is pushing feed water around in a loop so the tank just looks like another radiator when the controller opens the valve.

    Thoughts and advice muchly appreciated.
    BB
     
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  3. muggles

    muggles

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  4. Betty B

    Betty B

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    Thanks Muggles, that's good to know. Reading boiler descriptions on the screwfix site and other advice I wasn't sure if it was something prohibited by regulations.

    The Baxi is 14Kw so a 24Kw Combi should be good enough for heating. I guess the Hot Water pressure might not be so good but that's why I wanted to keep the Unvented tank.
     
  5. muggles

    muggles

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    No, it's absolutely fine. The Xclusive 24 is actually maximum 18kW to heating. Yes you're right that it wouldn't produce a fantastic flow rate for the whole house but it'll be just fine for a single kitchen tap, with the rest off the existing cylinder
     
  6. vulcancontinental

    vulcancontinental

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    Look for the modulation range of the boiler, anything from 1:7 up will be fine and also chose one that can be range rated as a, for example, 35kW combi with a good flow rate could have out of the box a heating output of 30 kW, far too much for your house. By range rating it the heating output can be limited to the property requirements and the domestic hot water would remain unaltered. note: 35 kW is not really necessary for sink tap but I used it as an example.

    If possible operate the heating stored water system with priority hot water reheat using for example OpenTherm controls which will optimize efficiency.
     
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  7. Betty B

    Betty B

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    Thanks Vulcan, that's a good point to ask the gas guy to make me sound as if I know what I'm talking about.
     
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