Which boiler

My boiler is now 20 years old and am probably looking to replace.
I am sure I want worcester bosch but not sure which model or size.

I have it down to Greenstar 4000  25/30w and 28cdi/32 cdi compact.

Probably going with Boxt. 3 bed house, one bathroom.

Any advice??

Comments

  • Ganga
    Ganga Posts: 4,034
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    What type/model is your currant boiler? ,how many radiators ,showers ,baths etc.
    ITS NOT EASY TO GET EVERYTHING WRONG ,I HAVE TO WORK HARD TO DO IT!
  • mexican_dave
    mexican_dave Posts: 247
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    To directly answer the question of size - read the Output of your boiler expressed in kW, on a plate or label on the boiler case. That's the Output someone once decided your house needed. As it's 20 years old your house has likely had energy saving improvements, so it might useful to have some kind of energy assessment. Do you have a fairly recent EPC which tells you your Space Heating & Water Heating requirements, will need to do some maths to bring to an Output requirement? Or just show it your boiler engineer!
    I doubt you are going to fit this boiler yourself, so get a boiler engineer to suggest the replacement.
    Caution, if you go to the trouble of selecting the model/brand of your boiler, you boiler engineer might want to fit a different model/brand, one he is more familiar with and gets a discount on from his supplier. I am not saying he will give you his discount, but it will have a bearing on his quote to you.
    Not familiar with the boilers you are looking at but personally I don't like Combi boilers, I like CH and a factory-insulated indirect HW Cylinder. So my new boiler is a "system boiler" it heats a circuit of pumped water and a separate motorized valve, sends the water to the cylinder or to the radiators as required. I find it energy efficient with room stat and cylinder stat, and can always fill a bath, not something a Combi can be relied to do! Ask your boiler engineer especially if you have a cylinder cupboard!
  • Lorian
    Lorian Posts: 5,674
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    The 4000 is one of their newer models.

    Check the flow rate of your cold water.

    How many showers are fed off the boiler hot water?

    What controls are being offered?
  • FreeBear
    FreeBear Posts: 14,248
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    Greenstar 4000 will heat 11l/min by 40°C, and 12.3l/min by 35°C - Assume an inlet temperature of 10°C in the winter, and that should cope with filling a bath quite nicely (depending on your actual cold water flow rate).
    A modulation range of 3.2KW to 30.6KW is pretty good, and if you can run it at the lower end, you should get excellent efficiency.
    The 28CDi will only modulate down to ~7.15KW - Poor in comparison to the Greenstar and Viessmann boilers. If you go with the 28CDi, you'll probably find it short cycling which is bad for efficiency.

    When you get a new boiler, give some thought to fitting larger radiators all round (with TRVs) - This will enable you to run at a lower flow temperature and hit peak efficiency. I recently fitted a new boiler and went 30-50% larger on the radiators all round. Max flow temperature is set for 50°C, but much of the time it is running at 40-45°C. Looking at the data collected from the boiler, it spends most of it's time modulated down to 3-4KW output. Combined with the low flow temperatures efficiency should be pushing 98% (I need to instrument gas flow & heat output).
    Her courage will change the world.

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  • Soconfused14
    Soconfused14 Posts: 73
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    @ lorian only one bathroom with shower over bath. 
    @mexican_dave I had the last boiler put in and it was a greenstar junior 28i. Im not really interested in a system boiler. And no EPC as wasnt a thing when I bought the house 20 years ago.
  • ThisIsWeird
    ThisIsWeird Posts: 4,458
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    edited 2 February at 7:33AM
    @ lorian only one bathroom with shower over bath. 
    @mexican_dave I had the last boiler put in and it was a greenstar junior 28i. Im not really interested in a system boiler. And no EPC as wasnt a thing when I bought the house 20 years ago.
    Are you happy with your current boiler's performance? Giving a good shower? 
    Or would like like a little more?
    If 'happy', then there's no obvious reason I can think of to look any further than your own fav, the Greenstar 4000 30kW. Don't go smaller.
  • Soconfused14
    Soconfused14 Posts: 73
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    @ThisIsWeird The shower is good, but I have a limiter on the shower so uses less water anyway. 
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