In the next few months I will need to change my boiler I currently have a valiant but unsure what today best boiler is in reliability, economical
Any sujestions ?
Any sujestions ?
New Combi boiler for a 3 bed semi choice
- Thread starter markymark2406
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This question has been asked here many times.
You will learn that people have differing and often strongly-held views!
I suggest typing "which combi boiler" or "which boiler" into the search box and settling down for a long, long read.
You will learn that people have differing and often strongly-held views!
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From what I am told, for a boiler to run efficient the return water needs to be cool, and to be able to turn off or down when rooms not occupied it needs a fast recovery time, this means it is all down to the size of radiators.
So I will give an example, out all day, no fixed time for return, and the geofencing thermostat picks up you are returning one hour before you get home, you only want two rooms warming, the kitchen and living room, boiler minimum output is 8 kW, so the living room and kitchen radiators need to between then deliver 8 kW into the rooms, so kitchen a couple of kick space fan assisted and living room a pair of very large radiators so it can re-heat those rooms fast, and an Opentherm controlled boiler can run very efficiently.
But if the home has small radiators then all this cleaver controls will not work, if the radiator with a return temperature of 40°C takes 3 hours to reheat the house, then it does not matter if the boiler is the best designed, you can't run at 40°C return temperature then the boiler will not run efficient, but in the main what is important is minimum output rather than maximum output, likely most homes only need 10 kW however at 10 kW the taps would be rather slow, so we look at around 25 kW so we have enough DHW even though with all the insulation in a modern home will only need 12 kW to heat it, and around 3 kW to maintain it.
So I will give an example, out all day, no fixed time for return, and the geofencing thermostat picks up you are returning one hour before you get home, you only want two rooms warming, the kitchen and living room, boiler minimum output is 8 kW, so the living room and kitchen radiators need to between then deliver 8 kW into the rooms, so kitchen a couple of kick space fan assisted and living room a pair of very large radiators so it can re-heat those rooms fast, and an Opentherm controlled boiler can run very efficiently.
But if the home has small radiators then all this cleaver controls will not work, if the radiator with a return temperature of 40°C takes 3 hours to reheat the house, then it does not matter if the boiler is the best designed, you can't run at 40°C return temperature then the boiler will not run efficient, but in the main what is important is minimum output rather than maximum output, likely most homes only need 10 kW however at 10 kW the taps would be rather slow, so we look at around 25 kW so we have enough DHW even though with all the insulation in a modern home will only need 12 kW to heat it, and around 3 kW to maintain it.
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A combi boiler may not be the best option for your house and life style.
As Eric has pointed out a combi has to be high power ( 25kW or more ) to get a reasonable flow of hot water to one shower or tap while only needing 3 kW or less to keep the house warm.
Few boilers can have that range of output and those that do may not be very efficient over the entire range.
As Eric has pointed out a combi has to be high power ( 25kW or more ) to get a reasonable flow of hot water to one shower or tap while only needing 3 kW or less to keep the house warm.
Few boilers can have that range of output and those that do may not be very efficient over the entire range.
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