F
flappy8
Hi All,
I’ve had a couple of people in to quote for boiler install with weather compensation in a well insulated refurbishment. It will be a system boiler on a 250L unvented tank with rads upstairs and UFH downstairs. I’ve done the heatloss calcs from the CIBSE book and run through the whole house boiler sizing calculator from the BRE data.
I get 13kw (inc 2kW hot water allowance) from the whole boiler method and 13.5kW from the CIBSE calcs. Similar result from the BAXI website calculator too.
Both people have said I should have a 30kW system boiler as ”that’s what you use on this size house” and that the hot water tank can use a lot of power. I’m concerned that as the boiler will only modulate down to 5kW, when it’s not deep midwinter it will end up cycling a lot and then not running efficiently. I also see a lot of stuff on the web about boilers being oversized. Has the 2kW heating allowance that gets mentioned a lot not caught up with modern cylinders?
All comments welcome.
I’ve had a couple of people in to quote for boiler install with weather compensation in a well insulated refurbishment. It will be a system boiler on a 250L unvented tank with rads upstairs and UFH downstairs. I’ve done the heatloss calcs from the CIBSE book and run through the whole house boiler sizing calculator from the BRE data.
I get 13kw (inc 2kW hot water allowance) from the whole boiler method and 13.5kW from the CIBSE calcs. Similar result from the BAXI website calculator too.
Both people have said I should have a 30kW system boiler as ”that’s what you use on this size house” and that the hot water tank can use a lot of power. I’m concerned that as the boiler will only modulate down to 5kW, when it’s not deep midwinter it will end up cycling a lot and then not running efficiently. I also see a lot of stuff on the web about boilers being oversized. Has the 2kW heating allowance that gets mentioned a lot not caught up with modern cylinders?
All comments welcome.
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