Boiler replacement advice required

[DaveTT]

Current Boiler
Potterton Suprima 80HE
23KW
80BTU
85% efficiency
5-bedroom house 4 bathrooms (built 2007)
24 radiators (mainly small).
200 litre water cylinder
Worked fine for heating and hot water.

Looking at replacing the boiler with a:
Worcester Bosch Greenstar 27i Gas System Boiler
92BTU
27KW
90% efficency.

Any expert opinions or advice appreciated.
All information suggests the boiler capacity would not be adequate for the size of house but it is a more capable boiler with higher output than the one I already have.

 

[flameport]

What is wrong with the current boiler?

What is the heat loss of the building - or the output of the radiators?

 

[MNW67]

A lot might depend on your hot water requirements. Whether you use multiple bathrooms at the same time and how quickly you need to replenish the cylinder. Do you know how powerful the coil in the cylinder is?

The actual central heating requirement might only be something like 6KW.

 

[DaveTT]

Current boiler fan has failed due to the flu dripping water on it as the flu has corroded and the secondary heat exchange is leaking this drips onto the ignitor that failed last week after I replaced it the PCB board then failed I have kept it alive as long as I can, it is 18 years old time for new one.
I am not sure of the radiators output will have to do a bit of research.
I have know idea of the heat loss of the building but it is very efficient I have 3 oil filled electric rads on at the moment and the house is very warm
The cylinder coil rating is 24.3KW

 

[flameport]

I have know idea of the heat loss of the building but it is very efficient

You need to find out.
Otherwise any boiler sizing is entirely by guessing, and is likely to result in something which is unsuitable.

All information suggests the boiler capacity would not be adequate for the size of house

With no heat loss data, what is this information suggesting it's too small?