Question: 40 kw boiler how many radiators?
Answer: As a rough guide most apartments and smaller houses, with up to 10 radiators will require a 24-25kw boiler. A 28-30kw would be installed for a medium to large 3-4 bed house with up to 15 radiators, and a 33-35kw and a 40kw would be for a large house with anything up to 20 radiators.