Considering replacing old Camray with a new unit. Have approximately 25kw of rads installed plus say 3kw for the hot water tank giving 28kw. Now the boiler is some 15 metres from the house feeding in 35mm copper insulated pipe under a lawn. In the very near future I will change this for a properly insulated twin pipe setup. Is my estimate of a 32kw or 36kw boiler enough or should I aim higher say a 36?46kw ?