How must we determine boiler capacity in central system?

When the capacity of the new boiler located in the building to use natural gas is to be detected, one must first examine the capacity of the old boiler, if any Along with that, you must also calculate the number of radiators in the building and water volume, and check whether the current coiler capacity complies. Should there be heating problem in the building, you must make heat loss calculation and select boiler complying with this capacity.