I am on the verge of placing an order for a 15kW open vent condensing gas boiler, with vertical flue, and have narrowed the choice to the following:
Valliant ecoTEC plus 415 or Worcester Greenstar 15RI
Apparently the Valliant is a newer design but the Worcester (Bosch) has better construction with superior service and warranty.
Any comments based on recent experience are welcomed and will be read with interest.