The 93deg flue elbow is suitable for condensing boilers only. Here’s more information about why we should look into. Baxi boiler main system boiler 24he. The combi boiler is connected to your mains water supply and heats the water directly so when you turn on a hot tap or switch your heating on, the water flows through the boiler and heats its built in heating element this means you have no need to store hot water, as it’s there when you need it! Asbn 18kw 3 phase output connection.