It's not suitable, even if it was a 2014 model, his best bet is to not fit it, if he won't listen to people in here, take the fooking manufacturers advice and buy the boiler you need.
It is totally suitable. It modulates down to less than his heating demands.
Other than stating its a 5bed mid terraced house care to point me where he's actually told us his heat loss figures?
If he needs 12kw at minimum load then it's not his heating system that needs upgrading.
Youre very deffient he should fit it, were you the chump that sold him the boiler, what's up escape from nurse and steal it out the plant room of the home your in?
Stick to bridging headers together cos you don't have a clue about sizing this one, that said seems you don't have a clue about headers either.
You do not have clue about boilers that modulate. It modulates down to less than his heat requirements.
That means it is suitable. Not fitting this boiler, which he got for buttons, is rather foolish.
Installing a 35mm header as I have described will make it more than suitable guaranteeing the minimum flow through the boiler at all times.
I question the design capabilities of all here. Being a hands on plumber is very different to design. Hands on plumbers only go on one system and/or boiler they know sort of works. "Yerrr Guv I only fit a Vaillant and unvented cylinder"..."what's a header Guv?" "all combis don't work Guv", etc, etc, etc, drone, drone, drone.