Myson boiler questions

[2ptjoe]

I've got got hold of my newish house and we're doing an extension. Part of this is going to involve 2 extra bedrooms and another 4 heated rooms in total so i'm looking the Myson boiler wondering if it'll sensibly cope.
First question of course is what model it is and i cant see alot on it apart from the make and pressure jet 40 / 50 but that doesn't sound like the size to me .... is it ?

Thats first and then i'll need to work out how many aprox rads it's supply and hot water as well of course. We've a famiy of 5 .

Any thoughts on Myson and where to start ?
Thankls

 

[Tibbot]

It should mean 50K Btu output. You'll need heat loss calcs for extended house. You can't undersize with these boilers which is a shame because they were good. No longer made for years though.