Help with new heating and hot water system!

jennifernil

Yes, I would think the next size down would be sufficient for the OP, though I do not know whether an unvented system needs more capacity than a vented, or whether the size of the HW tank is relevant?

I was more posting to say that we have found the Viessmann boilers to be very good, and for us, not significantly more expensive than the others suggested by our gas person.  We wanted something that would last many years, and had a good warranty.  The original Potterton boilers were in place for over 30 years, still worked fine but were by then inefficient.

The big boiler heats the main house, which is roughly 210 sq m, but we do have very high ceilings in the lounge, dining room and hall/stairs, with a lot of very big windows on the south facing side.  We did consider joining the 2 systems in the house, as there is no longer a granny in the flat, but in the end it proved too difficult due to the positions of the HW tanks.    It would be possible but would involve lifting a lot of flooring, which we did not want to do.    Next owners can do it if they want!