On 03/02/2011 00:20, John Rumm wrote:

I would argue that the sealed system is the one to go for in most
circumstances. Easier to implement, less space, easier and faster to
fill and bleed,

Are these of interest in my (and the OP's case) where we already have an
old Y-plan system? Isn't it easier and cheaper to just stick a Heating
Only boiler in place of the old one and be done with it?

no risk of floods if you get a leak in the heating
system etc. No sucking air into the system and no pump over. On the down
side its a tad harder to add inhibitor since you can't just log it in a
tank, but you will get less corrosion with a sealed system anyway usually.

I don't meddle with these things and I have a local technican servicing
my dinosaur annually anyway, so I guess no problem in my case.

The Vaillant ones you were looking at can also interact with a boiler
that has external temperature control.

Ah, the Vaillant looks to my untrained eye as a problem in this
department. The weather compensation module requires its matching
compensator and (I think) an additional mixer module.

This means that the boiler can
use low flow temperatures for maximum efficiency when heating the house
via the rads, but then switch to a higher temperature for reheating the
tank so as to make best use of its capacity.

Thanks for the input!

Kostas

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