Hi all

Looking at a replacement boiler prior to kitchen refurb and I see that
Worcester Bosch do HE28 and HE29.
The difference is, one is "system" boiler containing pump and the other
"conventional" boiler without pump.
Both I believe are condensing units so presumably meet the recent required
standards.
BUT
The system boiler appears to be used on sealed systems only!
Can someone explain why please?

I am improving (I hope) a 1970s build house.
Is it likely that the system will be "sealable". What would make it
unsuitable for sealing?
I currently have Gloworm Spacesaver 50 and pumped S plan piping (with some
naff modifications).
I am replacing all rads with Drayton TRVs and Pegler Terrier lockshields (as
I renovate each room).

Any recommendations on controls for whichever boiler is recommended?

TIA


Phil