Boiler options - Ideal, Worcester Bosch or Viessmann?

[JonathanM]

The 200-W is the only gas boiler sold in both UK and DE markets (the 050 and 100 are scaled down UK market only models). Apparently, the 300-W is even more advanced and borders on science fiction!

I didn't even realise there was a 300-W!

Jury is still out on reliability as it's only been 9 months since installation but I have to say I have to share that I've observed the boiler run at 10% modulation when using the UFH, during which time our gas consumption was surprisingly low for the amount of heat that was being emitted. It felt like we may be able to heat the entire property using ground floor UFH on all but the coldest of days. Fingers crossed, as this would mean a much higher % saving

I think it’s that ability to provide the gentle, super controlled heating which will produce the energy savings. It seems impossible now, to me at least, on a pure numbers basis, for any boiler to get much more efficient, because at low temperature running they are all so efficient. But it’s how controllable and how nice it feels in practice, which makes you warm even at a lower setting.

 

[JonathanM]

Yes, DHW cylinder temperature target set at 50 degrees daily with a weekly legionella cycle (similar to a heat pump). All out of the box.

I think the Alpha might be able to do that, if you fitted additional sensors, and the diverter valve kit, and the dedicated climatic controller. But not out of the box, and it all looks pretty expensive.

 

[Harry Bloomfield]

but I have to say I have to share that I've observed the boiler run at 10% modulation when using the UFH, during which time our gas consumption was surprisingly low for the amount of heat that was being emitted.

I have a Vaillant boiler and so far as I know - the only way I can tell whether and how much it is modulating, is by the amount of noise it makes and really it it mostly very quiet, or by checking my Smart Meters Indoor display's Kwh instantaneous display.

 

[Screwdriva]

I have a Vaillant boiler and so far as I know - the only way I can tell whether and how much it is modulating, is by the amount of noise it makes and really it it mostly very quiet, or by checking my Smart Meters Indoor display's Kwh instantaneous display.

Viessman displays it's current modulation % on the boiler display screen and on the app.