In message , "Dave Plowman (News)"
writes
I replaced my trusty of old basic electric Potterton Kingfisher with a
Vitodens 200 system boiler some months ago. And it works just fine.

However, I miss having the external programmer of old - if I wish to
switch things off when going away etc it means going to the boiler itself.
Viessmann reckon the way round this is to use an extra external controller
- using the room stat circuit - and leave the internal one set to
constant. Which isn't really what I want. Apart from the unnecessary cost.

The integral controller has a four pin plug for everything - so I'm
assuming DC

why DC ?

The Saunier Duval programmer is 24vdc powered, but almost every other
one I've encountered is mains powered

--
geoff