On 11/20/2012 9:47 AM, diydave123 wrote:
I've just had a new Vaillant EcoTec 831 boiler fitted with a Salus St620
Programmable Thermostat. Read the instructions, programmed it as
described to come on for an hour in the morning and a couple of hours in
the evening - tootled off to bed. Woke up at 1am with the boiler
cranking out heat like something possessed. Re programmed it, using 24
hour clock - same thing. Can't understand it. The instructions are
simple enough. There's nothing obvious that's wrong.

what did the installer say when you called them?