st6400c

The CH+HW system in my new home has a programmable room stat (a Honeywell CM921) downstairs and a 7 day programmer (a Honeywell ST6400c) upstairs in the airing cupboard housing the HW cylinder. I'm wondering how best to set the CH on periods for the times I choose. For example, is it best to...

Hello all, Now that I’ve had an unvented cylinder fitted, I’m considering having a Google Nest (3rd Generation) thermostat fitted. I’ve read a few threads on here by others who also wanted to replace a Honeywell ST6400C controller (with room thermostat, hot water cylinder thermostat and a heat...