@Thomp_9 If yours is a wired thermostat then you DO needs to power off - see below
When replacing the batteries, please remember:
I just click the thermostat off the wall to replace batteries. Never heard I had to switch off the boiler. The helpdesk didn't tell me to do so either when they once gave me a step by step instruction.
It looks like you're new here. If you want to get involved, click one of these buttons!