As with TRV’s a room thermostat controls the temperature of the room that they are in however unlike a TRV a room thermostat switches the boiler off when the target temperature has been reached. Older room thermostats where the dial analogue type but more modern ones are now called smart thermostats. Some of the more modern smart thermostats will work out how long it takes for the house to heat up and cool and adjust the heating demand to suit. Some actually look at the weather, through your homes Wiﬁ, and will adjust accordingly, so if it is an unseasonably cold day it may adjust the heating program so the desired temperature is reached when it normally would be, and vice versa, if its an unusually warm day it may delay the time the heating switches on. Nearly all modes smart thermostat can be linked to an app on your phone to allow you to control your heating when you are not at home.
If installing a new boiler or a new heating system and no room thermostat is already present then it is a requirement that a new one be installed along with the rest of the system. Room thermostats these days can be wireless, so the room thermostats can be powered by batteries and they communicate wirelessly to a receiver that would be wired in to the boiler. This allows the room thermostat to be located virtually anywhere without the need of running new cables and chasing walls out. The wireless technology is dependent on distance from receiver and obstacles in between, e.g. thick stone walls will reduce the signals power between room thermostat and receiver.