Observing thermostatic control

If the room reaches the temperature set on a thermostat - either a room thermostat or a thermostatic radiator valve - that cuts the top of the wave off. Here’s an example:

The tip-off is that the heating curve “waves” haven’t crested properly. They look like it could manage to climb higher and the temperature is being held for hours. A good thermostat will hold the temperature within a degree of the temperature that is set on it, and this is important because having a temperature that varies by more than around 2 degrees C makes people uncomfortable. In a venue that only heats spaces for an hour at a time, it can be difficult to tell.