Do you keep it on continually? I had a nightmare with mine when we moved in, it didn't seem to heat up, we turned it off this summer, but I need to think about turning it on now to make sure it works. I turned all the thermostats back on today and set them for 21 to test it, but the boiler didn't
make a noise so I don't know it it worked or not!! The temp has reached 21 and it has clicked ...