I have my expansion tank replaced as it was full of water. There was heat for a few days and then there was no heat. . The plumber came back and replaced my zone valve model V8043G1018 and the plumber asked what temp. do I like the room temp. at ?. I replied 20 degrees C. I was not there to see him do it but I think he adjusted the room thermostat ( this is my guess). There was heat for a few days, then there was no heat. Now, the boiler does not fire up even when I adjust my thermostat to 30 degrees C. What is the problem?.