Radiators heating up on DHW setting

[Ranger Bob]

Since replacing the expansion vessel on our Viessman 333 gas boiler, we've experienced a major problem. When we want hot water only,(DHW) setting, the radiators are being activated! Obvious solution may be with the 3 way port, but the complete heating system is now automatically switching itself on at 5.30 every morning, as if it were the times central heating system and this is in the hot water mode! We're scratching our heads as to what is going on?

 

[Dan]

Hi, I assume you're still in contact with your plumber? How soon was this replaced?

Is this boiler in France?

 

[Ranger Bob]

Hi, I assume you're still in contact with your plumber? How soon was this replaced?

Is this boiler in France?

Hi Dan, yes am still in contact with my plumber...he’s as puzzled as I am. We’re based in France and the problem started as soon as the expansion vessel was replaced.