vailiant turbomax 828e modluation problem

[zx6rninja]

hi i have a vailiant turbomax 828e i have a problem with the ch with the heating set to any temp it always seems to modulate 4-5 degrees below set point and not meet set point and shut down.

with a set point of 82 degrees gas valve opens to 1.9mb ignition rate then opens to 9.8mb full rate but as it reaches 70 degree flow temp the gas valves backs off until it reaches 3-4mb then the boiler maintains a flow rate of 78 degrees not 82 as set thus the boiler never reaches set point and shuts down

 

[picasso]

Are you an RGI ?

 

[zx6rninja]

Yes but I only work on commercial stuff like CHP engines and industrial boilers I currently maintain the CHP engine and boilers at a prison.

My knowledge of domestic stuff is limited
I'm currently thinking it's either the gas valve or the PCB

 

[ianmcd]

Personally I wouldnt think it is either if you are GSR join the CC and I will tell you what I think it is and if I am wrong plenty of experience in ther will help you out no problem