Temperature Rise at Night

[tonym191]

I have room stat in hall, non try rad in hall, all other rads trv, programable controller and grundfos pump, all very much normal.
At home all day at moment so heating on from 9am to 10-30pm.
In the early evening, about sunset the temperature in the hours rises about one and a half degrees. No changes to room stat or trv's, any ideas why.
It happens consistently

 

[SimonJohns]

is your room stat in view of a window?

 

[tonym191]

No, room stat is not in view of window. Room stat is in the hall, out of site of windows. Hall rad does not have a trv, but rooms where temperature rises in evening do all have trv's.
I have been in house since new, 9 years this year, and am wondering if the system should be flushed.
Also I have checked all trv's and the "pin" is free all rads warm up to hot when trv's are set to max.
Trv's are Myson and boiler Potterton.
Wall stat is "smart" in that it has an accelerator but it is not programmable.



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