Some Thermostatic radiator valves will come on , even if set at zero, if the room temp drops too far though. I have been called out to a few 'panic' calls over the years when a decorator or home decorator has removed a rad to paint behind and the TRV has come on overnight and flooded the place - it is always important to manually cap off a Therm rad valve if you disconnect it!Further to my ongoing Radiator problems.
The rads in the living room are now working as they should do, however this morning I walked past my daughter’s bedroom (she’s been out at Uni since 7am) and I noticed that the room was very warm. I checked the rad and it was piping hot, thinking that she had left it on before she left the house, I bent down to turn the dial down, and guess what…………..the dial was at zero.
Whatever the problem was with the rads in the living room has now moved itself upstairs to her bedroom.
I’ll have to call out the engineer again. This is costing me a bloody fortune.
Be careful also changing the top only. You can do this on most TRVs without having to drain down but unless you get exactly the right make and model it may not fit. Some like the classic original 1970s Drayton TRV have been revamped over the years with several different models and heads don't always mix. Thread sizes are nearly always different for different makes and the height of the pins and so on so only go for it if you can find the exact replacement!