my old radiators are missing the TRV heads. Most of the ones I see fit a hex nut. My radiators have a round (plastic?) nut. What kind of TRV would fit these?
eQ-3 heads are 32 mm as standard and have a kit with them to fit other types, and auto adjust the travel to suit valve, they are electronic, I got the bluetooth version for £15 each in 2019, but may cost more now, I think the Terrier i30 is similar.
I am an electrician not a plumber, but noted the numbers 1 to 6 and the recess for a tool to engage and I seem to remember there was a combined lock shield and TRV head so is there a lock shield valve other side of radiator?
