In the absence of any information re the sourcing of a PTT1, I have purchased a PTT2. I have discovered that the feed to the motorised valve in the airing cupboard is indeed a permanent live.
I have one of these on my hot water cylinder and it has lost its calibration.
It is a discontinued product and has been replaced by model PTT2, which requires a live feed to run it, to which I don't have easy access in my airing cupboard.
Does anyone know from where I can still get a PTT1...