There are thousands of Drayton TRV3 thermostatic radiator valves installed on radiators in businesses and homes. Each one of these has a Drayton manually-operated TRV head.

However, you run into trouble when you want to replace the head with a modern computer controlled one, connected to a BMS or similar system. The TRV3 has a nonstandard proprietary thread of around 26.5mm diameter, and this does not fit any of the automation TRV heads on the market.

Now, you could replace the TRV body to get over this problem but this involves isolating the radiator or draining down the system and some other plumbing work – which will costs and is a bit of a bind.

The alternative is but buy a HS-TRVD-AD which allows any modern M30 threaded TRV head to be used with a Drayton TRV3 valve body. The alternative is to buy a TRV4c TRV Head from Drayton, rrp £45, or drain down and replace the complete valve body.

Made from brass, the inexpensive HS-TRVD-AD securely fits the TRV-3 whilst the broad high tensile steel pin provides a perfect mechanical transmission of the automation force through to the TRV body pin.