Does the Myson T4R Standard suit an open-vented system?

Yes — Myson TRVs work on both sealed and open-vented UK heating systems up to 110 °C.

Factory calibrated to 20 °C at setting '3' on the Myson T4R Standard. Re-check with a room thermometer after 24 h.

Should I fit a bypass?

Yes — always fit an ABV or a designated bypass loop to prevent pump dead-heading when all TRVs close.

How to Fit a Myson T4R Standard TRV (UK)

The valve

The Myson T4R Standard is a UK-standard 15 mm TRV with a removable sensor head. Confirm the valve body (angled or straight) matches your existing pipework before ordering.

Drain the radiator

Close the lockshield and old TRV. Loosen the radiator union at the tail. Drain 1–2 L into a shallow tray. Fit the Myson T4R Standard body with new PTFE (10 turns) and torque to 20 Nm.

Fit the head

Push the Myson T4R Standard head onto the valve pin with the digits facing outward. Rotate to '*' frost setting first to seat the wax element.

Bidirectional flow — the Myson T4R Standard accepts flow in either direction.
Horizontal head orientation — never mount vertically or wax response is skewed.
Balance the system after fitting all TRVs — set lockshields for 11 °C DT.

Frequently asked questions

Does the Myson T4R Standard suit an open-vented system?: Yes — Myson TRVs work on both sealed and open-vented UK heating systems up to 110 °C.
Head calibration?: Factory calibrated to 20 °C at setting '3' on the Myson T4R Standard. Re-check with a room thermometer after 24 h.
Should I fit a bypass?: Yes — always fit an ABV or a designated bypass loop to prevent pump dead-heading when all TRVs close.