Thermostatic radiator valve fitting in Macclesfield

A TRV is a self-contained control: a sensor head containing wax or liquid expands as the room warms and closes the valve, cutting flow to that radiator. It costs nothing to run, needs no wiring, and it stops you heating a spare bedroom to the same temperature as the living room simply because the hall thermostat has not been satisfied yet.

There are two rules for fitting them that are frequently broken. First, do not put a TRV in the same room as the main room thermostat — the two controls fight each other, with the TRV closing the radiator and the thermostat then keeping the boiler running to satisfy a room that can no longer heat. Second, at least one radiator should be left without a TRV, or a bypass provided, so there is always a path for flow when everything else has closed.

TRVs seize, and it is the single most common heating fault in an older house. The pin under the head sticks in the closed position after a summer of not moving, and the radiator stays cold in October. Often it frees with gentle persuasion; where the valve body has corroded, replacement is a short job. Exercising the heads a few times over the summer prevents most of it.

Replacing a valve traditionally meant draining the system. Modern practice uses freezing kits or specialist tools that let a valve be changed with the system full, which turns a half-day job into an hour and avoids introducing fresh oxygenated water into the system.

Smart TRVs are the natural extension: individually programmable heads that let rooms be scheduled independently and controlled from a phone. They earn their keep in larger houses with rooms used at different times, and rather less in a small flat where one thermostat does the job.