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Heating · Radiator ControlsThermostatic Radiator Valve Installation
Thermostatic radiator valve installation gives each room its own temperature control on a single-zone radiator system, with no new piping and no wiring. Each valve senses the air around it and throttles its own radiator. Fit them on every radiator except the one in the room with the main thermostat, and add a bypass or a pressure-regulating circulator so the pump is never pushing against closed valves.
A thermostatic radiator valve, or TRV, replaces the hand valve on a radiator. Its head holds a wax or liquid element that expands as the room warms and pushes the valve closed, then relaxes and lets it reopen as the room cools. There is no battery and no wire. The dial is numbered instead of marked in degrees, and the middle setting corresponds to roughly 20°C on most makes.
The usual reason to fit them is a house with one thermostat and a dozen radiators. The thermostat sits in the hall or the living room and runs the boiler until that one spot is satisfied, while the south bedrooms overheat and the spare room is heated for nobody. TRVs let each room cap its own temperature. They can only reduce heat, though: a room that never gets warm has a flow, air or sizing problem, and that is radiator balancing or repair work.
Two rules keep a TRV system working. First, the radiator in the room with the main thermostat keeps a plain valve left open; a TRV there would close that radiator before the thermostat is satisfied, and the boiler would never be told to stop. Second, the water needs somewhere to go when most valves have closed. That means a differential-pressure bypass valve near the boiler, or a pressure-regulating circulator that slows as the valves close, in place of a fixed-speed pump whistling against shut valves.
Whether TRVs suit your house depends on the piping. Two-pipe systems take them readily. One-pipe systems with diverter tees need a low-resistance valve body made for that layout, and a series loop cannot take them without a bypass at each heater. One-pipe steam is a different product again, with the thermostatic part fitted at the air vent. We check the piping and the pump before quoting; the heat source is covered under boiler repair, and you can ask for a quote here.
TRVs are worth fitting when
- One thermostat runs the whole house and the upstairs bedrooms overheat
- Rooms on the sunny side get hot while the north side is only just comfortable
- A guest room, office or finished basement is heated all winter and rarely used
- The old hand valves are seized or leaking and have to be replaced anyway
- The boiler or circulator is being replaced and the system is already drained
How it works
Piping layout, valve sizes, angle or straight pattern, the circulator type and where the main thermostat sits. We also check whether each old valve's tailpiece will come out of the radiator, since TRV bodies come with their own.
The system is drained to below the radiators, each old valve and its matched tailpiece is removed with a spud wrench, and the TRV body is fitted with its head horizontal and clear of curtains. Seized manual valves on the remaining radiators are replaced on the same drain-down.
The bypass valve or the new circulator goes in, the system is refilled, bled and balanced, and each dial is set to a starting position. You are shown how the numbers behave so the settings can be adjusted through the first cold week.
Common questions
What does thermostatic radiator valve installation cost?
It is priced per house, not per valve, because the fixed part of the job is the drain-down, refill and bleed, and the variable part is the number of radiators, how many old tailpieces fight coming out, and whether a bypass valve or a new circulator is needed. Doing every radiator on one visit costs far less per valve than doing three now and five later. Our pricing covers the bands we publish.
Do TRVs work with a smart thermostat?
Yes. The wall thermostat still decides when the boiler fires, and the TRVs trim each room below that. Set the thermostat for the room it sits in and let the valves hold the bedrooms a little cooler. A smart thermostat adds scheduling for the whole house; the TRVs add the room-by-room part it cannot do alone on a single zone.
Why is a radiator cold with its TRV turned right up?
The valve pin is probably stuck. After a summer held closed, the small pin under the head can stay down when the head releases it, so the radiator stays shut whatever the dial says. Unscrewing the head and working the pin free usually restores it. If the pin moves and the radiator is still cold, the cause is air or flow, not the valve.
Where should the valve head sit?
In free room air: horizontal, pointing away from the radiator, not behind a curtain, a sofa or a radiator cover. A head boxed in by any of those reads the trapped heat and shuts the radiator early, so the room runs cold. Where a radiator is enclosed, the answer is a head with a remote sensor on a capillary tube, mounted on the wall beside it.
Can my seized hand valves be replaced on the same visit?
Yes, and it is the sensible time. Once the system is drained, a valve that has not turned in thirty years is the same amount of work whether it gets a TRV or a new manual valve. Any radiator you are leaving on manual, including the one in the thermostat's room, gets a working valve in that drain-down. See radiator repair for leaks and stuck valves on their own.