Thermostatic Radiator Valves: Models and Prices

Thermostatic radiator valves (TRVs, also called radiator thermostats) sense the room temperature and automatically adjust the amount of hot water entering the radiator; each room is kept at its own temperature, and sunny or rarely used rooms are not heated unnecessarily. This category includes Danfoss, Honeywell, ECA and KAS valve bodies, thermostatic heads, head + body sets, compact radiator valves and return valves.

Valve bodies come in angle, straight, horizontal angle and right/left double-angle versions, mostly in DN15 (½″) and DN20 (¾″) sizes. How to match the body and head to your system is summarized in our selection guide; for centrally heated buildings, also see the models with a 15 °C lower limit.

How to Choose a Thermostatic Radiator Valve

Four things determine the right valve: the connection style of the body, its size, the type of heating system and the head that will be fitted to the body. If you are replacing an existing valve, simply note the type and size of the old body; if you are only replacing the head, note the brand and connection of the body.

Body type: angle or straight?

Angle (corner) bodies are used when the pipe reaches the radiator at a right angle from the floor or wall; straight bodies when the pipe comes in level with the side of the radiator. Horizontal angle and right/left double-angle bodies are for tight spaces and special connection directions. On bottom-connected compact panel radiators with integrated valves, instead of a separate body you use the valve insert inside the radiator (Danfoss BIV) and the H-block valve underneath (Danfoss VHS-UN, RLV-KB, ECA TRV4, KAS compact valve).

Size: DN15 or DN20?

Most panel radiators use a DN15 (½″) body. DN20 (¾″) and DN25 (1″) bodies are for cast-iron radiators, large radiators and high-flow circuits. The size is determined by the connection size of the radiator and the pipe. For connection to PEX and multilayer pipe, this category also includes PEX-connection bodies (ECA Pex angle and straight, KAS 16×2 Pex-B) and compression fittings.

System type: presettable or dynamic?

Choosing the head: connection compatibility

The head must match the connection of the body: Danfoss RA series bodies use the Danfoss RA snap-on connection, while Honeywell bodies use an M30×1.5 threaded connection. The Honeywell Thera-2 head and the Danfoss ECO 2 and Honeywell HR90 electronic heads can be fitted to either connection with an adapter.

• Liquid-filled mechanical heads (Danfoss RAX, Danfoss Tilde Regus, Honeywell T4111): no batteries required, with frost protection; Danfoss RAX and Tilde have a setting range of 8–28 °C.
• Heads with remote sensor (Danfoss Tilde Redia): measure the actual room temperature where radiators are hidden behind curtains, furniture or radiator covers.
• Electronic and programmable heads (Danfoss ECO 2 Bluetooth, Honeywell HR90, Honeywell evohome HR924): run on a day-and-time schedule; ECO 2 is controlled from a smartphone, evohome from its system controller.
• Colored and designer models: Danfoss RAX black, white and chrome heads; Honeywell Therafix designer chrome bodies.

TRV Numbers: What Temperature Does Each Setting Mean?

Mechanical heads usually show a snowflake (❄) and the numbers 1 to 5. On Danfoss RAX and Tilde (Regus) heads the setting range is 8–28 °C; the settings are about 4 °C apart, and the middle setting 3 corresponds to about 20 °C:

Values may vary by model; the exact values are given on the product page and in the user manual (e.g., the range of ECA heads is +5…+30 °C). For recommended temperatures room by room and setting tips, see our thermostatic radiator valve guide.

Thermostatic Radiator Valves in Centrally Heated Buildings

In many countries, building energy rules require room temperature control in centrally heated buildings, often together with consumption-based heat cost allocation; the details differ, so check your local regulations. In Türkiye, for example, the national heat cost allocation guideline specifies thermostatic radiator valves compliant with EN 215 with a 15 °C minimum temperature setting for these buildings. If you need a head with the lower limit fixed at 15 °C, the Danfoss Tilde Regus 015G3695 is a model that meets this requirement.

With consumption-based cost allocation using heat meters or heat cost allocators, the thermostatic valve directly links how an apartment uses heat to its heating bill. For details, see our articles on the 15 °C minimum heating limit and central heating cost allocation.

Hydraulic Balancing and Return Valves

For a thermostatic valve to work properly, the system must be hydraulically balanced; in an unbalanced system some radiators do not heat up sufficiently even with the valve open. Radiator return valves (Danfoss RLV-S, RLV-CX chrome), fitted to the return end of the radiator, are used to shut off and drain the radiator and to adjust its flow. In large buildings, dynamic balancing valves are used at risers and apartment inlets; for domestic hot water, see thermostatic mixing valves, and for room control in apartments with individual boilers, see room thermostats.

Wholesale and Project Supply

We supply thermostatic radiator valves in volume to property managers of residential complexes and apartment buildings, contractors and installers. For quantity-based pricing, fill in the Wholesale Order form on the product page or message us on WhatsApp at +90 555 005 99 84. Export prices exclude Turkish VAT. Import duties and taxes in your country are paid by the buyer.

Frequently Asked Questions

Can I buy the TRV head and body separately?

Yes. The body is fitted to the radiator’s inlet connection, and the head sits on top of the body. You can replace just the head without removing the body; make sure the head has the same connection as the body (Danfoss RA or M30×1.5). If you want both, choose a head + body set.

What temperatures do the numbers on a Danfoss TRV correspond to?

On Danfoss RAX and Tilde (Regus) heads the setting range is 8–28 °C: the snowflake is about 8 °C (frost protection), 3 is about 20 °C and 5 is about 28 °C, with about 4 °C between settings. Exact values vary by model.

What is the difference between presettable and non-presettable TRVs?

On a presettable body, a presetting ring limits the maximum flow that can reach the radiator; in two-pipe systems this stops radiators close to the boiler from overheating while distant ones stay cool. A non-presettable (fixed-capacity) body has no such limit; the valve responds only to room temperature.

Should I buy an angle or a straight TRV?

If the pipe reaches the radiator at a right angle (from the floor or wall), you need an angle body; if it comes in level with the side of the radiator, you need a straight body. If you are replacing an existing valve, choose a body of the same type and size (usually DN15, ½″).

Are thermostatic radiator valves mandatory in centrally heated buildings?

It depends on local regulations. Many countries require room temperature control and consumption-based heat cost allocation in centrally heated buildings, but the details differ; in Türkiye, for example, thermostatic radiator valves compliant with EN 215 with a 15 °C minimum temperature setting are required. Check the rules that apply in your country.

Which is the best thermostatic radiator valve?

There is no single “best” model; what matters is a body that suits your system type (presettable, dynamic or one-pipe), a head that is compatible with the body, and EN 215 compliance. In this category, Danfoss is represented with a wide choice of bodies and heads, Honeywell with Thera heads and designer bodies, and ECA and KAS with angle, straight and compact models.

What setting should a TRV be left at in summer?

Outside the heating season, leaving the head at the highest setting (5, fully open) helps prevent the valve pin from sticking in the closed position.