How to Set the Thermostatic Valve to the Correct Temperature
How to set the thermostatic valve to the correct temperature – a complete practical guide
The thermostatic valve is one of those components of the heating system that most people set once, forget about it, and then wonder why it's either too cold or unnecessarily warm in the room. Yet, correctly setting the thermostatic valve is one of the simplest and most effective ways to save energy – without any investment in a new boiler, smart thermostat, or other expensive technology. In this article, we will go through the entire topic from the basics to advanced settings, including practical experiences from installation practice.
What a thermostatic valve actually does – principle of operation
Before we get into the actual setting, it is good to understand what happens inside the valve. A thermostatic valve is not an active device – it has no motor, electric drive (in the basic mechanical version), or batteries. It works purely on the principle of thermal expansion.
Inside the valve there is a sensing element – either filled with liquid or gas (more about the difference between these is in the article Thermostatic valve: liquid vs. gas – which is better). When the temperature in the room rises above the set value, the filling expands, the piston pushes on the valve cone, and the flow of hot water through the radiator is narrowed or completely stopped. When the temperature drops, the filling contracts, the piston spring is released, and the valve opens again.
Result: the radiator self-regulates according to the room temperature, not according to how hot the water is coming from the boiler. This is the essence of the whole system.
Scale on the thermostatic valve – what the numbers mean
On every thermostatic valve you will find a scale – usually numbers from 1 to 5, sometimes with intermediate steps (1.5 – 2 – 2.5 and so on), and often special symbols at both extreme positions. Many people mistakenly believe that the numbers directly indicate temperatures in degrees Celsius. This is not the case – it is a relative scale, the actual value of which depends on the manufacturer and the specific model.
As approximate values, the following conversion applies for most European manufacturers (Danfoss, Heimeier, Oventrop, Herz and similar):
| Position / number | Approximate room temperature | Typical use |
|---|---|---|
| * (star/snowflake) | 5 – 7 °C (anti-frost protection) | Unheated storage, basement, garage, long-term absence |
| 1 | 10 – 12 °C | Spaces with minimal occupancy (basement, hallway), night reduction |
| 2 | 16 – 17 °C | Bedroom, hallway, less frequently used room |
| 3 | 20 – 21 °C | Living room, dining room, office – standard comfortable temperature |
| 4 | 24 – 25 °C | Bathroom, children's room, room with higher comfort temperature |
| 5 | 28 – 30 °C (maximum) | Maximum flow – fully open valve, only occasionally |
Important practical note: These values are approximate. The actual temperature at which the valve closes depends on the location of the valve, air flow, solar radiation, and also on the quality of the sensor itself. Therefore, always fine-tune the setting according to the actual feeling in the room – not blindly according to the table.
Step by step: how to correctly set the thermostatic valve
1. Let the room reach its natural temperature
Before setting, it is good to know at what temperature you want to heat the room. For example, if you want to maintain 21 °C in the living room, use a thermometer (a regular digital home thermometer is sufficient) to determine the current air temperature in the center of the room at a height of about 1 to 1.5 meters from the floor – not near the window, not near the radiator.
2. Set the valve to position 5 (fully open)
Let the radiator run at full power. Wait until the room heats up to the desired temperature (or 1–2 °C higher). If the temperature just reaches the desired 21 °C, proceed to the next step.
3. Set the number corresponding to your desired temperature
For 21 °C, turn the head to position 3. The thermostatic head will now start limiting the water flow when the room temperature reaches this level. The system will maintain the temperature automatically.
4. Check and fine-tune after 24–48 hours
During the following two days, monitor the temperature with the thermometer. If the room is warmer than you want, turn the head half a step toward the lower number. If it is colder, turn it toward the higher number. This fine-tuning is common in practice – the actual response depends on the room's heat loss, size, radiator output, and other factors.
5. Record the setting
It sounds trivial, but from practice I know that most people forget how they had the heads set after the summer, when the system is turned off. Record the optimal position for each room – it will save you from fumbling during the next heating season start-up.
Recommended temperatures for individual rooms
One of the most common questions in practice: "What should I set the head to in the bathroom, bedroom, or hallway?" Recommended values are based on a combination of hygiene standards, energy efficiency, and practical experience:
- Living room, dining room: 20 – 22 °C → position around 3
- Bedroom: 16 – 18 °C → position 2 to 2.5 (a cooler bedroom supports good sleep)
- Children's room: 20 – 22 °C → position 3 (up to 22 – 24 °C → position 3.5 for infants)
- Bathroom: 22 – 24 °C → position 3.5 to 4 (bathrooms often have an electric heater that supplements the heat)
- Kitchen: 18 – 20 °C → position 2.5 to 3 (appliances and cooking generate heat themselves)
- Hallway, entrance: 15 – 18 °C → position 2 (nobody stays here for long)
- Study / office: 20 – 21 °C → position 3
- Unheated space, storage room: 5 – 7 °C → position ❄ (anti-frost position to prevent pipe freezing)
For every additional 1 °C above the recommended temperature, heating costs increase by 6 – 8 %. This means that if you have an unnecessary 24 °C instead of 21 °C in the living room, you will pay 18 – 24 % more. Year after year. I have seen this number confirmed on the bills of several households after we correctly set the heads – saving 15 – 20 % without any further investment is realistic.
Common mistakes when setting the thermostatic head
Mistake No. 1: The head is covered by curtains or furniture
This is by far the most common problem I encounter with customers. A curtain hangs in front of the radiator, furniture is placed very close to it – and the thermostatic head's sensor measures the temperature of the air trapped behind the curtain, not the room temperature. Result: the room may actually be 21 °C, but the head "sees" 26 °C near the radiator and closes the valve. The radiator does not heat, although it should.
Solution: either shorten the curtain above the level of the radiator or use a thermostatic head with an external sensor (a remote sensor on a capillary tube), which is placed freely in the room.
Mistake No. 2: Setting to 5 for the entire season
Quite a few households leave the heads at position 5 (maximum) and control the temperature exclusively at the boiler. This is energy inefficient – the boiler must generate heat for all rooms equally, although for example, the hallway does not need 25 °C. Every head in position 5 means the valve is fully open and no regulation is taking place.
Mistake No. 3: Setting to 0 or fully closing when leaving the house
When going away for the weekend, many people turn all the heads to zero (fully closed valve). This is problematic for two reasons: first, the pipes may cool to a critical temperature (risk of freezing in extreme cold), second, when you return, the system will consume more energy to reheat a cold house than if it had been kept at 14 – 16 °C. The correct setting is position 1 or ❄ – not zero.
Mistake No. 4: Incorrect placement of the head
A thermostatic head works best when it is placed horizontally or in the direction specified by the manufacturer. If the radiator valve is mounted so that the head points directly upward (vertical position), the warm air rising from the radiator can heat the sensor directly and cause the valve to close prematurely. Manufacturers handle this differently – some heads have correction for vertical position, others do not. If you have a thermostatic corner radiator valve, the head is usually mounted horizontally, which is the ideal position.
Mistake No. 5: Stuck piston after the summer break
After the summer shutdown of heating, the valve piston can get stuck in the closed position due to deposits from the water. The radiator then does not heat at all, although the boiler is running. You will learn more about this issue in the article Stuck or leaking radiator valve: causes and solutions. Quick temporary solution: disassemble the head, find the piston (a small brass pin), and gently press it several times with your finger or a pencil.
Thermostatic head and energy savings – real numbers
Proper adjustment of thermostatic heads is one of the measures with the shortest payback period – actually zero, since it's just a matter of turning a ring. To illustrate, here are a few real-life scenarios from practice:
Scenario A – family house, 4 rooms, all heads set to position 4–5: The customer was paying about €1,800 per year for gas. After adjusting the heads (living room 3, bedroom 2, hallway 1.5, bathroom 3.5), consumption dropped by 22%. Annual savings: about €396. Time spent adjusting: around 20 minutes.
Scenario B – apartment, central heating, curtain in front of the radiator: The customer complained that it was always cold in the living room, even though the boiler was supplying enough heat. Cause: the curtain was blocking the head's sensor. After shortening the curtain, the radiator started to regulate properly and the room became comfortable without any changes to the boiler.
Scenario C – night temperature reduction: Lowering the temperature in the bedroom from 21 °C to 17 °C during the night (10 hours) means a reduction of about 40% in energy consumption for that room during the night. Over a year, this is a measurable saving – with a bedroom radiator of 1 kW power and a cost of €0.12/kWh, it means dozens of euros saved from just one room.
Special situations and advanced settings
Night temperature reduction – manual or automatic
Standard mechanical thermostatic heads do not have a timer – you have to turn the ring to a lower position every evening and back in the morning. For greater comfort, programmable electronic thermostatic heads are available, which have a built-in timer and allow you to pre-set different temperatures for different times. These heads can be mounted on the same type of valve as the classic ones – for example, on a direct-acting radiator valve with thermostatic control – and the installation is identical.
Rooms with floor heating
If you have floor heating and a radiator with a thermostatic head in the room, it is important that their thermostatic control does not interfere with each other. It is generally recommended to set the thermostatic head on the radiator 1–2 degrees higher than the desired temperature – the floor heating will supply the heat primarily, and the radiator will only supplement it in case of sudden cooling.
Systems with thermostatic heads and boiler with equitemperature control
In modern systems with equitemperature control, the boiler itself adjusts the temperature of the heating water according to the outside temperature. In such systems, thermostatic heads function as a "local corrector" – the boiler takes care of the coarse regulation, and the heads handle the fine-tuning, room by room. The result is the most energy-efficient possible – but only if the heads are properly set.
Larger sets and complete assemblies for new installations
If you are installing new radiators or changing the entire system, it may be advantageous to use complete sets including the valve and fittings. For example, the SWING2 PN10 set in the direct version or the SWING2 PN10 set in the corner version include everything needed for a direct connection to the radiator. The question of when it is worth buying a complete set is discussed in the article SWING2 Set: What It Contains and When It Is Worth Buying a Complete Set.
Replacement and compatibility of thermostatic head
If you need to replace an old thermostatic head with a new one, or switch from a mechanical to an electronic one, it is important to check compatibility with the valve. Most European manufacturers of heads use the M30 × 1.5 mm connection standard – this is the most common thread for thermostatic heads. Some older valves (e.g., Danfoss RA or RAV series) require special adapters.
Good news: replacing a thermostatic head is usually possible without draining the heating system. The head is mounted directly on the valve body and is held either by a thread or a bayonet lock. The whole operation takes less than 5 minutes. A more detailed procedure can be found in the article Replacing a thermostatic head without draining the system – is it possible.
If you are dealing with a more complex installation – for example, replacing the entire valve including a direct or corner version – see the articles Installing a radiator valve yourself: step-by-step procedure and How to choose a radiator valve: direct vs. corner – what matters. For understanding connection types (EK, VK), the article What type of valve connection do I need: EK, VK and other standards is useful.
Maintenance of thermostatic head – what to do every season
The thermostatic head is a relatively low-maintenance component, but some tasks are worth performing regularly:
- Before the heating season (September/October): Check that the valve piston is not stuck. Disassemble the head, press the piston and make sure it moves freely. Reattach the head, set it to position 5 and check that the radiator heats up.
- During the season: If you notice that a room is constantly too cold or too hot despite correct settings, check whether the head is mechanically damaged or whether there has been a leak of the sensor filling.
- After the heating season (April/May): Set the heads to position 2–3 (not to zero). The piston will not remain pressed for a long time and will not be prone to sticking.
- Draining radiators of air: A thermostatic head works properly only when water – not an air pocket – is flowing through the radiator. If the radiator heats only the lower third and the upper part remains cold, it is necessary to bleed it. More in the article Maintenance and bleeding of radiator valves – how and how often.
Most frequently asked questions (FAQ)
Why doesn't my thermostatic head click when adjusting – is that normal?
Yes, most mechanical liquid or gas thermostatic heads do not click when turned. The scale is continuous. Clicking could on the contrary indicate a mechanical fault. Some electronic heads make a clicking sound when switching the valve position, but this is not standard for common mechanical heads.
Can I fit any thermostatic head to any valve?
Not always. The standard thread M30 × 1.5 mm is common among most manufacturers, but there are also different standards (e.g. Danfoss RA, RAV, RAVL or Herz). Before purchasing a head, check what type of valve you have – either by the product label or by bringing a photo of the existing valve to the store. In the worst case, an adapter can be used.
What should I set the heads to when I go on a two-week holiday in winter?
Never to zero (completely closed). The correct position is ❄ (star, frost protection position) or the number 1 – a temperature of around 7 – 10 °C. This ensures that the pipes do not freeze, but you are not paying for unnecessary heating of empty rooms. After returning, set the normal values – the system will heat up within a few hours.
Why isn't the radiator heating, even though the thermostatic head is set to 5?
There can be several reasons. The most common: a stuck valve piston (disassemble the head and check the piston's mobility). Another possibility: an air pocket in the radiator (bleed it). Alternatively, there may be a problem on the boiler or supply side – check whether other radiators in the house are working normally. It could also be an issue with the system's hydraulic balancing.
Is it worth adjusting thermostatic heads in an apartment with central heating?
Definitely yes – and even more important than in a family house. With central heating and heat meters (calorimeters), you pay for the actual heat consumed. Properly adjusted heads directly reduce your consumption. In apartment buildings without individual meters, heat distribution ratios are based on the actual heat taken by each radiator – and there, correct head settings are directly financially beneficial.
How do I know that a thermostatic head is broken and needs to be replaced?
Main signs of failure: the head does not react to setting changes (the radiator is always fully hot or always cold), visible mechanical damage (cracked cover, leaked filling from the sensor – indicated by an oily stain), the sensor cannot be pressed even by hand movement. The average lifespan of a quality thermostatic head is 10 – 15 years. Replacement is simple and inexpensive – a new head costs less than a service technician's call-out fee in the standard segment.
Conclusion: a small turn, a big saving
Correctly setting a thermostatic head is one of the few things in heating where an investment in the form of just a few minutes of your time brings real and measurable results year after year. It's not rocket science – it's enough to understand what the numbers on the scale mean, what temperature is actually needed in each room, and let the system do its job.
If you are also considering choosing a valve for the head, you can look at the thermostatic valve in straight design or the VK valve in corner design – both types are compatible with standard thermostatic heads. Before installation, also read the article How to choose a radiator valve: straight vs. corner – what matters to choose the right type for your specific installation.
The thermostatic head does its job quietly, reliably and without demanding attention – but only if you create the right conditions for it: free access to room air, correct setting and annual piston check before the season. That's really all it asks of you.
Do you have a question about this topic?
Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.