In the following article, we will introduce the subject of controlling the temperature of water heating using valves with a thermostatic head. This is a simple and long-used system, but better understanding of its elements and operation will allow you to better select devices for your needs, or better use the devices you already have. After all, the point is to reduce the cost of heating without worsening the comfort in your home.
A typical central heating radiator has valves: supply and return, and on the supply valve a knob-head that controls the inflow of heating water. If it is only a knob, we are talking about a radiator valve, if the knob contains a sensor and a valve control element - then we are dealing with a thermostatic head.
Check out thermostatic radiator valves at the Onninen wholesaler
What is a radiator valve?
There are two types of valves in a radiator: a valve on the water supply side of the radiator and a drain (return) valve, through which cooled water returns to the heating water circuit. A supply radiator valve is a simple device that regulates the flow of hot water to and from the radiator, which affects the room temperature. There are two types of valves: manual and thermostatic radiator valves (TRV). Currently, the use of thermostatic valves in multi-family buildings is required by building regulations. Thermostatic valves can be installed on all types of water radiators, without the need for special adaptations.
How to distinguish a manual valve from a thermostatic valve (TRV)?
Manual valves usually have a small, unmarked knob with no mechanisms inside, while thermostatic radiator valves have markings such as a scale, plus and minus (or on/off), indicating the direction in which it should be turned to open or close, and sometimes also visible or hidden elements that limit the minimum and maximum setting. Replacing a manual valve with a valve with a thermostatic head will allow you to adjust the room temperature to ensure better comfort, save energy and reduce CO2 emissions.
In addition to its function of cutting off the radiator outlet, the return valve is often also used to limit the flow – hydraulic balancing – so that all radiators in the system heat up at approximately the same rate. In other words, the radiator closest to the boiler would heat up faster than the one at the other end of the house, which is why the balancing valves should be opened more and more the further away the radiator is from the boiler (heat source). The balancing function is often also implemented in the supply valve by the so-called “pre-setting”, which is a type of orifice that limits the flow through the valve.
Recently, more advanced valve solutions have also appeared – the so-called: "dynamic thermostatic valves" or "pressure-independent thermostatic valves" where the flow limitation is not set once but dynamically changes depending on the pressure in the heating system. This excludes the influence of pressure fluctuations on the heating system balance, which means the system provides higher comfort of use and additional savings. The element necessary for the operation of a thermostatic valve is the thermostatic head.
What is a thermostatic head?
A thermostatic head is a device mounted on a radiator that allows you to automatically regulate the flow of hot water to that radiator. The head controls the thermostatic valve and increases or decreases the flow of hot water to the radiator depending on the ambient temperature. The valve is open until the room reaches the desired temperature. If the temperature drops again, the valve opens again.
The main element of the thermostatic head is the "engine" controlling the valve, containing a specific thermostatic liquid or gas ("gas head"). This liquid expands or contracts depending on the room temperature. If the room temperature is higher than the set (e.g. 20 ° C) on the valve, the thermostatic liquid will increase in volume, causing a change in the length of the cylindrical regulator in the form of a bellows filled with liquid or gas, closing the valve, which in turn reduces the flow of hot water to the radiator. If the ambient temperature is lower than the set temperature, the reverse process takes place and the valve opens and the radiator heats up.
Advantages of Thermostatic Heads
Thermostatic valves help reduce losses and improve comfort by stabilising the temperature in each room according to the requirements of the resident. Thermostatic valves are currently required by building regulations, which impose the obligation to use valves with a minimum temperature limit of 16°C in multi-family buildings so that an empty apartment cannot have the heating completely closed because this could cause the premises to cool down and such unfavourable phenomena as the accumulation of moisture, the development of fungi or mould in the walls.
Correct use of thermostatic heads
The thermostatic head should not be covered because as a temperature sensor it should detect the temperature inside the room and not in a closed space by the radiator. Remove everything that prevents normal air circulation around the radiator (curtains, furniture, radiator covers, shelves). Remove all heat sources from the vicinity of the head (such as cookers or ovens). If the location of the head is very unfavourable - you can use a head with a remote sensor, which can be moved away from the head knob by the length of the connecting capillary - usually 1 - 2 metres.
Close the valve when you have open doors or windows, keeping the windows open while turning on the heating system wastes a lot of heat and money! In summer, leave the valve fully open at the highest temperature position to avoid scale formation and blocking of the thermostatic valve. In rooms that are not in use or when leaving the house for a few days, leave the valve open at half range.
What should you consider when choosing a radiator thermostat for your home?
When buying new thermostats for radiators or underfloor heating, the decision can be difficult due to the wealth of offers on the market. Below are the most important selection factors to consider when making a decision.
- The system, type or brand of thermostats you have - in the case of supplementing the installation, it is worth considering the same brand or type of connections. Especially with remotely controlled electronic heads .
-
Type of connection to the radiator - the most popular systems in Poland are: Danfoss RTD-N (produced until 2010, but there are substitutes for this system on the market) Danfoss RA-Click; M30x1.5; M28x1.5 - when replacing heads, the new heads must fit the existing valves. - Quality of regulation – important parameters are: reaction speed, regulation accuracy (hysteresis),
- Additional functions - frost protection, remote measurement, and in electronic heads also open window detection, "vacation" function, valve blocking protection, programming options,
- Aesthetics – colours, shape, decorative finish matching the interior,
- Ergonomics – clear markings, scale in degrees C, setting limiters, for electronic heads: possibility of programming, remote adjustment,
- Finally, the price - if we have a limited budget, this may be an important determinant, but looking at the above factors - the initial purchase price is not everything - heads offering better regulation over 10-15 years of use may turn out to be much cheaper in the use of a home heating system.
If in doubt, it is always worth consulting a specialist – an installer or a qualified seller.