How to choose a thermostat for heating radiators?
In order for the heating system to work efficiently and save your budget, it is important to strike a balance between energy consumption and a comfortable indoor temperature. There have been many ways to reach this "golden mean", but the most effective was the radiator thermostat.
Thermostats allow you to change the heat output and automatically regulate the operation of the radiators separately in each room. That is, they make sure that the radiator provides sufficient, but not excessive, heating of the rooms. The thermostats function is very simple: in response to room conditions, they increase or decrease the supply of media at the entrance to the heat transfer circuit of the device. And almost obsolete hand models completely controlled the flow by simply twisting / unscrewing the valve.
The thermostat for a radiator consists of only two parts: a brass valve and a heat sensitive head. Pure mechanics - no additional power is needed for these elements. But the design and working substance are worthy of a separate description. It is these parameters that determine the belonging of the thermostat to a specific family, as well as its effectiveness.
Types and features
Structurally, thermostats are mechanical, electromagnetic and electronic.
1. Mechanics.
The thermosensitive element of such a regulator is located in the head with a marked handle. The scale allows you to set different operating modes for heating, which will then be automatically maintained by the thermostat. Each position of the handle corresponds to a certain level of pressure of the thermosensitive body on the overlapping rod and the counter resistance of the flow in the system. When conditions in the room change, the working fluid in the head contracts or expands, displacing the stem and thereby changing the coolant flow into the radiator.
Depending on the working fluid, there are three types of thermal heads:
- Solid - contain heat-sensitive substances such as paraffin, ozokerite or stearin. Their use is considered ineffective, since the heating response speed is about 30-40 minutes, but such devices cannot be denied reliability.
- Liquid - alcohols or oil work in their heads. Such regulators are characterized by fast response when the characteristics of the heating system change. But they respond to external factors only after 20-25 minutes.
- Gas-filled - are considered more "correct", because they primarily react to the temperature difference in the room. This has been happening for 8-10 minutes.
Mechanical controls are affected by direct sunlight, a draft from a window, or other heat sources affecting the thermostat. As a result, he may misinterpret changing conditions in the room.
2. Electromagnetic.
This type of thermostat is no different from mechanical devices. Only instead of the expanding working fluid, a bimetallic electromagnetic relay is installed in its head. Strips with different rates of thermal expansion react in their own way to changes in ambient temperature and act on the shut-off valve.
3. Electronic thermostat.
This group of devices has its own classification, dividing thermostats into two traditional types: analog and digital. The latter, in turn, can be:
- With open logic - most often used in industrial facilities as central regulators. Very sophisticated, multifunctional and "smart" systems that are able to choose the optimal mode of operation themselves.
- With closed logic - the most common electronic devices in everyday life that operate on batteries.
The principle of operation of programmable thermostats for radiators is very similar to the mechanical heads already discussed in this review: the same stem that opens and closes the valve, the same sensitivity to ambient temperature. But the microprocessor is already responsible for all this, which reads the sensor measurements and sends the command to the servo. Naturally, the price for such "smart" devices is much higher.
Selection rules
To choose the right thermostat for a heating radiator, you need to take into account many of the nuances of a particular system:
- connection diagram and type of radiators;
- their distance from the heating boiler;
- coolant quality;
- features of the operation of the premises;
- climatic conditions in the region.
A mechanical thermostat for a heating radiator is also separately selected for one- and two-pipe heating systems, since the pressure on the shut-off valve in them will be different. For the first type of heating circuits, a bypass is a mandatory element, for the second, the thermostat itself should be chosen correctly. It must be equipped with a valve with a higher flow resistance from 0.1 to 0.3 bar.
For one-pipe heating schemes, devices are needed in which the valve has a minimum hydraulic resistance and, accordingly, good flow capacity. Danfos suggested using a separate type of RTD-G thermostats in such circuits. They do not change the flow characteristics in the common branch, but affect a specific radiator. Similar devices can also be selected for two-pipe natural circulation systems.
In the case when the heating is installed according to a two-pipe scheme complete with a pump, the valve must be able to control its throughput (for example, for Danfoss it is the N, K and KW series).
Regulator control
By the type of thermostat control, there are three types of devices, and this should also be taken into account if you need to buy a regulator for a specific room:
- With built-in sensors.
They are compact in size and can be used together with radiators, near which air circulates completely freely. Such thermostats work correctly at sufficient distance from the window (22 cm or more), when they are not exposed to drafts. They can also be purchased for installation on radiators located in a separate niche.
- Models with remote sensors.
They are mounted on radiators in those rooms where there is a significant temperature difference between the heating device and in the room itself. Also, these devices are used when it is not possible to install the thermostat horizontally. The sensor is attached to the wall according to the enclosed manual and connected to the bellows through a two-meter capillary tube.
- With a remote control.
Such thermostats are needed where access to the device for setting the temperature is difficult.
Some manufacturers suggest using even more advanced systems that respond to the readings of a sensor located on the street. But such models have a high cost, and there is no need to put them on each radiator separately. It is better to connect an external sensor to the heating boiler - this way it will work more efficiently.
Installation guide
Thermostats are installed on radiators at the very entrance to the heat transfer circuit. When inserting regulators into a ready-made system, the instructions for performing the work will be as follows:
1. Dismantle the radiator by disconnecting it from the supply and return pipes.
2. Drain the coolant (at the same time it is worth rinsing the internal cavities from the accumulated sediment).
3. Screw the regulator shank onto the inlet. This is usually done through a quick-release nut with paired fittings (American) using rubber seals.
4. Install a shut-off valve to completely shut off the water supply to the radiator. In case of an emergency, a failed radiator can be “turned off” immediately.
5. At this stage, it is desirable to place the bypass as well, if it was not included in the circuit earlier.
6. After strapping the heating battery, connect it back to the general system, monitoring the tightness of the connections.
7. At the end of work, a thermal head is put on the thermostat housing with a stem and pressed until it clicks.
8. If you decide to buy a vandal-proof device, you will have to additionally fix the head with a special bolt (you will need a 2 mm imbus wrench).
When the radiator with the thermostat is assembled, you need to close all windows and doors and configure the device. Adjust in accordance with the manufacturer's instructions to ensure correct operation of the thermostat.
The main nuances of the installation
During installation, check the alignment of the arrow on the regulator body with the direction of the flow at a specific point in the heating system. You should also maintain a right angle between the axis of the temperature-sensitive head and the plane of the radiator itself. That is, the automatic bellows device must be mounted in a horizontal position. Manual mechanisms are not covered by this manual - they are placed vertically. After connecting the thermostat to the heating, make sure that its head is not covered by a curtain or any other "screen" that impedes the movement of air in this area. Creating a so-called false climate around the thermostat will cause it to malfunction. If it is impossible to avoid delimitation for some reason, an external sensor will be needed.
While thermostats are indispensable for efficient heating, you shouldn't hang them on every radiator in your heating system you can reach. It is enough to choose the largest appliances in the room, giving at least half of the total heat output, and equip them with thermostats.
Price