Electric and water floor heating systems are unable to independently maintain the set temperature in the premises of a private house. The owner adapts to manually adjust the power of the boiler or heating circuits, achieving a comfortable air temperature. To organize automatic climate control, you need thermostats for underfloor heating (TP) installed in each room. The purpose of the publication is to describe the existing types of thermostats, installation methods and wiring diagrams of control devices.
How the thermostat works
The remote thermostat for underfloor heating is a circuit breaker that breaks or closes the electric circuit after reaching the temperature set by the user. As a result, heating stops or resumes. According to the principle of operation, the floor heating regulators are divided into 2 types:
- Mechanical with a temperature sensor in the form of a bimetallic plate. From heating, this element bends and at a certain moment breaks the chain. Then the plate cools, straightens and closes the contacts again.
- In electronic (relay) controllers, the temperature sensor is a thermistor that changes the resistance to electric current depending on heating. The controller chip captures this change and issues a relay command, the winding opens the contacts, the circuit breaks.
Reference. Electronic devices are equipped with their own source (batteries) or connected to a house network. The simplest mechanical thermostats operate without external power. This is not an advantage, because water management still requires electricity.
Now let’s explain how automatic thermostat control is implemented using room thermostats. Electric heating circuits (cable sections, infrared film) work as follows:
- The thermostat installed in the room is connected to the gap of the main power supply line. While the room is cold, the circuit is closed.
- The homeowner sets the desired temperature on the appliance, and the heating is turned on. When it reaches the required value, the temperature sensor is triggered, the circuit opens, the power line is de-energized.
- After cooling by 0.5–1 degrees, the power supply resumes, heating continues. By the way, the difference between on / off temperatures is called hysteresis.
The principle of operation of the thermostat for a water floor heating is the same. Only the relay opens the power circuit of the thermoelectric drive (otherwise - the servo). He stands on the distribution manifold TP and closes / opens the flow of coolant into the heating circuit.
Thermostats for electric and water TP - what is the difference
In fact, there is no difference, in both cases the thermostat performs one function - it turns on or off the heating, interrupting the supply of voltage to the actuator - a heating cable or servo drive. But not every device is suitable for working with electric floors, for example, a purely mechanical device cannot be used. Let’s explain why:
- The heating of the electrical TP is controlled by a remote sensor located in the floor between the loops of the resistive cable. It allows you to limit the maximum temperature of the flooring, protect the cable section from overheating.
- In mechanical temperature controllers there is a plate that responds to changes in air temperature. The device is not designed to connect an external temperature sensor, so it "does not see" the degree of heating of the floor screed.
- Film underfloor heating works in a similar way.When it is necessary to regulate the temperature of the air, a relay thermostat is selected, equipped with an internal sensor and terminals for connecting an external one.
Note. The temperature controller simultaneously processes the signals of the floor and integrated sensors. When 1 out of 2 thermistors shows that the set temperature threshold has been reached, the electrical heating switches off.
To adjust the water heating circuits, an air sensor of the heated floor is used, a remote meter is installed as desired or if necessary. For example, to control edge zones that are very cooled. The temperature of the coolant is limited by control valves on the manifold - RTL thermal heads or a mixing valve with an overhead / immersion sensor.
4 types of underfloor heating regulators
By functionality, thermostats can be divided into 4 varieties:
- mechanical, working at air temperature;
- relay with a minimum set of functions and a built-in air sensor;
- electronic devices for 2 temperature sensors with a display and the possibility of programming;
- same with wifi remote control module.
Addition. By the method of connection, thermostats are divided into wired and wireless. In the first case, the device is connected to the power supply circuit directly, in the second - through a special relay unit with a receiver - receiver of radio signals.
Any of the listed thermostats can have 2 or 3 switching contacts. What is the difference:
- The 2-pin controller "can" only break the circuit (turn off the power) when the temperature threshold is reached.
- A universal 3-pin device simultaneously closes the first line and opens the second.
The last paragraph requires clarification. If the temperature controller controls a servo drive of type NO (normally open), then to shut off the coolant, on the contrary, you must apply voltage, and not turn it off. So, with sufficient heating of the room, the circuit should be closed, the wires are connected to the terminals No. 2 and No. 3 of the thermostat.
The NC thermoelectric drive for a water floor is normally closed when there is no voltage. To stop the flow of coolant into the circuit, the regulator must de-energize the servo drive. Then the cable joins the contacts No. 1 and No. 3, as shown in the diagram.
The simplest mechanical thermostat is only able to maintain the room temperature at one set level, working in tandem with the servo drive NC of a warm water floor. More advanced electronic controllers have many additional features:
- the ability to connect 2 temperature sensors;
- 3 switching contacts;
- frost protection mode - switching on heating in case of cooling the house to + 3 ... 5 ° C;
- regulation of the hysteresis value;
- touch control display showing time, date and controlled temperature;
- the thermostat is programmed for a day / week in advance, the number of events per day - 6 or more;
- fault indication, self-diagnosis, self-training;
- built-in wi-fi module for controlling the thermostat through the smartphone application.
The first 3 functions are available in almost all relay thermostats. If you want to get more, you have to buy a digital model of the device.
Reference. The price of a Danfoss brand BasicPlus electronic thermostat is 20 euros. A similar device with an LCD display will cost 40 €, a programmable modification WT-P costs 54 €. Chinese counterparts are 2-3 times cheaper.
Instrument Selection Tips
We believe that installing mechanical thermostats on warm floors is pointless. These devices are somewhat outdated, the number of functions is limited, the accuracy of the temperature maintained is poor. Devices can be used in utility or technical rooms where it is necessary to maintain + 15 ... 18 ° C around the clock.
The type of microprocessor thermostat is selected depending on the heating method, operating conditions and personal wishes:
- It is better to take the regulator for the electric floor together with the heating cable (film) and sensors from one manufacturer. For example, Devi, Caleo, and Teplolux sell their own control devices.
- If you have to buy a thermostat for electrical transformers separately, you should choose any two-contact device equipped with terminals for connecting an external sensor. Pay attention to the indicator of maximum power that the regulator is capable of switching (usually lies within 2 ... 4 kW).
- Under water heated floors, it is better to take a universal (3-pin) temperature controller, an external temperature sensor - if necessary. Switched power does not play a role, since servos consume 1 ... 3 W of electricity.
- The number of additional “bells and whistles” depends on your needs and wallet. But if you need real energy savings, consider programmable models that include heating on schedule. During working hours or at night, the temperature in the house can be lowered to 18 ... 20 ° C.
Installation of temperature controllers is provided in each room. So, you have to pull the wires from there to the comb of the TP, where the servo drives of the water circuits are located. Such "electrification" is inappropriate in apartments with a fresh designer renovation. Solution: Install a switching unit with a receiver near the collector, and wireless battery thermostats in the rooms.
Reference. Typically, the switch blocks have 1-2 relay outputs for connecting a circulation pump or a boiler burner. Danfoss switching device costs about 100 euros, TP5001A-RF wireless regulator - 82 €, RX type receiver for 3 thermostats - 95 €.
Installation and connection of a temperature regulator
Before installation, carefully read the operating instructions for the device. Usually it contains the following installation instructions:
- height of the thermostat above floor level - 1.5 ... 1.7 m;
- Do not place the regulator with an air sensor near sources of heat or cold - heating radiators, air conditioners, ventilation openings;
- technological distance from window and doorways - 1 m (minimum);
- observe the maximum distance between the thermostat and the distribution manifold of water-based TP (the cable length is indicated in the instructions);
- an external sensor is located exactly in the middle between the floor heating loops at a distance of 500 mm from the wall;
- the floor temperature sensor is mounted inside the corrugated pipe, it should be easily stretched after pouring the screed.
Overhead devices are screwed directly to the wall, the wiring is laid in the gates. Under the built-in thermostats, a recess is made, an ordinary socket is placed.
Tip. To connect the regulator, use a twin-core copper cable with a cross section of 0.75 mm². The circuit diagram for connecting an electric underfloor heating circuit with an external sensor looks like this:
If the cable heating section consumes more power than the thermostat can switch, you need to use a modular contactor in the circuit. The specified actuator is mounted on a standard DIN rail.
Some versions of thermostats have a contact for connecting a timer. This solution allows you to reduce the temperature in the room by 5 degrees once a day without acquiring an expensive digital model of the device. The timer circuit is shown below.
We turn to the warm water floors. The simplest way is to connect the thermostat to the servo drive directly (in series). Only first find out the type of drive, “normally open” must be docked with the make contact of the device, “normally closed” with disconnect. Often manufacturers put on the terminals the corresponding markings - NO or NC. COM contact is shared.
To implement multi-zone floor heating of a private house with wireless temperature controllers, use the following circuit diagram. Terminal numbers and other details are not indicated here, as equipment from different manufacturers is marked.
Reference. Patch panels, receiver receivers and wi-fi modules are produced by many well-known manufacturers - Legrand, Danfoss and others. How the thermostat-switchgear bundle functions is described in the video.
Finally, about setting the temperature
To configure each thermostat for a warm floor and check the operability of the system as a whole, you must turn on the heating and set the desired temperature on all devices. Please note that the house needs to be fully heated. The optimal mode of operation of the boiler is 60 ° C, if the heat generator starts to “cycle” (often turn off and start), it is better to reduce power.
The essence of the setting is to select a comfortable temperature in all residential premises. The thermostat display does not always correspond to our feelings, so the settings will have to be adjusted during operation. A separate issue is the programming of heating according to a schedule, this procedure is described in the instructions for a specific device.