How to check a heated floor if it is not working: how to measure the resistance of an electric floor with a multimeter, sensor, how to ring, thermostat malfunctions, checking for a break with a tester

Heating cable is widely used mainly for two things:

in heated floors

for heating water pipes

At one “wonderful” moment, the heated floors stop heating, and the water pipes begin to freeze.

How to find out whether the cable itself is to blame or the reason is elsewhere (automation malfunction, poor contact)?

If you have a Chinese multimeter, and sometimes even without it, you can check this yourself without calling a specialist to your home.

The most important thing is to know where to “poke” the probes and what numbers on the screen will clearly indicate a malfunction or, conversely, the functionality of the cable.

Checking the sensor resistance with a multimeter

If the floor is in good working order, but does not function, then the cause of the malfunction lies elsewhere. There is a method for checking a heated floor sensor with a multimeter, since the device is a resistor, which means it has its own resistance.

True, the multimeter readings largely depend on the floor temperature. At a temperature of 5 degrees, it will show 22 kOhm, and at 40C - only 6 kOhm. In general, the resistance of the heated floor sensor should correspond to the factory setting. When it differs from the declared value by more than 5 kOhm or is equal to zero, then the sensor is broken and should be replaced.

Sensor malfunctions

The sensor works in conjunction with a thermostat and measures the temperature of the heated floor. If the floor heating turns off quickly or severe overheating is observed, then you need to check the sensor.

A visual preliminary inspection of the sensor may reveal the presence of:

burnt contacts;
lack of system power.

You can also determine the voltage level at a certain section of the circuit. The sensor is a resistor with its own resistance. The readings obtained from testing with a multimeter can provide valuable information about the breakdown.

With their help, you can determine which of the sensor elements (relay and capacitor) has failed or the connections are inaccurate.

Diagnostics with the device is carried out after inspection. To do this, you need to turn off the thermostat, remove the panel from the front side, then remove the installation block. Connect both terminals with a voltage of 220 W to the thermostat.

The document for the thermostat indicates the resistance of the device; usually it ranges from 5 kOhm to 120 kOhm, which depends on the body temperature of the sensor. When 5 ⁰C, its value will be about 22 kOhm, and at 40 ⁰C – 6 kOhm.

The multimeter is set to ohmmeter mode. If the indicators coincide with those declared by the manufacturer, then the sensor is working.

Therefore, independent testing of a heated floor is possible using a multimeter.

In a household with heated floors, the owner needs to have a device to check the functionality of the sensor and thermostat with heating cables.

Modern thermostats are equipped with touch screens; they can independently indicate sensor failure.

How to check the functionality of the thermostat?

Let's look at an example of how you can check whether the thermostat is working using an ordinary light bulb.

Step 1. The thermostat is connected to the network in compliance with all rules. That is, the phase wire is connected to terminal L, and the zero wire is connected to terminal N. A temperature sensor and a regular light bulb screwed into the socket are also connected. It will serve as a load indicator.

The light bulb will serve as a load indicator

Step 2. The thermostat connected to the network is turned on using a toggle switch.

Step 3. The lever responsible for increasing the temperature is set to maximum.

The maximum temperature is set

Step 4. If the thermostat is working properly, the light will light up.

Step 5. Using this circuit, you can also check the temperature sensor. To do this, take it in your hand, and the temperature regulator is set to the average value.

Using this circuit you can also check the temperature sensor

Step 6. The temperature control is turned again to higher values. The light will come on again. But when the sensor heats up to the temperature of the human body, it will go out.

The light came on again

Step 7. After this, the system can be left alone. After some time, the light will light up again when the temperature sensor cools down and sends a signal to the thermostat.

The light came on again

Diagnosis of electric floor faults

Failure of heated floors can lead to complete failure of the equipment or a decrease in its efficiency. In the first case, you can start diagnosing immediately. In the second, you first need to objectively evaluate the operation of the system. The fact is that apartment owners often overestimate the ability of electric heated floors to heat a room. As a result, they feel that the system is not working efficiently enough.

If it doesn't heat at full strength

To objectively evaluate the performance of an electric floor, note the time it takes to heat up and compare it with standard values:

The comfort of a film floor without a screed and an adhesive layer begins to be felt after 10 minutes of operation of the system;
Matte floors in the adhesive layer are heated to the temperature set by the thermostat in 6-8 hours;
Cable heated floors under a thick screed warm up for 24 hours.

If your floors fit within the specified standards, then there are no problems. It may seem that the surface is not warm enough due to the difference in body temperature (36.6 °C) and that set on the thermostat (20-30 °C). The task of the electrical system is to heat the floor and air to a temperature that is comfortable for humans, and its average value is only 21 °C.

If the electric floor takes too long to reach operating temperature or cannot reach it at all, then there is at least one of the reasons:

The thermal sensor is installed too close to the heating element. When the set temperature is reached, it causes the thermostat to turn off. But since the heat has not yet reached the floor covering, it remains unheated;
Sensor malfunction. Check the voltage at the heating element terminals and at the power supply without turning off the thermostat. The readings should be the same. Additionally, check the resistance of the sensor, which must match the value specified in the thermostat’s data sheet;
Low voltage. You can check with a multimeter. The voltage is measured at the terminals marked L and N. Before measuring, you need to remove the thermostat from the socket. If the voltage is less than required. Then the problem has been found;
Lack of thermal insulation layer. Heat loss can be so great that your floor will never be able to warm up. Remember, when installing the system you used heat-insulating reflective materials. Were the rules for their use followed? This is especially true for owners of apartments on the ground floor;
Power calculated incorrectly. If the underfloor heating is calculated incorrectly, it will not heat well.

From the list of possible causes of poor floor heating, it is clear that most problems can be avoided at the stage of calculation and installation of the electrical system. Any errors noticed during installation can be more easily corrected before finishing with the finishing coat. And if the screed has already been installed and the tiles have been laid, then repairing the electric heated floor promises to be long and expensive.

If it doesn't heat up at all

If the electric underfloor heating does not heat at all, then you need to carry out diagnostics in the following order:

Check for voltage. The floor stops heating completely only when it is completely absent. If there is power, then proceed to step 2;
Check the sensor by measuring its resistance. If it is faulty, it will have to be replaced. Otherwise, go to step 3;
Check the operation of the temperature controller. Replacing it is the easiest and cheapest way to repair floors. If it is OK, go to step 4
Check the resistance in the circuits using the same multimeter. If it does not correspond to the values indicated in the passport, then you will have to look for short circuits or cable breaks.

If the sensor and temperature controller are working properly, and there is voltage, but the floor still does not heat, then it will need to be repaired. In order not to dismantle the entire coating, you need a special tool for troubleshooting. This is especially true if the mat or cable is mounted in a screed, the installation of which is a labor-intensive and expensive task.

Determine the side with a cliff

Using an ohmmeter, determine which side (towards the thermostat or towards the end of the mat) the break is relative to your cut. Twist the black and white wires together on the thermostat using a jumper clamp (do not connect the ground wire). Check the resistance from the cut to the thermostat. The readings should appear (a fraction of the factory value, since not the entire cable is measured), and there should be no ground fault. If this is not the case, then the tear is on that side and the OTDR should be reused as described above to determine the distance of the tear from the cut site. If the original drawing and estimate were done correctly, you should be quite close and the distance reading in meters should be small.

If everything is fine with this chain, go to the other side of the cut and use an ohmmeter to measure towards the end of the mat. If the readings obtained do not correspond to the complete circuit, reuse the OTDR as described above to get closer to the break location.

Checking when a fault occurs

During the operation of the heated floor, deviations from the normal operating mode may occur. Let us consider the main manifestations of system dysfunction.

No heating over the entire floor area

In this case, you need to start checking for a break from the “head”, that is, make sure that power is supplied to the system. If the mains voltage indicator does not light up, you need to check the machine on the panel. After this, you can check whether voltage is supplied to the input of the temperature controller. The presence of voltage at the input and its absence at the output indicates a malfunction in the thermostat itself. The reason may be either in the regulator itself, or in the temperature sensor, which can be checked by measuring its resistance. If you apply voltage to the heated floor directly, without a thermostat, you can test the cable for serviceability.

A situation may arise when the circuit breaker in the panel that supplies the heated floor is turned off by the protection. This indicates a short circuit. To localize the short circuit, we check the resistance between the phase and neutral wires supplying the heated floor. Before ringing the cable, remove the voltage. Disconnect the power wires from the temperature controller. We measure the “phase-zero” resistance in the area from the panel to the thermostat. If the device shows zero resistance, the wiring in this area is damaged; if the resistance is high, we continue the search. Disconnect the underfloor heating cable from the temperature regulator. We take measurements at the regulator input. If a short circuit is detected during the test, then the damage is located inside the thermostat. If not, all that remains is the underfloor heating cable itself. You can check this by measuring the resistance between the cable cores. In this case, you cannot do without opening the floor surface.

What to do when voltage is supplied to the heating elements, but heating does not occur? In this case, the cable must be tested, that is, checked for integrity (or for break, if you like). Having set the multimeter to resistance measurement mode, we take measurements between the cable cores. A resistance value close to infinity indicates a conductor break.

The video below clearly shows how to check an electric heated floor with a multimeter by measuring the resistance of the heating cable:

The heating temperature of the heated floor is not adjustable

If the heating elements over the entire floor area warm up, but the temperature does not change when the setpoint set by the regulator is changed, it is necessary to check the system, determining one of two possible options:

malfunction in the temperature regulator circuits;
The temperature sensor is faulty.

In this case, the temperature regulator must be dismantled, disconnecting all wires from it and sent for repair. How to check the temperature controller for a heated floor is shown in the video:

If you suspect a sensor, you should check its resistance. To do this, the sensor wires are disconnected from the regulator and the resistance between them is measured. A conclusion about the serviceability of the heated floor temperature sensor can be made by checking the value of its electrical resistance and comparing it with the passport data. As a last resort, you can do without a multimeter. Since this element cannot be repaired anyway, you can proceed as follows. Buy a known-good sensor, place it on the heated floor, and connect it to the regulator. If you ensure good contact of the sensor with the floor, the system should work if the regulator is working. After this, you can install the new sensor in place. This will require opening up the floor surface.

Resistance measurement

Before starting work related to pouring the screed during the creation of the system, experts recommend performing the following procedure: measuring the resistance of the heated floor with a multimeter, or rather the heating cable:

Complete the installation of the heated floor and prepare for further work.
The resistance value is found in the passport or on the tag attached to the cable. In this case it is 150.9 ohms. It is permissible to change it by 5 - 10% upward or downward.
The multimeter is turned on in measurement mode.
The probes of the device are placed on the wires that extend from the heating system.
After measuring the resistance of the heated floor, the indicator will be visible on the multimeter. It must be equal to the value specified in the cable passport.

Where do leaks come from in the heating system?

The most common cause of leaks in metal pipes is corrosion. Steel, even treated with special coatings, rusts. Only the speed of the process differs. It depends on the operating conditions of each specific system.

Heating pipe rupture

Metal is affected by temperature changes, moisture, and water hammer. Impurities in the coolant may contain aggressive chemicals and abrasives that accelerate corrosion. The places where system elements rust most quickly begin to leak. As a rule, these are connections, joints, seams.

Polymer materials do not rust, but this does not mean that they do not leak. Sooner or later, metal-plastic pipes may leak. Most often this happens if they are chosen incorrectly. Some home owners save money and buy cold water pipes. This is a big mistake, because... leads to deformations and breakthroughs in the system.

Homeowners who choose low-quality products for heating often suffer. Cheap polymer pipes swell, burst, and leak. If this happens, you have to replace the damaged sections. Imaginary savings result in additional costs of money, effort and nerves.

Metal-plastic pipes, which are specially designed for heating systems, are least at risk of leaks. They are designed to withstand high coolant temperatures, do not deform and can last for several decades.

Metal-plastic pipe repair

Functionality check upon purchase and after installation

The first check is carried out when purchasing the system. You need to ask the seller to demonstrate the operation of the device. If the attached documentation indicates the resistance values of the mats, it is advisable to check their actual values with a multimeter or tester. You can also check the insulation resistance. This can be done using a multimeter in high resistance mode, or a megohmmeter.

After installing the heating elements, before laying the tiles and before pouring the screed, you need to connect the electric heated floor to the power supply and observe its operation for a while in different modes. You should make sure that the thermostat, temperature sensor are working properly and that the heating cable is intact. With a working system, all sections of the cable should be heated evenly, the temperature of the heating elements should change in accordance with the setting of the thermostat.

If there is such a possibility, it is most convenient to check the uniformity of heating of the elements with a thermal imager, on the screen of which you can see whether each section of the floor is working or not. This device produces an image that is created by infrared rays, as shown in the photo below:

At this stage, if any malfunction is detected during testing, it is better not to look for the cause and not try to eliminate it. You need to take advantage of the warranty and replace the system.

First stage of checks

At the beginning of each of my consultations, I always immediately ask the client if everything was in order with the materials when they were purchased. And more than once I hear that equipment was purchased from an online store, and therefore I had to rely on the integrity of the seller.

Since many people are trying to save money, buying online is often justified. But you should always remember that a very cheap product is a clear sign that they are selling you a fake. But in any case, equipment of any complexity should always be checked. And the easiest way to do this is when it is bought in a specialized store.

The seller is always obliged to demonstrate the functionality of the device upon request. He must measure the resistance of the heated floor (the mats and insulation themselves) with a multimeter and compare the data in front of the buyer with the attached documentation. This is necessary to see the difference between real indicators and those indicated by the manufacturer.

Source sto-auto.by

If the goods are sent by the online store by mail, then upon receipt of the parcel the client has the right to inspect the contents. It is necessary not only to check the appearance of the product for damage, but also to test it, for example, with a megohmmeter. And if such a task is impossible to complete on your own, then ask an electrician you know to accompany you to the post office.

How to check the temperature sensor

Checking the temperature sensor is also not difficult when repairing an electric heated floor. To do this, you again need to test the device yourself with a multimeter to make sure that the nominal and actual resistance corresponds. If the temperature sensor breaks, it must be replaced with a new one. If you followed the recommendations for laying heated floors under the tiles and placed the temperature sensor in the corrugation, it will not be difficult to remove it from under the screed. Otherwise, if the sensor gets stuck under the floor, it is better not to touch it, but to solve the problem in a simpler way - by installing an air temperature sensor. This device will give a signal to turn the thermostat on/off based on the temperature in the room, and not under the screed, as was previously the case.

You can also avoid repairs by purchasing a thermostat with a timer, which will turn the system on/off according to a set point. In addition, there are IR temperature sensors that analyze the heating of an electric heated floor using infrared radiation.

How to ring a warm electric floor

Before ringing the heated floor with a multimeter, it is set to the sound signal icon located next to the ohmmeter scale. When the probes touch each other, a sound is heard, indicating that the circuit is closed. If you simultaneously touch the conductors of the heated floor with the probes, a buzzer should appear.

When it is missing or interrupted, this indicates a tear in the vein. After you have managed to figure out how to ring a warm floor, you need to do a similar procedure with a temperature sensor. If the sensor resistance is missing or does not match the specifications, it is clear that it is faulty.

How to check a heated floor with a multimeter?
The photo and video below show a step-by-step check of a heated floor.
We will also tell you how to ring an electric heated floor without a multimeter.

When purchasing electric heated floors (heated floors under tiles, heated floors in a screed), remember that the floor (heating cable, heating mat or thin heating cable) is connected to the network only after installation and the screed or tile adhesive has completely dried.

Infrared heated floors can be turned on immediately after installation.

It should be noted that complete hardening and drying of the cement-sand screed occurs within four weeks.

It is necessary to check the serviceability of purchased products at several stages.

Detecting a heated floor malfunction using an example

Since a heated floor must be connected through a thermostat with a remote temperature sensor, we will consider the connection diagram using the example of a thermostat for a heated floor RTC 85.26.

We disconnect the voltage supplied to the thermostat from the network.
We gain access to the rear panel of the thermostat.

We already know that the heating cable (cable floor) or heating film (infrared film floor) is a load and is connected to contacts No. 3 (N-zero) and No. 4 (L-phase load). – we measure the resistance, it must correspond to that stated in the passport *.

* If you have lost your passport, then you can calculate the resistance value using the formula R=U/P, knowing the voltage value is 220 Volts and the power, for example it is 1.2 kW, we find the resistance R=U*U/P=220*220/1200 =40.3 Ohm.

If you do not know the power of a heated floor, you can calculate its approximate value. Room area (m2) multiplied by 150W/m2).

For example: toilet room 6 m2 *150 W/m2 =900 W. Hence the resistance is 220/900 = 53.7 Ohms

In the case of using infrared film heated floors, you can check the resistance of each individual heating element. To do this, disconnect the wires (see connection diagram) and take resistance measurements. Compare the readings with the calculated values.

Note

if the instrument reading is zero, this means that a short circuit has occurred in the system, more often it is a short circuit of the wires due to overheating (the cross-section is incorrectly calculated).
if the instrument reading is infinity, then this means that a break (burnout) of the heating element has occurred in the system, most often in the coupling.

If the resistance measurements correspond to the data specified in the passport, then you can breathe a sigh of relief - the heating elements of the heated floor are in good working order!

This means the reason is in the thermostat, you will agree that checking and replacing it is much easier and cheaper, but this is discussed in a separate article, checking the functionality of the thermostat.

** heated floor, no matter what it is, cable, film, Chinese or according to the passport “made in Denmark”, but in fact in China - is a load

The second way to check the performance of a heated floor

If you are far from electricians (i.e. you are strong in the field of philology or other sciences no less valuable to humanity) and did not understand anything from what you read, then you can check the serviceability of heated floors in a simple old-fashioned way: checking the functionality of a heated floor by connecting a heating element directly to the 220V voltage, bypassing the thermostat.

Turn off the electricity (turn off the machine on the distribution panel)
We connect the electric wire coming to contact No. 1 with the wire connected to contact No. 3, and the electric wire coming to contact No. 2 with the wire connected to contact No. 4. This means that we connected the heated floor directly to the panel, bypassing the thermostat.

We turn on the machine on the control panel for 30-40 minutes and wait for the floor to heat up. If the floor becomes warm, that's good. The heated floor works. This means the thermostat is faulty, but if even when connecting the heated floor directly, bypassing the thermostat, it does not heat up, then you need to look for the place where the wire burned out.

Attention. If you connected the heated floor directly and when you turn on the electricity, the machine knocks out, then there may be a short circuit or a malfunction of the machine, check the resistance of the heated floor, it should not go to zero

Did you manage? FINE! you can go and receive a reward from your beloved.

If you can’t cope and have questions, it’s also not a problem, look at the QUESTION-ANSWER section or call the numbers listed on the website, we’ll figure it out together.

How cozy and comfortable a home is depends largely on the temperature and the air in the room. But with centralized heating, it is impossible to control the temperature yourself, so many, for the sake of their own comfort, especially in the off-season, try to purchase additional autonomous heat sources. In this market, underfloor heating systems currently hold a leading position due to their undeniable advantages: affordable prices, quick and easy installation, the ability to control and maintain the temperature down to a degree, etc.

However, like any heating device, the underfloor heating system can fail. Such cases are rare, but cause trouble for the owner. One of the most common malfunctions in the operation of a heated floor is a burnt-out thermostat. We will tell you how to check the thermostat on a heated floor in this article.

Types of heating cable

Let's start with the fact that there are two types of heating cables:

resistive (with constant resistance)

Most often they are used in heated floors.

self-regulating (more suitable for heating water pipes and roof snow melting systems)

Their power “floats” depending on temperature. This is due to a change in the resistance of the semiconductor matrix, between which two cores are placed.

The method of checking both of them is basically the same, but the readings that will be displayed on the multimeter screen can differ significantly and mislead many.

Resistive heating cables generally have two working cores and a protective braid. However, single-core specimens are also found.

They have one working core, and the end of the cable, after laying it on the floor, has to be brought to the beginning of the loop so that it can be fully supplied with phase and zero. For such varieties, all measurements are taken between the beginning and end of the loop.

Design and arrangement of electrical cables

A heated floor system, mounted from an electric cable or using infrared film, consists of a number of elements:

heating cable, which is a source of thermal energy;
a temperature sensor that records the degree of heating of the wires;
a thermostat responsible for connecting all the component elements into a common structure and regulating the switching on/off of the floor in accordance with the heating temperature of the cable.

The thermostat or thermostat looks like a small switch. It is intended to adjust the voltage that is supplied to the wires. Connect this device to a standard electrical network using phase and neutral wires.

The thermostat regulates the voltage automatically. It is supplied directly to the heating cable after the floor in the room has cooled. The degree of its heating is monitored by a temperature sensor, which is mounted near the wires and filled with cement mixture.

Residents independently set the temperature at which the floor surface heating system should turn on. The cable used to equip such a heating structure can be resistive and self-regulating. The latter of them independently reacts to temperature fluctuations and changes the resistance level. In turn, a resistive cable does not have such functions.

When arranging the system, either a single two-core cable or two single-core cables are used, which are arranged in parallel. The first of them is a mesh of wires with a plug on one side. It is unacceptable to cut it and lay it in a screed in places where large pieces of furniture or equipment will be located.

In turn, single-core cables can be cut and nothing bad happens to the insulation. In the same way, infrared floors are trimmed in accordance with the area of the room that requires heating.

Methods for checking the functionality of a thermostat for a heated floor

You can check the serviceability of the thermostat by replacing it with another known-good thermostat. If there is no second thermostat, then you can connect the heated floors “directly” to the 220 V network, bypassing the thermostat and make sure that the “warm floor” is working.

turn off the voltage;
to the wire connected to pin 1 (L-phase) we connect wire 4 (L-phase to the load);
to the wire connected to pin 2 (N-zero) we connect wire 3 (N-zero load);
Apply voltage and wait for some time, for example 1 hour. If the floor becomes warm, there is a problem with the thermostat.

We de-energize the system and replace the faulty thermostat with a working one.

I’m glad if you were able to figure it out on your own, but if you still have questions, then call the numbers listed on the website and we’ll figure it out together.

Heated floor repair

Warm floor doesn't work! What to do?

A typical customer case! You have decided to install a heated floor in your home, and the builders who are doing the renovations say, “They have been laying floors since early childhood. More than 1000 heated floors have already been installed and everyone is happy. What should I put there?” You, as a person who sincerely trusts your builders, are afraid to show doubts about their professionalism and entrust them with the work of installing heated floors. From this moment the headache begins! The builders finished the repairs and left for their homeland. The old tiles have been laid, the cold weather has set in, but the warm floor is not working! Let's start looking for the cause of the problem.

1. Floor temperature sensor. Each thermostat comes with a floor temperature sensor, which is installed in a corrugated tube and mounted in the wall and floor in a certain way, under a certain bend. So that it can be replaced in the future. In a floor heating system, the floor temperature sensor is a “consumable item”. Sooner or later it will need to be replaced. This sensor can work for you for 10-15 years, but it can fail after 3-5 months

That's why it's very important to install it CORRECTLY to avoid further problems.

Bricked sensor

How to check the serviceability of the heated floor sensor?

To check the serviceability of the floor temperature sensor, you need to remove the front panel. Unscrew the thermostat installation block and check the resistance of the floor temperature sensor with a multimeter. Each sensor has a factory resistance statement. Your sensor value should match it. If the resistance differs by more than 5 kOhm, or is early 0, then the sensor is faulty and requires replacement.

2. Thermostat. More often, either the relay or the capacitor fails. You can check the functionality of the thermostat by switching to heating mode by applying power to the terminals of the heated floor. The average cost of repairs is about 3,000 rubles. In many cases, it is more advisable to purchase a new thermostat from the same manufacturer. Since the thermostat must be from the same company as the sensor installed in the floor. (However, the DeviTouch thermostat works with floor temperature sensors from manufacturers Teplolux, Eberle, Ensto, Fenix, Oj Electronics, Raychem, etc.)

3. Heating cable (mat). In 95% of cases, the cable heating system fails due to unqualified installation. The most vulnerable part of the heating cable is the coupling. During installation, it is necessary to observe all the rules for laying pitch, cable bending, and the location of the coupling. Also, when purchasing equipment, you need to understand that the cable will be under the tiles. You install heated floors for at least 10-15 years. There is no need to chase cheapness, since a cheap cable is not reliable and may soon fail.

How to check the serviceability of the heating cable?

Each cable has its own resistance. It is necessary to check the resistance value 3 times. Before installation. After installing the heated floor. After filling with screed or tile adhesive. If the cable resistance differs significantly from the rated values, or is equal to zero. This means the cable may have failed. In this case, it is necessary to check the cable with a megger to check the insulation resistance of the heating cores and the shielding braid.

Repair of electric heated floor.

Equipment for searching for cliffs.

Repairing a heating cable (mat) begins with searching for a broken cable or a damaged coupling.

Then the tile in this place is opened and a repair coupling is installed. After this, the resistance is checked and

checking with a megger, as well as a test connection.

In conclusion, I would like to say: Each heating system, including warm floors, must be calculated and selected according to the heat loss conditions of your room. Despite its apparent simplicity, there are many nuances that must be taken into account when choosing a heated floor and thermostat and further installation.

We offer a service for on-site diagnostics of heated floors. Diagnostics will include checking the functionality of your thermostat, floor temperature sensor, and heating cable (mat). Cost: 2000 rubles.

What in the end...

Most elements of a heated floor are forever hidden under a decorative coating. To be sure of the long-term operation of the equipment, it is necessary to conduct preliminary testing upon purchase and immediately after installation. And in case of complete or partial failure, have a multimeter on hand. With its help, you can always ring the system and identify the area with a short circuit.

Question

Write in the comments what you think - is it worth using heated floors as the main source of heating at home? Usually it is used in the form of additional insulation of individual rooms. Indeed, in the event of a system failure, dismantling the coating and repairing it will cost a pretty penny...

Checking when a fault occurs

During the operation of the heated floor, deviations from the normal operating mode may occur. Let us consider the main manifestations of system dysfunction.

No heating over the entire floor area

The video below clearly shows how to check an electric heated floor with a multimeter by measuring the resistance of the heating cable:

https://youtube.com/watch?v=f9lTMSrwI-4

The heating temperature of the heated floor is not adjustable

malfunction in the temperature regulator circuits;
The temperature sensor is faulty.

In this case, the temperature regulator must be dismantled, disconnecting all wires from it and sent for repair. How to check the temperature controller for a heated floor is shown in the video:

How to identify problems

The thermostat has an electronic display that shows the voltage; to check how it works, you need to:

dismantle the device;
use a multimeter to measure the voltage, setting the maximum floor temperature - the sensors should show 220 V;
then the relay knob needs to be turned in the opposite direction - set the minimum temperature - the sensors should show no voltage.

Measuring the resistance of electric underfloor heating cables

Thus, you can check whether the relay and the thermostat itself are working.

To determine the health of the heating cable, it is necessary to measure its resistance. This is done using a multimeter as follows:

Calculation of laying heated floors

the resistance value must be divided by the voltage - 220 V - you get the amount of current that passes through the system;
the current value must be multiplied by the voltage (220V) - the power of the electric floor is obtained, which should not deviate from that declared by the manufacturer (specified in the system passport) by 5%.

If there are deviations, they indicate a malfunction of the heating elements.

Basic working elements of a heated floor

To identify the cause of a heated floor malfunction, you need to know the main components of the system that can affect its operation. So, in general, an electric heated floor system consists of:

thermostat,
temperature sensor,
and directly the heating element itself, which can be a heating cable, a heating mat (a cable fixed on a grid with a certain pitch), or an infrared film.

The functioning of the floor occurs as follows: a current passes through the heating element, after which heat is emitted. Temperature data is sensed by a special sensor, transmitting the received readings to the thermostat.

The job of the thermostat is to control and maintain the temperature: the desired temperature is set manually, and the thermostat activates/deactivates the heated floor system to establish the desired temperature. In order to check the serviceability of each of the elements of the overall underfloor heating system, there are a number of actions.

The first step is to determine the performance of the heated floor

The operation of a heated floor may be disrupted due to a malfunction in the heating element itself. To check its operation, you need to connect the floor to the network without a thermostat. After connecting, you need to wait a while and check whether all areas of the heated floor are heated. If the floor heats up evenly and no malfunctions are detected, it means that the floor heating thermostat or its sensor is not working.

Note! When the underfloor heating system operates from the network without a thermostat, heating is carried out at full power, and this significantly increases energy consumption, while heating must be kept under constant control - turn it on/off manually

How to check the thermostat of a heated floor?

Checking the underfloor heating thermostat involves carrying out a series of simple sequential steps that will help identify the cause of the problem.

First, check if all the wires are located correctly. To do this, focus on their placement diagram.

Secondly, we check the voltage on the contacts. Set the thermostat to the minimum temperature setting, apply a voltage of 220V to the device, and use a special device (multimeter) to check the voltage values on contact No. 1 and contact No. 2. The voltage at these contacts should be the same as at the input, that is, 220V.

Thirdly, we check the serviceability of the relay and temperature sensor.
We move the toggle switch to the “on” position, set the regulator to the maximum temperature value, and apply voltage (220V) to contacts No. 3 and No. 4. When carrying out all these actions, listen carefully: if clicks are constantly heard at this time, then the thermostat for the heated floor has broken down. But if there is no voltage on these contacts, then this indicates a breakdown of the temperature sensor. If you have a programmable thermostat, then information about sensor failure will be displayed on the display automatically. Date: September 25, 2022

How can I replace the temperature sensor?

The temperature sensor used in thermostats for heated floors is a thermistor with a negative TCR (temperature coefficient of electrical resistance). This means that when heated, the resistance of the sensor decreases.

The second parameter required to select a temperature sensor is the resistance value under normal conditions, at 20°. The resistor value is usually indicated on the thermostat body next to the temperature sensor connection terminals or in the product data sheet.

To select a temperature sensor, this data is quite sufficient. The only thing that is difficult to find out and select is the TKS characteristic, that is, the change in the resistance value of the temperature sensor due to changes in ambient temperature.

But this is not a critical parameter; anyway, the temperature on the thermostat is set experimentally. After all, the temperature sensor is installed in the floor and the set temperature on the thermostat sets the floor heating temperature, and not the room temperature.

How to determine the resistance of a temperature sensor

The temperature sensor of the SPYHEAT ETL-308B thermostat has failed. Its technical characteristics were unknown. They had to be determined experimentally.

To do this, external circuits were connected to the thermostat, in accordance with the diagram printed on its body - supply voltage was applied, an incandescent light bulb was connected instead of heating elements, and a variable resistance was connected instead of a temperature sensor.

I had a resistance magazine available, so I decided to use it for calibration. The resistance magazine is a box in which high-precision resistances are placed and there are switches with which you can set the desired value.

Consistently setting the regulator knob to positions from 20° to 30° and changing the resistance value with the knobs in the resistance magazine until the thermostat operates, I built a sign.

Dependence of the thermostat response on the resistance value of the temperature sensor

Temperature set on the thermostat, °C	Turn-on resistance, kOhm	Turn-off resistance, kOhm
20	16	14
25	10	12
30	8	9
35	6	7

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Based on the data in the table, for this heated floor thermostat, a thermistor with a negative TCR of 10 kOhm is suitable as a temperature sensor. The resistance value of the resistor when turning the light bulb on and off turned out to be different due to hysteresis in the thermostat itself. This is necessary so that the heating element of the warm floor turns on less often.

Determining the temperature sensor rating can also be done using a 47 kOhm variable resistor. You just have to disconnect the thermostat from the network every time after turning the light bulb on and off and measure the resistor resistance with a multimeter.

You can do without measurements. It is enough to have several constant resistors with values ranging from 10, 15, 20 and 30 kOhm. Resistors are connected in turn instead of the temperature sensor. By rotating the thermostat knob, you need to determine which resistor the light bulb will turn off and on at a temperature of about 20°C.

Thermistor selection

You could buy it ready-made, but to do this you had to place an order online and wait for delivery. In addition, the price of the issue reached 20% of the cost of the thermostat itself.

Therefore, it was decided to make a temperature sensor from available thermistors. There was a thermistor with a nominal value of 10 kOhm with a negative negative TKS type MMT-4. I decided to use it for repairs.

For connection there was a piece of wire with which the failed temperature sensor was connected. In principle, any wire can be used to connect the sensor, as long as it can withstand a temperature of at least 100°C. To check, the ends of the wires were stripped and wound onto the thermal resistance terminals.

Next, the thermistor was located in close proximity to the incandescent light bulb connected to the terminals for connecting the heating element of the heated floor. Supply voltage was applied to the thermostat.

After a few minutes, the light bulb heated the thermistor, its resistance decreased, and the thermostat turned off the voltage supply to the light bulb. When the thermistor cooled down, the light came on again, and this continued ad infinitum with a period of several minutes.

After checking the operation of the heated floor thermostat, wires were soldered to the MMT-4 thermistor with soft solder and pieces of insulating tube were put on the soldering points.

For reliability, you can put a heat-shrinkable insulating tube on the thermistor. A homemade temperature sensor was installed during the installation of a heated floor and showed stable operation.

As you can see, even without experience in repairing electrical appliances, you can repair a thermostat for a heated floor with your own hands at home, including making a temperature sensor from a standard thermistor.

Attention, the electrical circuits of thermostats are galvanically connected to the phase of the electrical network. Touching exposed parts of a circuit connected to an electrical outlet may result in electric shock.