Current flows in electrical installations that can pose a danger to humans. For this reason, appropriate safeguards are used to minimize such risks. The most common are overcurrent fuses and residual current circuit breakers. In order for them to perform their function, their parameters must be matched to the heating system.
Overcurrent fuse for heating mat
Current is characterized by two main parameters: voltage and amperage. The first of these is well known. We know that electricity has a voltage of 230 volts at the outlet and is therefore dangerous to humans, while batteries have only 1.5 volts and pose no danger. However, this is not entirely true. This is because an equally important parameter is the current intensity. It tells how much charge flows through the wires. High amperage can cause the cables to melt and ignite, resulting in a fire. Therefore, it is necessary to protect the installation from too much current.
Overcurrent circuit breakers are commonly called fuses. They should be found in every home electrical installation. This is because they provide basic protection against overloading of wires and appliances.
How does an overcurrent circuit breaker work?
When too much current flows through the fuse, the circuit is disconnected. In old models, the fuse link was responsible for this, which melted and needed to be replaced. In circuit breakers, on the other hand, a heating bimetal is responsible for this. When a given temperature is reached, it bends and breaks the circuit. In order for current to flow to the device again, the fuse must be switched to the “on” position.
What kind of overcurrent fuse for a heating mat?
You can find various overcurrent circuit breakers on the market. Single-phase ones have only one lever, while three-phase ones have three levers connected to each other. For heating mats, single-phase circuit breakers are used. You can also find the corresponding marking on each circuit breaker. For floor heating mats, the most common is B 13 A or B 16 A. However, it is worth knowing what this notation means.
- The first letter indicates the speed of the overcurrent circuit breaker. If it is marked with the letter B, the time is 0.2 seconds. This is the amount of time needed for the bimetal to heat up and break the connection. Class C fuses have a higher tripping time and are used with electric motors, which often draw a much higher current during startup.
- The next place in the designation of the circuit breaker is the current rating. In our example, it is a maximum of 13 and 16. This is the average current given in amperes that can flow in the installation without tripping the fuse. This one will turn off only when the current is 2.5 – 3 times higher. Thus, in the case of underfloor heating, it will be 25A.
- Sometimes the letter A appears at the end, in other cases it may not be there. However, in this case it is not any coded information, but only a unit of current intensity.
Choosing a circuit breaker with a rating that is too small will cause it to trip frequently for no reason. On the other hand, a fuse that is too large will simply not work if the heating mat fails.
Security selection table for heating mat
| TOTAL POWER | OVERCURRENT CIRCUIT BREAKER | RESIDUAL CURRENT CIRCUIT BREAKER |
|---|---|---|
| 160 W | B 10 A | 30 mA |
| 240 W | B 10 A | 30 mA |
| 320 W | B 10 A | 30 mA |
| 400 W | B 10 A | 30 mA |
| 480 W | B 10 A | 30 mA |
| 560 W | B 10 A | 30 mA |
| 640 W | B 10 A | 30 mA |
| 720 W | B 10 A | 30 mA |
| 800 W | B 10 A | 30 mA |
| 960 W | B 10 A | 30 mA |
| 1120 W | B 10 A | 30 mA |
| 1280 W | B 10 A | 30 mA |
| 1440 W | B 10 A | 30 mA |
| 1600 W | B 13 A | 30 mA |
| 1760 W | B 13 A | 30 mA |
| 1920 W | B 13 A | 30 mA |
| 2080 W | B 13 A | 30 mA |
| 2240 W | B 16 A | 30 mA |
Residual current circuit breaker for heating mats
Only when the two wires are connected: phase and neutral, current can flow through the electrical system. Sometimes, however, a puncture occurs. In this case, some conductive element comes into contact with the metal part of the appliance housing. This is very dangerous, because such an enclosure is constantly live.
How does a residual current fuse work?
Grounding is extremely important in terms of the operation of ground fault circuit breakers. In this device, two wires are routed – phase and zero. They are located in the electromagnetic loop. As long as the current flowing through the two wires is the same, nothing happens.
However, if part of the current escapes through the ground, an imbalance occurs in the differential current fuse. A pulse is created in the electromagnetic loop, which disconnects the installation from the power supply.
What type of residual current circuit breaker to use in heating mats?
In practice, three types of residual current circuit breakers are used:
- Highly sensitive, responding at current differences of up to 30 mA,
- Medium-sensitive, operating at a current leakage of 30 to 500 mA,
- Low-sensitive, with a current difference of more than 500 mA.
If the heating system is not grounded, the residual current circuit breaker will only trip if the householder is shocked. However, the current flowing through his body must be greater than about 30 mA. At a lower current, the protection will not trip. It also involves the natural leakage of small amounts of current from the grid. More sensitive circuit breakers could constantly disconnect the installation for this reason.
For domestic installations, including with heating mats, 30 mA differential current protection is used.
Heating mat and grounding
Metal components of underfloor heating due to punctures can be live. However, until the current finds an “outlet”, this fact cannot be noticed. They therefore constitute a death trap.
Therefore, grounding is always used in a home installation. This involves the electrical connection of the housing and other metal components to the Earth. Importantly, this is not about a small amount of soil placed in a pot, but the earth outside. Because of its enormous size, it can be assumed that the Earth is the equivalent of a neutral wire.
In practice, when a puncture occurs and the current is on the housing of the device, it flows to earth through the ground and poses no danger to household members.
Use electric floor heating safely
Home installation must be adequately protected. Also electric floor heating, which is most often a separate circuit, has its own overcurrent protection. The residual current circuit breaker is more often installed collectively, for the entire installation. However, it should also have appropriate parameters (30 mA). It is also very important to connect the heating to the ground bus, which should be located in the distribution box.
This is the only way to use the heating mats in complete safety. If you are not sure if you can handle the installation of all components and fuses, get help from a qualified electrician.