Electrical installation for underfloor heating

Every house should have a design for the electrical system, including electric floor heating, which includes heating mats and heating cables. Here are tips on how to do it if such a project is not available for some reason. The only requirement is to know the power of the heating circuits installed in each room. Read our tips on how to prepare the electrical installation for the heating mat and floor cable.

Electric floor heating installation project

1. Each room equipped with a heating mat or floor heating cable must be controlled by a room thermostat.
2. Heating mats and heating cables with fixed resistance, according to the regulations, must be controlled by a thermostat that regulates the temperature using an external floor temperature sensor. How to install a temperature sensor in a heating mat?
3. Since most thermostats have an air temperature sensor in the housing, it must necessarily be located in the same room. Indoor or outdoor thermostat?
4. It is recommended that each thermostat have a separate fuse protection, including overcurrent and residual current protection, which involves pulling a separate wire with electrical power to the point of the power box. What fuse for the heating mat?

Why install a separate power cord and fuse?

1. Safety.
2. Proper protection of the heating circuit against overload, current leakage and even electrocution.
3. During a malfunction and for the duration of the malfunction, we will have the ability to turn off only one faulty circuit, such as in one room, and not many.

When designing, it is necessary to look at the specifications of the room thermostat

The design of electric underfloor heating also focuses on the relay output from the thermostat for heating. On it depends the maximum power of the entire installation. Most often you can find thermostats with a relay from 12 to 16A. This is the limit of power that can be connected to the thermostat.

With a mains voltage of 230 V AC, we calculate:

• Amps x Line voltage = Maximum power of the heating mat / heating cable.
• 12 A x 230 V = 2,760 W.
• 13 A x 230 V = 2,990 W.
• 14 A x 230 V = 3,220 W
• 15 A x 230 V = 3,450 W
• 16 A x 230 V = 3,680 W.

Example: we can connect one, two or even three heating mats with a maximum heating power of 2990 W to the 13 A relay output. Exceeding this value can quickly damage the thermostat and invalidate the warranty terms with the manufacturer. This can be remedied by installing an additional external auxiliary contactor. How to connect a floor thermostat with an additional contactor? If you think about it, a better and simpler solution for larger areas is to use two separate thermostats.

Thermostat on the wall as a separate component or in a frame system?

Photo TECH CONTROLLERS

When designing the interior of your dream home, it is useful to know what options are available on the market in terms of frame design. Some companies offer only separate thermostats in a fixed housing, but there are also those that can be integrated into other frames. What does such a solution consist of? The front of the thermostat can be combined with frames for light switches or other switches. This significantly affects the appearance of the thermostat and the entire room. The most common such combination is the thermostat and light switch. Make sure the switch is on the side of the door, as it will be closer to your hand and will be used more often. On the other hand, in the evening, when reaching for the switch in the dark, such an arrangement will prevent accidental changes to the thermostat.

For example, the SENZ WIFI room thermostat fits the following frame systems: Berker Q1, Q3; M-Plan, M-Pure, M-Elegance; Ospel Sonata; GIRA E2, E3, 55, Esprit. Silver and anthracite fronts and frames can be purchased in our store. Full list of compatible frames.

What kind of power cord for the floor thermostat?

Knowing the power of the heating circuit in watts, we can (based on the relevant formulas) calculate the thickness of the power cord to its load and length. The exact formulas are required for electrical licensing exams. For ordinary users, however, there is no need to delve into this technical subject. It is enough to know the most common wire thicknesses in underfloor heating systems:

• Heating circuits in the range of up to 3000 watts, the supply wire in the wall with a length of 20 m with a maximum protection of 16 A, the supply wire with a conductor cross-section of 1.5 mm² (three-core).
• Heating circuits in the range of 3000 - 4000 W, power cord in the wall with a length of 20 m with a maximum protection of 20 A, we use a power cord with a conductor cross-section of 2.5 mm² (three-core).

IMPORTANT: It is not recommended to directly connect the 2.5 mm² power cable to the terminals of the thermostat. Copper wire that is too stiff and thick may not fit into the thermostat terminals or cause damage to their mounting solders to the electronic board when pressing into the flush-mounted box. The solution is to replace the wire-type wires with 1.5mm² wire-type wires in the box.

Do you use bushings for the power wire?

Electrical pull-down terminals - there is no need to use additional "furrel" collets for the power cable type.

Terminal sleeve (ferrul)

The use of terminal sleeves (ferrules) on the power cord when connecting a room thermostat depends on the type of terminals used in the thermostat. Here are recommendations for different types of terminals:

• Screw-type electrical terminals: With screw-type terminals, it is recommended to use collets for the wire type of cable. The sleeves prevent the wire strands from spreading under the pressure of the screw, which provides a more secure and durable connection. The cable wire should be terminated with a ferrule-type sleeve, and then the sleeve should be inserted into the terminal and tightened with a screw.
• Electrical pull-down, spring-loaded and push-in terminals: For pull-down terminals and such as push-in terminals, there is no need for sleeves for the wire cable. These terminals are designed to accept the wire cable directly, providing a solid connection without the need for additional accessories.

What if the thermostat has too small a relay output, and you want one thermostat?

An example of connecting an auxiliary contactor to a room thermostat.

Often in rooms such as a large living room or a kitchen connected to a dining room, we need to connect two heating cables under one thermostat, and their combined heating power exceeds the power of our relay in the thermostat. In this case, a separate contactor, the so-called auxiliary contactor, should be installed. It should be installed in the electrical switchboard. This means that it should be planned already at the design stage of the heating system. It will also be necessary to arrange the electrical wiring from the switchboard to the thermostat differently. Usually NO (normally open) type contactors are used. This means that when connected, it will redirect the current to the heating circuit. This will allow you to turn on the heating power of the system to the required value. How to connect a floor thermostat with an additional contactor?

For large areas, it is better to divide it into smaller heating zones and use more thermostats.

Which flush-mounted box for a floor thermostat?

The thermostat for proper operation in the room must be located at a height of about 120 - 150 cm from the floor level in a permanently exposed place.

• It must not be covered with furniture or a curtain.
• It must not be exposed to harsh sunlight.
• It must not be near heat sources such as a radiator, TV, fireplace.
• It must not be placed in a place where there may be large and frequent drafts.

To install a room thermostat without problems, it is necessary to install a standard Ø 60 mm box with a depth of min. 60 mm. In addition to the space for the flush-mounted part of the thermostat, which usually takes up 20-30 mm, you need to add space for the power wire, temperature sensor wire and protective wire connector. Insert all wires as close as possible to the rear cutoff of the box.

NOTE: Always place all wires as close as possible to the back of the box.

What from the thermostat box to floor level?

To the box where the room thermostat will be placed, two installation pipes with an inside diameter of min. 18 mm:

1. In the first to pull the supply wire from the heating cable (with more wires, consider a correspondingly thicker conduit),
2. And to the dedicated tube from the floor temperature sensor. How to install the temperature sensor in the heating mat?

What kind of fuse for floor heating?

In addition, it is necessary to install a suitable residual current disconnector and overcurrent protection in the installation. The selection of fuses depends on the type of supply to the floor heating circuit. On this topic, you can read in the article: what fuse for a heating mat?

Will room thermostats use a Wi-Fi connection?

Modern thermostats also have the ability to control electric floor heating via a smartphone app. If you want to provide this capability, design a WiFi network in advance and make sure the entire house has strong enough home network coverage in every room.

The above description is for informational purposes. Electrical installations should be performed by a licensed person.