WO2011151516A2

WO2011151516A2 - Thermostat

Info

Publication number: WO2011151516A2
Application number: PCT/FI2011/050500
Authority: WO
Inventors: Jari SIEVÄNEN; Teemu Lindqvist
Original assignee: Energate Oy
Priority date: 2010-06-02
Filing date: 2011-05-31
Publication date: 2011-12-08
Also published as: WO2011151516A3

Abstract

A thermostat equipped with a residual current device, comprising a relay (206), a connector (202), a capacitor (208), a circuit breaker (204), and a measurement coil (308). The thermostat comprises at least two printed circuit boards (PCB), a first PCB (20) and a second PCB (30). The relay (206), the connector (202) and the circuit breaker (204) are connected to the first PCB (20) and the measurement coil (308) is connected to the second PCB (30).

Description

THERMOSTAT

FIELD OF THE INVENTION

The present invention relates to a thermostat according to the preamble of the ap- pended independent claim.

BACKGROUND OF THE INVENTION

One way to provide heating for a house or for a room in a house is with floor heating systems using electricity. Electric floor heating systems are typically installed in kitchens, bathrooms or in rooms that require additional heat (such as a cold basement, an addition or a kids' playroom). A floor heating system can be implemented by installing heating elements underneath the floor surface. Electric heating elements are supplied in several different forms. They can be one long continuous length of cable with the installer having to weave the cable up and down the floor at a pre-determined spacing and making a return loop to complete the circuit, or they can be provided in a mat form, where the heating element is preformed in a mat that rolls out onto the floor. Some high voltage cables have a built in return, meaning that a person installing the cable has one end to connect. Some technologies consist of a loop with a start and end. In addition to the heating elements the system might consist of a heating thermostat unit, a sensor or a sensor cable and wires connecting the heating element to the thermostat unit and the sensor or the sensor cable to the thermostat unit.

A sensor is often installed in the floor for heat measurement purposes. The sensor can be for example a Negative Temperature Coefficient (NTC) resistor whose re- sistance decreases as the temperature increases. The sensor is connected with wires to thermostat electronics in the thermostat unit. The thermostat unit typically switches heat elements on/off using relays depending on the temperature of the floor and setting in the thermostat. Additionally or alternatively, the thermostat may comprise a sensor to measure room temperature from air of the room. In many countries electrical regulations and standards set that all electrical under- floor heating systems must be protected by a residual current device (RCD), typically having a rated residual current not exceeding 30 mA. A RCD is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor.

A RCD can be installed to a floor heating system as a separate unit or it can be attached to a thermostat. One floor heating thermostat provided with a fault- current protector is described in patent application EP 1953459A2. According to the patent application, the thermostat and fault-current protector are independent elements integrated together. Because of this overlapping structure, the described thermostat is however relative tall in size with total depth of about 46 millimetres being big to fit in standard wall mount box with depth of about 45 millimetres. In addition wires for electricity and a sensor require additional space in a wall mount box leading to design in which thermostat upper level from a wall surface can be more than 15-25 millimetres. Additionally, installation of the thermostat is laborious since a cable from a temperature sensor needs to be passed through the fault current protector so that the cable can be connected to the thermostat.

SUMMARY OF THE INVENTION

In accordance with aspects of the present invention, there is provided a structure for reducing size of a residual current protected thermostat.

At least some embodiments of the invention provide layout for placing electrical components in a control unit.

This is achieved by a combination of features recited in the independent claim. Accordingly, dependent claims prescribe further detailed implementations of the embodiments of the present invention.

Features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Figure 1 is a schematic diagram showing a thermostat unit, a cover and a wall where the thermostat unit can be installed, figure 2 is a schematic picture showing a wall mount installed thermostat unit, figure 3 is a schematic layout picture showing a first printed circuit board and some of the components in one side of the board, figure 4 is a schematic layout picture showing a second printed circuit board and some of the components in one side of the board, figure 5 shows a schematic picture of a thermostat unit from front and two sides, figure 6 shows a photo of a thermostat unit according to an embodiment with a ruler to demonstrate size of the unit, figure 7 shows a photo of a second printed circuit board of an example em- bodiment, figure 8 shows a photo of a first printed circuit board of an example embodiment, figure 9 shows a photo from side of a thermostat unit of an example embodiment, figure 10 shows a photo of an example implementation of an embodiment, figure 1 1 shows a schematic wire diagram of a thermostat, and figure 12 shows a schematic exploded view of a possible construction of a floor heating thermostat including mechanics.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to Figure 1 , one embodiment of the invention would be applicable as a wall mount installed thermostat unit 1 as shown in the Figure 1 . The thermostat unit 1 according to embodiments of the invention comprises two printed circuit boards (PCB) 20 and 30. In example embodiments the PCBs 20 and 30 are two layer PCBs with components in both sides of the circuit boards, but it is also possible that in some embodiments one of the PCBs is one-sided. For explanatory purposes the PCB 20 is referred as a first PCB and the PCB 30 as a second PCB in the exemplary embodiments. Additionally terms of orientation, such as "top" and "bottom" refer to the orientation of a device as seen in the drawings and does not limit its orientation in use.

The thermostat unit 1 is dimensioned preferably in such a way that it can fit in a standard wall electrical box 10 with an inner free diameter of 50-55 mm and an outer diameter of 70-75 mm, depending on country specific standards. The box 10 can be installed in a wall 12 by making a hole in wall outer surface 12 and by inserting the box in the hole. Alternatively, the box 10 may be installed to the wall structure before installing the outer surface. The box 10 might be connected to some structural elements (not shown) of the wall with screws 14. The box 10 might have metal or plastic parts 102 enabling to adjust the thermostat unit 1 in the box firmly. Additionally or alternatively, the thermostat unit might have holes in it to enable to use for example screws to secure the unit in the box 10. Such holes are typically in the base cover of the thermostat. In an embodiment there is a cover 3 which can be placed on the thermostat unit to cover the box 10 and also provide means for adjusting temperature and for example pressing a fault-current button if needed.

Figure 2 shows an installed thermostat unit 1 in an installation box 10. It is appreciated from the figure 2 that at least some embodiments of the invention enable to construct a fault-current, i.e. residual current, protected floor heating thermostat in a way that the thermostat sticks out 10-20 mm less compared to current solutions with a wall 12 surface bringing clear benefits over prior art. There is a plurality of wires 40 connected to a connector in a first PCB 20 of the thermostat unit 1 as schematically shown in figure 2. Embodiments of the invention are not limited to a wall mounted box but the described structure of the thermostat unit 1 also enables to build relatively slim design for a surface mount thermostat as well.

An exemplary structure of a thermostat and layout of components in a first PCB 20 and a second PCB 30 is presented by referring to Figure 3 and Figure 4.

A connector 202 in the first PCB 20 can be for example a 7-pin connector such as MVE25 from Euroclamp™. Wires 40 going out/to the thermostat 1 can be con- nected to the connector 202. According to at least some embodiments main power to a heating system consisting of the thermostat unit 1 and heating elements and a floor sensor is fed through the connector 202 pin X7 (Live (L)) and X6 (Neutral(N)). Typically nominal voltage in Europe is of about 230 VAC with 50 Hz. In some areas such as North America nominal voltage is about 1 10 VAC with 60 Hz. The connector 202 provides also electricity to a heating element for example via pins X5 and X4 if a controlling relay 206 is switched on. The controlling relay 206 can be for example the relay RT334024 from Tyco Electronics™ capable of switching on and off currents/voltages of 16A/250VAC. The relay 206 is preferably assembled in a circuit board in such a direction that a switching part i.e. high volt- age part is closer to the connector 202. In this case a control signal is routed in a lower part of the PCB from the direction of Figure 3 point of view. This enables electrical design for the first PCB 30 in such a way that high voltage electronics are placed mostly in a second left corner of the PCB from direction of figure 3. In an embodiment the relay is controlled by Microcontroller IC (integrated circuit) 302 based on measurements from a sensor. Microcontroller IC 302 can be for example NXP™ microcontroller such as LPC1 100 based on ARM™ Cortex-M0 processor with several analogue to digital (AD) converters among other features. Said AD converters are used to determine temperature level by measuring current feed through a NTC in a sensor in respect to a reference temperature level settable by an adjustable resistor 304 in the PCB 30. A control signal from IC 302 to the relay can be fed to the first PCB 20 via a connector 216. Signal to sensor can be fed via the connector 216. In an embodiment of the invention a floor sensor is preferably connected to pins X1 and X2 of the connector 202 in order to place those to maximum distance from mains power (connected to X7 and X6). Additional benefit of enabling connecting of the temperature sensor to the connector 202 is that installation of the thermostat is easy compared to prior art solutions in which the cable from the temperature sensor needs to be manually guided through the residual current device to the thermostat.

Additional components in the first PCB 20 include a capacitor 208 that generates voltage to the thermostat part of the product and miscellaneous components 210 such as capacitors, resistors, transistors, diodes and other active and passive components. Although figure shows components only on one side there can be components in the other side of the PCB 20 and PCB 30 as well.

A key component from fault-current protection point of view is a solenoid switch component 204 attached to the first PCB 20. The solenoid component 204 can be for example WA M2ML Solenoid from Western Automation Research and Devel- opment Ltd. The solenoid switch component 204 is according to at least some embodiments connected in such a way that mains power from pins X7 and X6 is fed first through a measurement coil, which measures residual current, and then through the component 204. In case of fault-current incident a control signal from residual current device (RCD) related electronics disconnects mains power. In one embodiment RCD electronics are contained in the second PCB 30. One way to get a signal from the RCD is via the connector 216.

Residual current device related electronics consists of an integrated circuit 306 for detecting a fault current, a test/measurement coil 308 and miscellaneous passive and active components 310. The circuit 306 can be for example WA05GC from Western Automation Research and Development Ltd. The test/measurement coil 308 can be for example a component from Western Automation Research and Development Ltd. The main power from first PCB 20 connector 202 pins X6 and X7 is fed via pins 324 and 322 to the second PCB 30. Pins 324 and 322 go through the measurement coil 308 as shown in figure 4. Pins 324 and 322 are electrically connected with conductor lines 315 and 314 to pins 214 and 212 respectively. Electricity is fed back to the first PCB 20 via pins 214 and 212 and then connected to the switch component 204 as described earlier. In case of fault- current the circuit 306 triggers the component 204 to switch power off. According to embodiments there is a space 312 between conductor lines 314 and 315 connecting electricity. The space is preferably at least 4 millimetres in order to comply with certain safety standards. The second PCB has preferably a hole 316 (figure 4) to enable usage of a fault-current reset 213 (see figure 5) of the switch 204.

According to at least some embodiments of the invention, PCB 20 and PCB 30 are approximately same size when observed from top. In at least some embodiments PCB boards can be attached together in a "piggy bag" style using for example pins 214, 212, 226, 227 and the connector 216. Said pins might be soldered, before connecting the second and first PCBs together to either second and/or first PCB initially. After final assembly of the second and first PCBs together also other end of the pin might be soldered ensuring better conductivity. A counterpart (designated also as 216) of the connector 216 might be in either the second or first PCB. The connector 216 might have for example 8 pins to enable communication between the second 30 and first 20 PCB. A combination of the second PCB 30 and the first PCB 20 is referred as the thermostat unit 1 in an embodiment. Figure 5 further illustrates the thermostat unit 1 as shown from looking towards the first PCB 30 and from two sides (view A and view B). As it can be seen the second PCB 20 and the first PCB 30 are connected in a stack. In addition to components described earlier there might be for example a switch 326 soldered in other side of the second PCB 30 for example to test fault-current functionality. As it can be seen there can be a mechanical switch 213 connected to the solenoid switch compo- nent 204 for resetting the fault-current switch.

For further clarification on embodiments there is presented in figures 6, 7, 8 and 9 showing photos of an implementation of the invention. As it can be seen from figures 9 and 6 the size of a thermostat unit with an integrated fault-current detector is significantly smaller than in arrangements according to prior art. Figure 10 shows a photo of an example thermostat seen mainly from a direction of the top layer of the second PCB 30 for clarification purposes. The manual resetting pin 213 is accessible via an aperture 316 in the second PCB 30. Figure 1 1 shows a schematic wire diagram of a thermostat. Components which are in the second PCB 30 are drawn inside of a dashed line. Other components are assembled in the first PCB 20. Mains power (L and N) is fed via pins X7 and X6 of the connector 202. Electricity is lead to from the connector 202 to the second PCB 30 and back to the first PCB 20 via the coil 308. The coil 308 is connected to a circuit 306 to detect residual current leakage in the system. As shown in figure 1 1 the circuit 306 provides a control signal to a circuit breaker component 204. In normal operation electricity is fed to a relay 206. The relay 206 is controlled with a microcontroller 302. The microcontroller 302 is connected via pins X1 and X2 to a sensor measuring floor temperature. Pins X4 and X5 are used to provide electricity to a heating element.

Figure 12 shows a schematic exploded view of a possible construction of a floor heating thermostat including mechanics. A bottom cup 510 is typically installed in an electrical box 10. A middle cover 508 can be used to increase a surface and air gap to electrical components of the PCB boards 20 and 30. A knob 506 can be used for turning the variable resistor 304 in order to set up a desired temperature. Parts 500, 502 and 504 are decorative covers for the thermostat. The parts 500, 502, 504, 506 and 508 together might form the cover 3 of Figure 3.

A typical thermostat according to the invention is equipped with a residual current device and comprises at least two printed circuit boards (PCB), a first PCB 20 and a second PCB 30. In a typical thermostat according to the invention the relay 206, the connector 202 and the circuit breaker 204 are connected to the first PCB 20 and that the measurement coil 308 is connected to the second PCB 30. In at least some embodiments of the invention residual current detection logic components are attached to the second PCB 30. The residual current detection logic components comprise at least a circuit 306 such as a circuit WA05GC from Ward Industries™ or similar, which circuit is connected to the measurement coil 308. This component layout enables a very compact thermostat structure.

At least in some embodiments of the invention a temperature control logic is connected to the second PCB 30. Also the capacitor that is arranged to generate voltage to the thermostat circuit is located on the first PCB 20.

In at least some embodiments of the invention, the connector 202 comprises a plurality of connector pins to connect at least a load cable, a floor temperature sensor cable, a temperature reduction signal and heating cable connection to the thermostat. Having all external cable connections in one part of the thermostat with easy access, installation of the thermostat to use is made easy and fast.

As mentioned above, PCBs used may have components in one side or both sides of a board. According to at least some embodiments of the invention, the first PCB 20 comprises a bottom layer 230 and a top layer 232 and that the second PCB 30 comprises a bottom layer 330. The terms bottom layer and top layer indicate in this context that the bottom layer is on one side of a board and the top layer is on another side of the board. The bottom layer 330 of the PCB 30 faces the top layer 232 of the first PCB 20 and the top layer 332 of the PCB 30 faces away from the first PCB 20. The relay 206, the connector 202 and the circuit breaker 204 are connected to the bottom layer 230 of the first PCB 20 and the measurement coil 308 is connected or located between the bottom layer 330 of the second PCB 30 and the top layer of the first PCB 20. At least in some embodiments an adjustable resistor 304 for temperature level setting is connected to the second PCB 30. The adjustable resistor 304 is in at least some embodiments of the invention connected to the bottom layer 330 of the second PCB 30, i.e. to between the first PCB 20 and the second PCB 30 so that the resistor does not increase total height of the thermostat. To enable adjustment of the resistor, the second PCB 30 comprises an aperture for a lever extending through the cover 3 to get connected to the adjustable resistor 304 through the second PCB 30 and the cover 3.

According to at least some embodiments of the invention, the first PCB 20 and the second PCB 30 are connected electronically with two pairs of connector leads to lead high voltage between the first PCB 20 and the second PCB 30 to create a loop for high voltage from the first PCB 20 to the second PCB 30 and back. In some embodiments of the invention this said loop does not have any other purpose but to go through a measurement coil so that residual current, i.e. a malfunc- tion of a heating system can be detected. Additionally the thermostat comprises a pair of connector leads 226 and 227 to lead operating voltage for the RCD circuit from the first PCB 20 to the second PCB 30. Furthermore, a plurality of additional connector leads 216 lead low voltage and control data between the first PCB 20 and the second PCB 30. According to at least some embodiments of the invention, the circuit breaker 204 comprises a movable frame member 234. The movable frame member comprises metallic connectors which are arranged to move to and from against fixed contacts connected to the bottom layer 230 of the first PCB 20 by control of a solenoid 236 attached to the first PCB 20. As mentioned above, one suitable circuit breaker, i.e. a solenoid switch component, to be used in the embodiments of the invention is WA M2ML Solenoid from Western Automation Research and Development Ltd. Additionally the circuit breaker 204 may comprise a manual resetting pin 213 of the circuit breaker. The manual resetting pin 213 is arranged to extend through an aperture 316 in the second PCB 30 as well as through the cover 3 so that it can be used, e.g. by pushing, from outside of the thermostat.

According to some embodiments of the invention the top layer 332 of the second PCB 30 comprises a testing push button 326 to test residual current detection functionality of the thermostat. This enables testing that the residual current detection and the circuit breaker 204 work as they should. A thermostat according to at least some embodiments of the invention comprises a green led and red led to indicate operational status of the controlling relay 206. The green led and the red led are preferably connected to the top layer 332 of the second PCB 30.

In some embodiments of the invention, main power from the connector 202 pins X6 and X7 is fed via first connector leads 324, 322 to the second PCB 30, the first connector leads 324 and 322 being arranged to go through the measurement coil 308 and to electrically connect via conductor lines 314 and 315 of the second PCB 30 to second connector leads 214, 212 and back to the first PCB 20 via the second connector leads 214, 212 and then fed to the circuit breaker 204 connected to the first PCB 20. This novel structure and layout enables residual current detection and circuit breaking effectively and reliable in a very small space and fulfilling safety requirements.

At least in some embodiments of the invention, the first connector leads 322 and 324 are actually long pins from the connector 202 and the second connector leads 212 and 214 are rigid, metal pins. The connector leads can be made of steel, copper or some other suitable metal with high conductivity. It should also be noted that the first and second connector pins may be made of different material. Length of the first connector leads 322 and 324 and the second connector leads 212, 214 in at least some of the embodiments of the invention is 12-20 mm. At least in some embodiments, the first connector leads 322 and 324 and the second connector leads 212 and 214 are arranged parallel to each other.

According to at least some embodiments of the invention, the first connector leads 322 and 324 are arranged so that distance between the connector leads is greater or equal to 4mm. Similarly the second connector leads 212 and 214 are arranged so that distance between the connector leads is greater or equal to 4mm. Having said distance as greater or at least equal to 4 mm, it is possible to reduce a risk of electrical breakdown between connector leads.

At least in some embodiments of the invention, the first connector leads 322 and 324 are part of the connector 202 and arranged to extend through the first PCB 20. This reduces the number of soldered contacts needed and thus heat generation and voltage drops are reduced.

According to at least some embodiments of the invention the first connector leads 322 and 324 and the second connector leads 212 and 214 have been fixed to the first PCB 20. The first connector leads 322 and 324 and the second connector leads 212 and 214 have been further arranged to connect electronically to the second PCB 30 by extending through apertures in the second PCB 30 so that electrical fittings are formed between edges of the apertures and the connector leads 322, 324, 212 and 214.

Distance between a top layer 232 of the first PCB 20 and a bottom layer 330 of the second PCB 30 is at least in some embodiments of the invention 7-1 1 mm. This distance enables fitting of components to a space between the first PCB 20 and the second PCB 30 and still enable compact total height of the thermostat.

As mentioned above, according to at least some embodiments of the invention the thermostat comprises a first printed circuit board (PCB) 20 into which the relay 206, the connector 202 and the circuit breaker 204 are located and a second PCB 30 into which the measurement coil 308 is located and that the relay 206, the connector 202 and the circuit breaker 204 are connected to the first PCB 20. According to at least some embodiments, the relay 206 is connected next to the connec- tor 202 so that contacts of the relay are facing the connector. This layout structure reduces length of high voltage connections in the first PCB and thus reduces heat generation in the thermostat.

According to at least some embodiments of the invention, the relay 206 is located on the first PCB 20 between the capacitor 208 and the circuit breaker 204. Advan- tage of this layout is that the relay 206 and the circuit breaker 204 are next to each other so that high voltage components are close to each other thus reducing length of high voltage connections in the first PCB.

At least in some embodiments of the invention, a distance between the relay 206 and pins of the connector 202 to which the relay 206 is connected is less than 8 mm.

According to an embodiment of the invention the thermostat is a floor heating thermostat. It should be understood that a similar structure can be used for other thermostats requiring fault-power protection than a floor thermostat. As an example a similar structure could be used for a thermostat controlling electrical radiators in a house.

Further embodiments of the invention include adding a room temperature sensor preferably on the second PCB 30. Embodiments of the structure enable said sensor to work accurately since it is located as far as possible from the heat that is generated in the first PCB 20. In addition power components such as the relay 206 are far away from the inbuilt temperature sensor enabling more accurate operation.

Additionally the second PCB 30 might include light emitting diodes (LEDs) to be shown for users of the thermostat unit via for example an opening in the cover 3 or for example a transparent part in the cover 3. Additionally for example microcontroller IC 302 might include or might control a wireless or wired communication unit. Said unit could be used for remote monitoring and controlling of the thermostat unit. An example of a wireless communication unit is BlueTooth or Wireless Local Area Network. An example wired communica- tion protocol to be used is Local Area Network over power lines or a dedicated communication network like Ethernet.

It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1 . A thermostat equipped with a residual current device, the thermostat comprising a relay (206), a connector (202), a capacitor (208), a circuit breaker (204), and a measurement coil (308), characterized in that the thermostat comprises at least two printed circuit boards (PCB), a first PCB (20) and a second PCB (30), and that the relay (206), the connector (202) and the circuit breaker (204) are connected to the first PCB (20) and that the measurement coil (308) is connected to the second PCB (30).

2. A thermostat according to claim 1 , characterized in that residual current detec- tion logic components are attached to the second PCB (30).

3. A thermostat according to claim 2, characterized in that the residual current logic comprises a circuit (306) to measure a residual current in the measurement coil (308) and the circuit (306) is connected to the measurement coil (308).

4. A thermostat according to any of the preceding claims, characterized in that temperature control logic is connected to the second PCB (30) and the capacitor that is arranged to generate voltage to the thermostat circuit is located on the first PCB (20).

5. A thermostat according to any of the preceding claims, characterized in that the connector (202) comprises a plurality of connector pins to connect at least a load cable, floor temperature sensor cable, temperature reduction signal and heating cable connection to the thermostat.

6. A thermostat according to any of the preceding claims, characterized in that the first PCB (20) comprises a bottom layer (230) and a top layer (232) and that the second PCB (30) comprises a bottom layer (330) facing the top layer (232) of the first PCB (20) and a top layer (332) facing away from the first PCB (20), and that the relay (206), the connector (202) and the circuit breaker (204) are connected to the bottom layer (230) of the first PCB (20) and that the measurement coil (308) is connected or located between the bottom layer (330) of the second PCB (30) and the top layer (232) of the first PCB (20).

7. A thermostat according to claim 6, characterized in that distance between the top layer (232) of the first PCB (20) and the bottom layer (330) of the second PCB (30) is 7-1 1 mm.

8. A thermostat according to any of the preceding claims, characterized in that an adjustable resistor (304) for temperature level setting is connected to the second PCB (30).

9. A thermostat according to claim 8, characterized in that the adjustable resistor (304) is connected to the bottom layer (330) of the second PCB (30) and that the second PCB (30) comprises an aperture for a lever to get connected to the adjustable resistor (304) through the second PCB (30).

10. A thermostat according to any of the preceding claims, characterized in that the first PCB (20) and the second PCB (30) are connected electronically with two pairs of connector leads to lead high voltage between the first PCB (20) and the second PCB (30) and with a plurality of additional connector leads to lead low and high voltage and control data between the first PCB (20) and the second PCB (30).

1 1 . A thermostat according to any of the preceding claims, characterized in that main power from the connector (202) pins (X6, X7) is fed via first connector leads

(324, 322) to the second PCB (30), the first connector leads (324, 322) being arranged to go through the measurement coil (308) and to electrically connect via conductor lines (314, 315) of the second PCB (30) to second connector leads (214, 212) and back to the first PCB (20) via the second connector leads (214, 212) and then fed to the circuit breaker (204) connected to the first PCB (20).

12. A thermostat according to claim 1 1 , characterized in that the first connector leads (322, 324) and the second connector leads (212, 214) are rigid, metal pins.

13. A thermostat according to claim 1 1 or 12, characterized in that length of the first connector leads (322, 324) and the second connector leads (212, 214) is 12- 20 mm.

14. A thermostat according to any of the preceding claims 1 1 -13, characterized in that the first connector leads (322, 324) and the second connector leads (212, 214) are arranged parallel to each other.

15. A thermostat according to any of the preceding claims 1 1 -14, characterized in that the first connector leads (322, 324) are arranged so that distance between the connector leads is greater or equal to 4 mm and that the second connector leads (212, 214) are arranged so that distance between the connector leads is greater or equal to 4 mm.

16. A thermostat according to any of the preceding claims 1 1 -15, characterized in that the first connector leads (322, 324) are part of the connector (202) and arranged to extend through the first PCB (20).

17. A thermostat according to any of the preceding claims 1 1 -16, characterized in that the first connector leads (322, 324) and the second connector leads (212,

214) have been fixed to the first PCB (20) and the first connector leads (322, 324) and the second connector leads (212, 214) have been arranged to connect electronically to the second PCB (30) by extending through apertures in the second PCB (30) so that electrical fittings are formed between edges of the apertures and the connector leads (322, 324, 212, 214).

18. A thermostat according to any of the preceding claims, characterized in that the relay (206) is connected next to the connector (202) so that contacts of the relay are facing the connector.

19. A thermostat according to any of the preceding claims, characterized in that the relay (206) is located on the first PCB (20) between the capacitor (208) and the circuit breaker (204).

20. A thermostat according to any of the preceding claims, characterized in that a distance between the relay (206) and pins of the connector (202) to which the relay (206) is connected is less than 8 mm.

21 . A thermostat according to any of the preceding claims, characterized in that the circuit breaker (204) comprises a movable frame member (234), the movable frame member comprising metallic connectors and arranged to move to and from against fixed contacts connected to the bottom layer (230) of the first PCB (20) by control of a solenoid (236) attached to the first PCB (20).

22. A thermostat according to any of the preceding claims, characterized in that the circuit breaker (204) comprises a manual resetting pin (213) of the circuit breaker, the manual resetting pin (213) being arranged to extend through an aperture (316) in the second PCB (30).

23. A thermostat according to any of the preceding claims, characterized in that the top layer (332) of the second PCB (30) comprises a testing push button (326) to test residual current detection functionality of the thermostat.

24. A thermostat according to any of the preceding claims, characterized in that the top layer (332) of the second PCB (30) comprises a green led and red led to indicate operational status of the controlling relay (206).

25. A thermostat according to any of the preceding claims, characterized in that the thermostat is a floor heating thermostat.