The present invention relates to a hot water appliance. Conventional systems for central heating (CH) of buildings comprise a central boiler in which a burner combusts gas. The heat released during combustion is

transferred to water using a heat exchanger. A pump in the boiler pumps the heated water through a pipe system in the building to radiators, which radiators transfer the heat of the water, mainly through radiation and convection, to the room in which the radiator is disposed. Via return conduits the cooled water once again reaches the boiler where the water is heated.

The boiler is controlled from a thermostat. The

thermostat is arranged in one of the rooms to be heated. The thermostat comprises a temperature sensor and an operating member for setting a desired temperature. The thermostat originally consisted of a bimetal switch or mercury switch which sent an on/off signal to the boiler. Temperature- dependent electronic components are used nowadays as

temperature sensor. Modern thermostats further no longer generate an on/off signal but transmit a modulated signal to the boiler to enable indication of a variable heat demand. Modern thermostats are further often provided with a clock so that the thermostat can also follow a time-dependent program. For historical reasons these thermostats do however still communicate with the boiler over a two-wire

connection. Although this is not an insurmountable problem, it does impose a number of limitations. For reasons of compatibility the thermostat has to have its own power supply (generally a battery) and transmitting additional information, in addition to the heat demand, over the two- wire connection entails overhead and costs.

US 2010/045470A1 describes a steam distribution system for heating a building with different dwellings. This system is based on remote-controlled steam valves on the radiators in the dwellings. The operation takes place on the basis of the temperatures measured in the dwellings and set

temperatures which can optionally be entered via a

thermostat in the dwelling. There is a central control system which, in addition to controlling the steam valves, also remotely controls switching on and off of a steam boiler. This central control communicates wirelessly with the valves and with the steam boiler via a local network.

DE 102 29 222 Al very generally describes a central control system which operates all technical installations in a building on the basis of measurements by sensors in order to thus minimize the energy consumption. It is not stated exactly how a hot water appliance present in the system is controlled.

A central control of technical equipment in a dwelling or other building is also described in O01/13577 A2. The control makes use of networks in the building. Few specific details are described in respect of the heating and hot water supply. There is however a central thermostat which communicates with a hot water appliance via the network.

The present invention has for its object to take a subsequent step in the development of heating boilers which provides a new range of functionalities.

This object is achieved by providing a hot water appliance comprising: a heating member for heating water; a control unit for controlling the heating member, the control unit comprising a memory for storing a desired temperature of a space to be heated, and an input/output unit connected to the control unit; wherein the input/output unit is adapted to receive a signal representative of a measured temperature; and wherein the control unit controls the heating member on the basis of the desired temperature and the measured temperature. The present invention is based on the insight that the control unit, i.e. the controller in terms of control engineering, does not belong at the location of the temperature sensor but at the location of the boiler. This has of course developed historically in this way because the temperature sensor and the controller were a single physical component in conventional

thermostats. The introduction of electronic temperature sensors, such as for instance temperature-dependent

resistors, resulted in thermostats with separate components on the one hand for detecting the temperature and on the other for determining the control action. Due to the nature of a CH-installation, i.e the central generation of heat, which heat is then distributed over the different locations in the house where there is a heat demand, there is

something to be said for having the heat demand determined at the boiler. Compared to a conventional CH-installation the controller therefore has to be removed from the

thermostat and displaced to the CH boiler. In the first instance the conventional thermostat is hereby relegated to being a temperature sensor and operating device. The

"thermostat" determines a deviation on the basis of the ' measured temperature and the set temperature, and transmits this to the boiler. In the boiler the control unit

determines the control action associated with the deviation for the purpose of driving the heating member. (In most cases, the heating member is controlled by controlling the rotation speed of a fan which draws in the air with which gas is combusted in a burner.)

However, by going a step further than mere physical displacement of the controller (the control unit) , a greater range of options is created. This further step is also determining the deviation in the control unit (in the boiler) . ^c The conventional thermostat is hereby relegated to being just a temperature sensor. The advantages hereof are discussed with reference to embodiments below. Although it is not strictly necessary to incorporate the control unit in the housing of the hot water appliance, this is recommended.

The space to be heated is not necessarily limited to a single room. Traditionally present in for instance dwellings is only a single thermostat, with which the temperature is measured in a single room and on which only a single desired temperature can be set. In these cases the CH installation however heats more than one room. Although the temperature of the room in which the thermostat is hung is probably the temperature closest to the set desired temperature most of the time, the same thermostat is used to "control" the temperature in the other rooms. Similarly, the term space in the present invention must not be understood as being limited to a single room. A space can comprise one or more rooms. In some cases a space can even comprise only a part of a room, for instance in the case of a long hallway with much heat loss, wherein the two ends of the hallway are heated by their own radiator with their own control circuit.

The measured temperature need not necessarily be the temperature in a room. In so-called weather-dependent temperature controls use is made of an outdoor thermometer and a feed forward controller. The feed forward controller determines the control action on the basis of the outside temperature, a (presumed) known effect of the interference (outside temperature) and a (presumed) known effect of the control action (the operation of the heating member) .

In a further embodiment a hot water appliance is provided, wherein the input/output unit is adapted to receive operating instructions from at least one operating device connected to the input/output unit, and the control unit is adapted to control the heating member on the basis of the received operating instructions. The operating instructions on the basis of which the device is controlled by a user can thus be generated remotely of the hot water appliance .

In a further embodiment of the water appliance

according to the invention the control unit can be adapted to store the received operating instructions in the memory. A program of temperatures desired over a determined period can for instance thus be stored.

In order to prevent the hot water appliance switching off in the unlikely event of the connection between the input/output unit and the operating device being broken, it is recommended that a preset desired temperature or a predefined program for a desired temperature is stored in the memory and that the control unit is adapted to control the heating member on the basis of respectively the preset temperature or the predefined program when no operating instructions have been respectively received or stored. The control unit thus has a configurable control algorithm, whereby the hot water appliance can function independently on the basis of stored standard settings (default) , although the configuration of the of the control can be modified via an operating device which communicates with the input/output unit .

In a specific embodiment the input/output unit

comprises a two-contact inlet/outlet for two-way

communication with an operating device with integrated temperature sensor. The input/output unit is adapted to send and receive messages via the two-contact inlet/outlet according to a protocol suitable for two-way communication on a two-wire connection and for multiplexing messages from the operating device and the temperature sensor. In an alternative, specific embodiment the input/output unit is adapted such that use is made of two physically separated one-way connections. In another alternative, specific embodiment the input/output unit is adapted such that use is made of two physically separated connections for the temperature sensor and the operating device. In another alternative, specific embodiment the input/output unit is adapted such that use is made of three physically separated one-way connections: one for input of messages from the temperature sensor, one for input of messages from the operating device and one for output of messages from the operating device.

In a further embodiment a hot water appliance is provided, wherein the input/output unit further comprises a network coupling unit for exchanging data over a network. By incorporating a network coupling unit in the input/output unit it is possible to couple components, such as for instance the temperature sensor or the operating device, to the control unit over a network connection, for instance a pre-existing home LAN or office LAN. Such a LAN is

preferably based on TCP, UDP and IP protocols over Ethernet.

In a further embodiment the present invention provides a hot water appliance, further comprising a web server for making a user interface available via the network coupling unit for the purpose of operating the hot water appliance. In yet another embodiment the invention provides a hot water device, wherein the user interface made available by the web server is accessible via the network coupling unit. In yet another embodiment the invention provides a hot water appliance, wherein the user interface is adapted to allow the user to perform at least one of the following actions: entering a desired temperature; entering a program for a desired temperature; viewing a measured temperature; viewing status information relating to the hot water appliance;

viewing maintenance information; viewing error messages;

viewing performance data; and adjusting the hot water appliance. By means of the incorporated web server it is possible to navigate to the web server of the hot water appliance using for instance the browser of a smartphone. The user is then shown a user interface with which the user can operate or program the hot water appliance or view information. It is thus possible for instance to view the temperature measured by the connected temperature sensors, enter or change a desired temperature for a space, enter or change a program for the temperature variation during the day or week, set or activate a holiday program, read status information or maintenance information.

The obvious manner of enabling operation via a network from a prior art installation would be to provide a

conventional thermostat (with integrated temperature sensor, operating means and controller) with a network interface and an incorporated web server.

A further embodiment according to the invention

provides a hot water appliance, wherein the input/output unit comprises a wireless communication device. In a

specific embodiment the communication device makes use of one of the WiFi protocols. The communication device can serve as a WiFi access point. Alternatively, the

communication device is however a WiFi client which connects to an existing WiFi access point. In this configuration the hot water appliance forms part of the LAN with which the WiFi access point is associated, and temperature sensors and operating devices can be connected via the existing LAN to the hot water appliance. In other alternative embodiments use is made of WiFi Ad Hoc or Direct WiFi to connect the temperature sensors and operating devices.

In yet another embodiment the invention provides a hot water appliance, wherein the operating device can be

connected via the wireless communication device to the control unit. The operating device is not limited here to specialized dedicated operating devices, but mobile phones with a dedicated application installed, mobile phones which, as described above, make contact via their web browser with a web server incorporated into the hot water appliance, and personal computers which make contact via a web browser with the web server can also be envisaged.

The invention further provides a hot water appliance, wherein: the memory is adapted to store a desired

temperature for two or more spaces to be heated; and the control unit is adapted to control the heating member on the basis of the desired temperature in the two or more spaces to be heated and the measured temperature. In this

embodiment the control unit has two or more target

temperatures (the desired temperatures) and a single

measured temperature and a single measured value. The single measured value can be the temperature in one of the spaces for which a desired temperature is stipulated, although it is also possible for the measured temperature to be a different temperature, such as for instance an outside temperature in the case of a weather-dependent temperature control. There are also two or more target temperatures here. In the case the hot water appliance has a plurality of independent hot water circuits and each of the desired temperatures substantially corresponds to an individual hot water circuit, it is then relatively easy to control each hot water circuit separately in order to realize the

different desired temperatures. If this is not the case, the control unit will have to reach a form of compromise, for instance by allowing a tolerance at the desired temperature or by using desired temperature ranges instead of desired temperatures. Alternatively, a weighting can be used to indicate a preference between the desired temperatures. If there are more desired temperatures than measured

temperatures, it is in addition necessary for the control unit to be able to estimate with a certain degree of

reliability the actual temperature of the spaces for which the desired temperature is entered but for which no measured temperature is available. In yet another embodiment the invention provides a hot water appliance, wherein: the input/output unit is adapted to receive two or more signals which are each representative of a measured temperature; and the control unit is adapted to control the heating member on the basis of the desired temperature in the space to be heated or the desired

temperatures in the two or more spaces to be heated, and the two or more measured temperatures. In a specific embodiment the temperature signals are provided to the input/output unit via a wired connection. In a specific alternative embodiment the temperature signals are provided wirelessly to the input/output unit. In yet another specific embodiment the temperature signals are provided via both wired and wireless connections.

In a further embodiment a hot water appliance is provided, wherein: the control unit determines a deviation between a desired temperature in the space to be heated or the two or more spaces to be heated and the measured

temperature or temperatures and applies a weighting to the deviations for the purpose of controlling the heating member. This is particularly recommended when there are more spaces with associated desired temperatures than there are independent hot water circuits. Through the weighting it is possible to give priority to specific desired temperatures, since the actually realized temperatures in the spaces with a corresponding temperature are not independent of each other.

In yet another embodiment the invention provides a hot water appliance, further comprising a notification member for sending a notification via the communication device. The notification can for instance comprise a error message. The notification for instance comprises an e-mail message or an SMS message. In an embodiment according to the invention a hot water appliance is provided, wherein the device comprises a CH boiler or a combi-boiler .

Further advantages and embodiments are discussed hereinbelow with reference to the accompanying figures, in which :

Figure 1 shows a hot water appliance with thermostat according to the prior art;

Figure 2 shows an alternative hot water appliance with thermostat according to the prior art;

Figure 3 shows a hot water appliance according to the present invention;

Figure 4 shows a further embodiment of a hot water appliance according to the present invention;

Figure 5 shows yet another embodiment of a hot water appliance according to the present invention;

Figure 6 shows an alternative embodiment of a hot water appliance according to the present invention;

Figure 7 shows a further alternative embodiment of a hot water appliance according to the present invention;

Figure 8 shows yet another alternative embodiment of a hot water appliance according to the present invention;

Figure 9 is a schematic representation of the control unit and the heating member of the hot water appliance of Figure 8; and

Figure 10 is a flow diagram indicating how the hot water appliance is controlled.

A hot water appliance 10 (figure 1) according to the prior art comprises a feed conduit 22 for water. The water is circulated in the hot water circuit by a pump 24. The water is pumped through a heat exchanger 26, where it is heated. The hot water leaves hot water appliance 10 via water outlet 28. The water in heat exchanger 26 is heated by a burner 30. Burner 30 comprises an air/gas mixture from a mixer 32 (for instance a venturi) . Air is drawn in by a fan 34 via an air feed 36 and blown into mixer 32. Gas from a gas feed 38 reaches mixer 32 via a gas block 39.

Fan 34 and pump 24 are controlled from an external thermostat 50 located elsewhere. Thermostat 50 is connected via a cable 42 to hot water appliance 10. Cable 42 is typically a two-wire connection. Thermostat 50 comprises a temperature sensor 52 which generates a signal to a

controller 54. Controller 54 is further connected to a control panel 56. A desired temperature can be entered and programs set via the control panel. The control panel is generally provided with a display screen on which the measured temperature is shown. The display screen usually also shows information for the purpose of facilitating input of a desired temperature or a program.

Some prior art hot water appliances 10 are provided with a dual conduit to enable realization of two hot water circuits. Hot water circuit 10 of figure 2 shows a first water feed 22a in which the water is pumped by a first pump 24a, after which the water runs via a first heat exchanger 26a to water discharge 28a. The first hot water circuit is hereby provided with hot water. The second hot water circuit feeds water to the second water feed 22b. The water is pumped by second pump 24b and runs via second heat exchanger 26b to second water discharge 28b. Two separated hot water circuits are realized in this way. It is otherwise

advantageous to integrate the first and second heat

exchanger 26a, 26b into a single heat exchanger.

In both hot water appliance 10 of figure 1 and hot water appliance 10 of figure 2 the temperature controller is located in thermostat 50. The controller determines the deviation between the temperature measured by temperature sensor 52 and the desired temperature entered via control panel 56. On the basis of this deviation an indication is given via cable 42 that there is a heat demand and, in the case of a modulated signal, how great the heat demand is. Hot water appliance 100 (figure 3) according to the present invention largely corresponds to the prior art hot water appliance 10. Water is supplied via a water feed 122 and circulated by means of a pump 124. The water is pumped via a heat exchanger 126 to water discharge 128. The water in heat exchanger 126 is heated by a burner 130. The burner combusts an air/gas mixture. Air is drawn in via an air feed 136 by a fan 134 and blown into mixer 132. Gas moves from gas feed 138 via gas block 139 to mixer 132, where it mixes with the air. The controller or control unit 154 which controls fan 134 and pump 124 is however not now

incorporated in thermostat 50 but in hot water appliance 100 itself. This controller 154 comprises a memory 153 in which a desired temperature can be stored and an input/output unit 155 (figure 9) . A housing 150 is connected via a cable 42 to the input/output unit 155 of controller 154 in hot water appliance 100. Housing 150 no longer comprises a controller 54, but only a temperature sensor 152 which provides a signal representative of the temperature. In addition, a control panel 156 is arranged in housing 150. Via this control panel 156 a desired temperature can be entered, which is transmitted via cable 42 to controller 154 in hot water appliance 100 and is there stored in memory 153. Other operating instructions, for instance switch-on and switch- off times in accordance with a program entered via control panel 156, can be transmitted via cable 42 to control device 154, which stores them in memory 153. Two signal lines are drawn in cable 42. These are however not necessarily two physically separated conductors. Depending on the

embodiment, this can for instance also be a data bus.

In an alternative embodiment (figure 4) there are even two temperature sensors 152a, 152b connected to control unit 154 in the hot water appliance. The first temperature sensor 152a is received in the same housing 150a as a control panel 156a and connected to hot water appliance 100 via a first cable 42a. A second temperature sensor 152b is received in a second housing 150b and connected to hot water appliance 100 via a second cable 42b. In a specific embodiment the first housing 150a with the first temperature sensor 152a is located in a room which is heated and where the temperature has to be regulated. The first temperature sensor measures the temperature in the room. The difference from the desired temperature set via control panel 156a is also the deviation which has to be removed by control 154. The second housing 150b with the second temperature sensor 152b is placed outside. The second temperature sensor 152b thus detects the outside temperature. Controller 154 thus uses the signal from the first temperature sensor 152a to remove, by means of a feedback, deviations detected in the inside

temperature, while controller 154 uses the signal from the second temperature sensor 152b to pro-actively respond to temperature changes outside by means of a feed forward coupling. In other embodiments the second temperature sensor 152b is for instance also placed inside, but in a different room from temperature sensor 152a. It is highly probable in this case that another control algorithm will also be necessary .

In another embodiment (figure 5) hot water appliance 100 is adapted to provide two hot water circuits with hot water. Hot water appliance 10 comprises a first water feed 122a. From the first water feed 122a the water is pumped by first pump 124a via the first heat exchanger 126a to the first water discharge 128a. This part forms part of the first hot water circuit. From a second water feed 122b water is pumped by a second pump 124b via the second heat

exchanger 126b to the second water discharge 128b. This part forms part of the second hot water circuit. It is otherwise advantageous to integrate the first heat exchanger 126a and the second heat exchanger 126b into a single heat exchanger with two separated water feeds. In this embodiment, as in the previous one, two

temperature sensors 152a and 152b are connected to the hot water appliance. The first temperature sensor 152a is received in a first space which is heated using the first hot water circuit. The second temperature sensor 152b is received in a second space which is heated using the second hot water circuit. Controller 154 now also has two separated control circuits. The first makes use of the temperature measured by the first temperature sensor 152a and compares this to a first desired temperature set for the first space. On the basis of the deviation this control circuit controls pump 124a of the first hot water circuit (and fan 134). The second control circuit makes use of the temperature measured by the second temperature sensor 152b. This is compared to a second desired temperature set for the second space. The second pump 124b of the second hot water circuit (and of course fan 134) is controlled on the basis of the measured and desired temperature.

In a further embodiment (figure 6) the communication between the second temperature sensor 152b and hot water appliance 100 takes a wireless form, for instance via a Direct WiFi connection. Second housing 150b is provided for this purpose with a WiFi network transmitter/receiver 158b. Hot water appliance 100 is also provided with a WiFi network transmitter/receiver 168. It is hereby not necessary to draw extra cables.

In yet another embodiment (figure 7) a first housing 150a is provided with a control panel 156a. The control panel is connected to a WiFi network transmitter/receiver likewise arranged in first housing 150a. Via this WiFi network transmitter/receiver the control panel communicates with a WiFi network transmitter/receiver 168 in ^' hot water appliance 100. Messages sent from control panel 156a to hot water appliance 100 mainly comprise information about the keys which have been pressed. Messages in the opposite direction mainly comprise information which is shown on the screen associated with control panel 156a. In an embodiment control panel 156a is part of a dedicated operating device (wireless remote control). In an alternative embodiment housing 150a is the housing of a mobile phone which runs a dedicated application in order to communicate with hot water appliance 100 via a Direct WiFi connection.

In another embodiment (figure 8) hot water appliance 100 is provided with a web server 169. The web server has a (wireless or wired) connection to for instance a home network 210 via a network card. A mobile phone or tablet computer 150a (with a keyboard and screen 156a) is provided with a WiFi network chip and communicates wirelessly with home network 210. The address of web server 169 is visited via an internet browser on mobile phone or tablet 150a. The web server presents the user of mobile phone or tablet 150a with a user interface for operating hot water appliance 100. The user is for instance able to change the desired

temperature, modify a program, view the temperature measured (by temperature sensor 152b) , view the temperature variation during the day, view status information of hot water

appliance 100 (for instance number of burning hours per day) and view error messages. If home network 210 allows

connections from the internet it is even possible for a technician to consult web server 169 via the internet using his/her personal computer in order to remedy malfunctions or to for instance perform an online combustion check.

In yet another embodiment (figure 9) the web server on which the user interface can be found is an external server, and control unit 154 communicates with this web server via internet 210. Control unit 154 need then only have an IP address so that it can be accessed via the internet. The functions incorporated in hot water appliance 100 are limited here to the actual control of pump 124 and fan 134. By providing the user interface on an external web server it can be modified in simple manner without operations having to be performed for this purpose on hot water appliance 100. The user interface can thus be improved and added to when new technical options become available. The control unit 154 on hot water appliance 100, which need comprise only the minimum hardware and software to be able to perform the most basic functions, even when the connection to the outside world is lost, can then always be reconfigured when the user interface is modified.

In this embodiment control unit 154 has two operational modes; a first mode in which the control is based on

operating instructions entered via the user interface and transmitted via the internet to input/output unit 155, and a second mode in which the control takes place on the basis of a desired temperature stored in memory 153. This can be a single temperature or a predetermined program of

temperatures at determined times of the day. The first mode is the normal operational mode, while the second mode is an exception mode. This latter mode serves only to guarantee continued operation of hot water appliance 100 in the unlikely event operating device 154 were not to receive any operating instructions, for instance due to failure of the network to which input/output unit 155 is connected. In both modes an actually measured temperature originating from temperature sensor 152 applies as reference. In order to enable realization of both operational modes, the actual control part 157 of control unit 154 comprises two operating programs, which are shown ¹ schematically here; an extensive regular operating program 162 which acts on the basis of the operating instructions coming in via input/output unit 155 and a much more limited emergency program 161 which acts on the basis of the information stored in memory 153.

Figure 10 shows schematically how control unit 154 switches between the two operational modes. After a control cycle has been started in block 201, a check is made in block 202 as to whether input/output unit 155 is receiving signals which may comprise operating instructions.

When this is the case, these instructions are read in block 203 and, among other information, a desired

temperature value T _gew is derived therefrom.. The measured temperature T is subsequently read in block 205. This measured temperature is then compared in block 206 to the desired temperature T _gew . If it follows from this comparison that the desired temperature has been reached, the control unit need not undertake any further control action and the program returns to checking for the presence of input signals in block 202. If on the other hand it follows from the temperature comparison in block 206 that a control action is required, control signals for pump 124 and fan 134 are generated in block 207. The program then returns to block 202.

When it is determined in block 202 that input/output unit 155 is not receiving (or has not received) any

operating instructions, a switch is made to the emergency program. The desired value of the temperature T _gew , which is stored in memory 153, is in that case read in block 204. The program then continues reading the measured temperature in block 205. All further program steps are identical to the steps taken when an input signal is detected.

Optimal use can in this way be made of the

possibilities of the internet or other external sources in order to make available a highly user-friendly operation with extensive options without extensive provision having to be made for this purpose in the hot water appliance.

Furthermore, the operational reliability of the hot water appliance is in this way always guaranteed, even when communication means fail.

The described embodiments and the embodiments shown in the figures are only exemplary embodiments by way of

illustration of the invention. The invention is not limited to these embodiments. It will be apparent to the skilled person that many variations of and modifications to the shown embodiments are possible within the invention. Instead of storing a desired temperature in the memory of the control unit another control parameter could also be stored, for instance a table with switch on/off times. The

input/output unit would then have to receive a time signal instead of a temperature signal. It is thus also possible without problem to combine features of different embodiments to form new embodiments without departing from the

invention. The shown embodiments are therefore not

limitative for the scope of protection sought. The scope of protection is defined solely by the following claims.