WO2008039065A1

WO2008039065A1 - Device, system and method for controlling a heating system

Info

Publication number: WO2008039065A1
Application number: PCT/NL2007/000247
Authority: WO
Inventors: Erwin Johannes Maria Waalders
Original assignee: Kamstrup B.V.
Priority date: 2006-09-29
Filing date: 2007-10-01
Publication date: 2008-04-03
Also published as: NL1032598A1; NL1032598C2

Abstract

The present invention provides a device for controlling a heating system for heating one or more rooms in a building, the control device comprising a heat meter of the invoicing type which is connectable to the feed conduit and/or return conduit and which is adapted to determine the power of the fluid sent through the conduit and to generate an indication of the heat supplied over a determined period, and a control unit which can be connected to the fluid flow adjusting unit and which is adapted to control the power of the fluid passing through the fluid flow adjusting unit, wherein the control unit is connected to the heat meter and is adapted to control the fluid flow adjusting unit subject to the power determined by the heat meter.

Description

DEVICE , SYSTEM AND METHOD FOR CONTROLLING A HEATING SYSTEM

The present invention relates to a device and a method for controlling a heating system for heating one or more rooms in a building, wherein the heating system comprises a feed conduit for feeding warm fluid, a 5 return conduit for discharging cooled fluid, one or more heating elements, such as radiators and/or floor heating conduits, to be disposed in the rooms and connected to the feed and return conduits, and a fluid flow adjusting unit for adjusting the flow rate of the warm fluid

10 flowing to the heating elements. The invention also relates to such a heating system.

Existing central heating apparatus and district heating networks usually have a central room thermostat which is disposed in one of the rooms and with which the

15 desired temperature can be set in the relevant room of the building. The thermostat measures the air temperature in the room and sends a signal to a control unit of the heating apparatus, which control unit then actuates the heating apparatus. Depending on the set

20 temperature, the heating apparatus sends more or less heat into the feed conduit .

Such an actuation of the heating apparatus takes place on the basis of the temperature of the warm water feed, and optionally on the basis of the temperature of

25 the water discharge. The temperature of the warm water feed and of the water discharge is measured using temperature sensors provided in the respective conduits.

A drawback of the known feed temperature-dependent control of the heating apparatus is that the method of

30 heating the room leaves something to be desired. In many cases an 'overshoot' will for instance occur, meaning that following actuation of the heating apparatus a higher temperature is reached at a given moment than has been set (the overshoot) , so that the heating apparatus is down-regulated or switched off. After a time the room temperature once again falls too low, which means that the heating apparatus is adjusted upward or switched on again. Constantly switching the heating apparatus on and off usually causes an unstable room temperature. This all means that the desired room temperature set via the room thermostat is not realized in energetically optimum manner, and this results in an unnecessary loss of heat. A further drawback is that the comfort of those present in the room is limited, since at one moment they will be too cold and the next moment too warm as a result of the fluctuations in the room temperature.

It is noted that a system is known from DE-A- 3.505.082 in which use is made of a plurality of valves but in which regulation takes place not on the basis of power but on the basis of at least pressure, and possibly also temperature, for which purpose diverse - if not excessively many - pressure sensors and also temperature sensors are provided. That regulation is possible on the basis of power is not known herefrom. Controllable valves of the type which can be either opened or closed are also used which have little flexibility and which in any case cannot bring about a satisfactory regulation, in particular a limiting. Furthermore, the only disclosure in this document is that a recording of consumed power must take place to enable billing of the consumer or user for this consumption. There is no indication whatever in this document that the control takes place on the basis of a desired power to be supplied or of any regulation to satisfy this demand other than a simple limiting. It is an object of the present invention to provide a device, system and method in which at least one of the above stated drawbacks is obviated.

It is also an object of the present invention to provide a device, system and method in which relatively little energy is used and in which increased comfort can be realized for those present in a building.

According to a first aspect of the present invention, there is provided for this purpose a device of the above stated type, comprising:

- a heat meter connectable to the feed conduit and/or return conduit; and

- a control unit which can be connected to the fluid flow adjusting unit and which is adapted to control the power of the fluid passing through the fluid flow adjusting unit; wherein the control unit is connected to the heat meter and is adapted to control the fluid flow adjusting unit subject to the power determined by the heat meter. Because use is made of the power of the fluid flowing through the feed conduit and determined by the heat meter, reaching of the desired temperature in the different rooms can be brought about in improved manner by actuating the fluid flow adjusting unit. Surprisingly, the power produced by the heating system is a better measure of the heating process occurring in the relevant room than the temperature of the feed and the discharge.

When the heating system is for instance connected to district heating, the fluid is supplied - at a temperature which cannot be influenced by the user but which sometimes changes - via the feed conduit. By increasing or decreasing the flow rate of the fluid flowing through the feed conduit using the fluid flow adjusting unit, which comprises for instance a control valve or the like, the correct amount of heat can be supplied to the heating elements so as to reach the desired room temperature. In most cases a heat meter of the invoicing type is already present in such a heating system. The heat meter is therefore preferably a heat meter of the invoicing type which is adapted to determine the power of the fluid sent through the conduit and to generate an indication of the heat supplied over a determined period. Such heat meters are used to determine the heat consumed by a user in a determined period and to debit this to the energy supplier. These heat meters are generally quite accurate, so that the amount of heat consumed can be determined with a small margin of error. By making use of the heat meter of the invoicing type which is already present, or which is at any rate not yet present but is required, in determining the power through the feed conduit, an additional heat meter for driving the heating system can be omitted, this bringing about a considerable simplification, and an associated cost- saving, of the control device.

According to a preferred embodiment of the invention, the heat meter is provided with a display screen with which the heat supplied in said period (i.e. the heat supplied by the heat source minus the heat fed back to the heat source) can be indicated to enable invoicing of the heat provided by the energy supplier. Instead of a display screen, or in addition thereto, the heat meter can be provided with an optionally wireless communication unit, so that the heat generated in said period, in addition to possible further quantities such as temperature of the water supply and water discharge, can be readily inspected by the user and/or the supplier using a receiver, for instance a computer provided with a receiver. According to a further preferred embodiment, the heat meter is adapted to determine the power in the feed conduit and the power in the return conduit . The delivered power can be determined more accurately by measuring both the power in the feed conduit and the power in the return conduit .

According to a further preferred embodiment, the heat meter comprises:

- a flow meter for determining the fluid flow rate in the feed conduit;

- a temperature sensor for determining the temperature of the fluid in the feed conduit; and

- a computing unit for computing the power through the conduit on the basis of the determined temperature and the determined flow rate.

The flow meter which determines the fluid flow rate consists in an advantageous embodiment of a velocity meter for measuring the velocity of the fluid flowing in the conduit. The flow rate of the fluid in the conduit can be derived directly on the basis of the velocity and the pre-known cross-section of the conduit. The computing unit can easily determine the power through the relevant conduit on the basis of the thus derived fluid flow rate and the temperature of the fluid. In the case that the power in both the feed conduit and the return conduit must be determined, temperature sensors are arranged in both the feed conduit and the return conduit and it is possible to suffice with a single flow meter, either in the return conduit or in the feed conduit since, at least when there is no leakage, the flow rate on the feed side is the same as the flow rate on the discharge side. This means a further simplification of the control device.

In a particularly advantageous embodiment the heat meter and the control unit are integrated so that a highly compact and operationally reliable driving of the heating system can be effected. The heat meter and control unit can for instance be arranged in a shared housing, wherein the control unit is embodied in a particularly advantageous embodiment as a plug-in of the heat meter. This makes retrofitting of the control unit in an existing heat meter extremely simple.

According to a further preferred embodiment, the device comprises a shared power supply for the heat meter and the control unit. The power supply can be provided by the domestic mains supply, by a battery or by a combination of the two. In most cases the control unit will however be powered using the domestic mains supply, so that the battery power supply normally present in the heat meter can be omitted. This makes the control device not only simpler and cheaper in construction, but also eliminates the necessity of replacing batteries after a period of time.

By making use of the existing heat meters which, for invoicing purposes, comprise components of high accuracy, the power can be determined with the accuracy of ± 1.5% or better, preferably even ± 0.5% or better. At this high accuracy a number of advantageous methods of driving the heating system has become possible, as will become apparent below. In practice the computation of the power is carried out in less than about four seconds and the total number of computations per hour amounts to more than about 650. By determining the power at said speed an adequate driving of the heating system on the basis of power can be realized.

According to a further preferred embodiment, the control device comprises an air temperature sensor for measuring the temperature of the ambient air in a room, wherein the air temperature sensor is in communication connection with the control unit for the purpose of controlling the fluid flow adjusting unit subject to both the measured air temperature and the measured power. The control device controls the flow rate of the warm fluid via the feed conduit using an open or closed, relatively slow control loop on the basis of the room temperature and using a second control loop on the basis of the determined power. The second control loop is relatively fast (in other words has a relatively small time constant) . The heating and cooling of a room progresses slowly. The heat content of a building, dwelling and objects therein is in other words large in relation to the power of the heating elements. Temporary disruptions such as incident solar radiation, opened doors and windows, change in the number of people present in the room and switching on heat-producing appliances also generate temperature changes which progress relatively slowly. In contrast, the power measurement and regulation has a small time constant since the power is measured in the relatively fast- flowing fluid.

According to a further embodiment, the control unit comprises a receiver for wireless reception of commands from a displaceable remote control . The remote control is preferably embodied such that it can also be carried by a user. Using the remote control a user can for instance increase or decrease the temperature in one or more of the rooms in the building as desired, without the control device itself, or a fixed manual operating means for the control device coupled thereto, here having to be operated. In a further preferred embodiment the operating unit comprises not only a receiver but also a transmitter (for instance an integrated transmitter/ receiver) so that the operating unit can also send information to the remote control, such as for instance information concerning the status of the heat source, the temperature of the feed water, the temperature of the return water and so on. This information can for instance be displayed on a screen provided on the remote control . In a particularly advantageous embodiment the above- mentioned air temperature sensor is provided in the remote control . When the user carries the remote control, each room in which the user is located at that moment will be set automatically to the desired comfortable temperature using the remote control.

According to another aspect of the invention, there is provided a heating system for heating one or more rooms in a building, comprising:

- a feed conduit for feeding relatively warm fluid from an external heating source;

- a return conduit for discharging relatively cold fluid;

- at least one heating element, such as a radiator and/or a floor heating conduit, to be disposed in a room;

- a fluid flow adjusting unit connected to the feed conduit for adjusting the flow rate of the fluid flowing into the feed conduit ;

- a heat meter connected to the feed conduit and/or to the return conduit; and

- a control unit which is connected to the fluid flow adjusting unit and which is adapted to control the power of the fluid passing through the fluid flow adjusting unit; wherein the control unit is also connected to the heat meter and the control unit is adapted to control the fluid flow adjusting unit subject to the power determined by the heat meter.

According to a further preferred embodiment, the system comprises a circulation pump with adjustable pump flow rate connected to a conduit, wherein the pump flow rate can be controlled by the control unit subject to the power determined by the heat meter.

In a preferred embodiment the heating system comprises a floor heating system. In this embodiment the fluid flow adjusting unit comprises a control valve in addition to a circulation pump with adjustable pump flow rate, wherein the pump flow rate can be controlled by the control unit subject to the power determined by the heat meter. When for instance in the case of floor heating the supplied power is insufficient in particular circumstances, for instance when the heat supply from the heat source is insufficient, a circulation pump is necessary to obtain extra heat from the heat source. When the heat demand is small the pump can be stopped

(the pump then allows flow through the rotor but adds no pump power) , as the demand increases the circulation pump is switched on, wherein the flow rate is increased one step at a time with increasing pumping capacity. As the heat demand decreases, the capacity of the pump can be reduced. If the power (heat) which the system must supply is known, as is the case according to the invention, it is also known how fast (i.e. at what pumping capacity) the circulation pump must operate. In floor heating systems the circulation pump necessary for floor heating normally operates continuously, which is unnecessary and expensive. The power regulation according to the invention makes it possible to control the pump capacity as required and even to stop the pump if it is not required for circulation. By controlling the control device and the circulation pump in different capacity steps instead of only on the basis of ^λ on/off less electricity is used to control the circulation pump, and a lower return temperature results. The heating system is otherwise of a type in practice wherein the user has no influence on the temperature of the supplied fluid, as can be the case in an individual central heating installation. The heating system is for instance a district heating system, wherein the heat is supplied externally, i.e. feed water and return water conduits are realized from the public highway. The heating system can also be a floor heating system, wherein the heat is generated either in the dwelling itself by burning for instance natural gas in a central heating boiler, or is supplied via the above- mentioned district heating system. Finally, the heating system may be a group heating system, wherein the heat comes from outside the dwelling but from within the same building. This is for instance the case in an apartment complex in which different apartments have one shared heating boiler, a heat pump installation or mini-CHP installation, optionally in combination with a warm tap water supply. According to another aspect of the invention, there is provided a method for heating one or more rooms in a building with a heating system comprising at least one feed conduit and at least one return conduit, a fluid flow adjusting unit for adjusting the flow rate of the fluid flowing into the feed conduit, and a heat meter for measuring power of the fluid flow in the feed conduit, the method comprising the steps of:

- connecting a control unit to the heat meter;

- determining with the heat meter the power of the fluid flowing through the feed conduit;

- controlling the fluid flow adjusting unit with the control unit subject to the determined power for the purpose of adjusting the power of the fluid passing through the fluid flow adjusting unit. The heat meter is preferably an existing heat meter of the invoicing type, so that no additional heat meter need be provided and the control device can therefore be arranged simply and at relatively low cost . In a further preferred embodiment, particularly (though not exclusively) in the case of floor heating, the method comprises of the control unit reducing the feed temperature for a determined time interval, for instance the night period, and increasing the feed temperature at the end of said time interval subject to the length of the time interval and the energy level, determined from the measured power, of the fluid passing through the fluid flow adjusting unit.

Further advantages, features and details of the present invention will be elucidated on the basis of the following description of several preferred embodiments thereof. Reference is made in the description to the figures, wherein figures 1-5 show schematic views of respective preferred embodiments of a heating system and control according to the invention.

Figure 1 shows schematically a floor heating system 1. Via an external heat source, such as a district heating network or a central heating (CH) installation, warm water is supplied in a feed flow (direction P₁) via a warm water feed pipe 2. The supplied warm water is guided via a control valve distributor 32 (in the shown embodiment a three-way valve) and a circulation pump 9 through a number of conduits 10, 11, 12 (direction P₂) arranged in the floor of the rooms in a building. The warm water runs through conduits 10-12 and relinquishes heat to the floor in which the conduits are arranged. A number of conduits 10-12 are herein placed in or on the concrete floor or the channels arranged for this purpose. A part of the water of the return flow, which has in the meantime at least partially cooled, is discharged (direction P₃) via a cooled water discharge pipe 3, and another part of the return flow is mixed with the supply flow (direction P₄) via the control valve distributor 32. A heat meter 14 is provided in the warm water supply- pipe 2 of heating system 1, or is at least connected thereto. Heat meter 14 comprises a (schematically shown) velocity meter 15 arranged in pipe 2. Velocity meter 15 can be of a type in which the liquid water sets a rotor into rotation, and this rotation is measured and thereby ^■ provides a measure for the velocity of the liquid in feed conduit 2. The rotation speed is measured with a speed measuring element (not shown) connected to a microcontroller 19. On the basis of the measured rotation speed and a value for the cross-section of feed pipe 2 pre-stored on microcontroller 19 the microcontroller computes the momentary flow rate (volume per unit time) of the liquid flowing in pipe 2.

Other methods of determining the velocity of the liquid in feed pipe 2 are also possible. It is for instance possible to envisage a measurement with ultrasound or a magnetic-inductive measuring method.

Heat meter 14 is further connected to a (schematically shown) temperature sensor 20 likewise arranged in feed pipe 2. Temperature sensor 20 generates a signal which is representative of the temperature of the liquid in feed pipe 2. Temperature sensor 20 is connected to microcontroller 19. On the basis of the temperature signal from temperature sensor 20 and the velocity signal from the speed measuring element the microcontroller 19 can therefore determine the momentary flow rate and the associated temperature of the liquid flowing in the pipe. On the basis of the flow rate and the temperature the microcontroller 19 computes the momentary power (energy per time unit) flowing into floor heating system 1 via warm water feed pipe 2. In another embodiment shown in broken lines in figure 1, heat meter 14 also comprises a second temperature sensor 22 which is placed in return pipe 3. In similar manner to the first temperature sensor 20, second temperature sensor 22 is connected to microcontroller 19 and provides microcontroller 19 with a signal representative of the momentary temperature of the water in discharge pipe 3. If it is assumed that there is no loss of water in the conduit system, the flow rate of the water supplied in feed pipe 2 is the same under stationary conditions as the flow rate of the cooled water in return pipe 3, so that a separate flow rate meter in return pipe 3 can be omitted. The two power associated with supplied water and the power associated with cooled water are subtracted from each other in this embodiment in order to compute the supplied heat. Heat meter 14 is also provided with an LCD screen 23 on which can be read in known manner, among other information, the momentarily supplied power, the (accumulated) power supplied over a determined time interval, the feed water temperature, the discharge water temperature, the temperature difference, the water flow speed, the momentary flow rate in the water feed pipe and so forth. Heat meter 14 is suitable for invoicing purposes, which is understood to mean that for the supplier of the warm water it keeps track of how much heat is supplied to a user and the cost which can be billed for this supply. Such heat meters 14 are often, though not always, already present in district heating networks (systems with individual warm tap water as well as collective warm tap water (IWT/CWT) and in apartments with a shared CH apparatus) . Heat meter 14 is coupled to a connection terminal 29 of a control unit 26, for instance via a connecting line 25 or using a wireless connection (not shown) . Control unit 26 is assembled from a microcontroller 27, a number of memories 28, a connection terminal 29 for connection to heat meter 14, an input terminal 30 for connection to the thermostat 34 to be described below, and an output terminal 31 for connection to a control valve mechanism 32 provided in feed pipe 2. Control valve mechanism 32 is arranged in feed pipe 2 and can adjust the flow rate of the liquid flowing in feed pipe 2 in stepped manner or in continuously variable manner. Such control valves are generally known and a detailed description thereof is therefore omitted here. The control valve can also be arranged in return pipe 3 instead of in feed pipe 2. The function of the control valve does not hereby change, although this can be recommended because the average temperature of the return water is lower than that of the supplied water. Also placed in feed pipe 7 of the floor heating system is a temperature sensor 8 with which the temperature of water sent into the floor heating conduits can be determined. In similar manner to the first temperature sensor 20, temperature sensor 8 is connected to microcontroller 19 or microcontroller 27, and provides to microcontroller 19, 27 a signal representative of the momentary temperature of the water in pipe 7.

Microcontroller 27 of control unit 26 receives via input terminal 29 a signal from heat meter 14 which is representative of the power being delivered at that moment to the heating system. Microcontroller 27 likewise receives a signal from thermostat 34 via input terminal 30. Thermostat 34 is arranged in a random room, usually for instance the living room, of a dwelling, and comprises a temperature setting button 40 with which the user can set a desired temperature (T₁) . Thermostat 34 also comprises a temperature sensor 41 with which the temperature (Tj of the ambient air of thermostat 34 can be measured. This temperature is representative of the temperature in the relevant room. When there is a difference between the temperature (Tj measured by- sensor 41 and the set temperature (T₁) , thermostat 34 generates a signal representative of this difference to input terminal 30 of control unit 26. On the basis of this signal and on the basis of the signal at input terminal 29 thereof, this signal being representative of the power determined at that moment, microcontroller 27 of control unit 26 computes how the set temperature (T₁) can be reached, as optimally as possible energetically and with maximum comfort for the users, by adjusting the flow rate through feed pipe 2. Once control unit 26 has determined which flow rate is at that moment desirable, it sends a signal via output terminal 31 to control valve mechanism 32 which places the control valve in the desired position. In the shown embodiments the circulation pump 9 is also actuated by control unit 26. With a correct adjustment of the quantity of warm water supplied from feed conduit 2 and a correct mixing with the cooled water from the return conduit, the three-way valve of valve mechanism 32 substantially provides in this embodiment for the temperature of the water flowing through the floor heating conduits, while circulation pump 9 substantially provides for the flow rate of the water. In other embodiments, such as for instance shown in figures 4 and 5, the control unit controls only the control valve mechanism, as will be set forth below.

As is apparent from the foregoing, control unit 26 therefore determines the desired flow rate through feed pipe 7 on the basis of the power of the water being supplied at that moment as well as the air temperature of the room to be heated or made cooler. An extremely- efficient driving of the heating system can be realized through the direct link between the current air temperature, the desired temperature and the momentary power.

In the embodiment of heating system 1 shown in figure 1 the heat meter 14, control unit 26 and control valve mechanism 32 are shown as separate components. It is however recommended to integrate the heat meter and the control unit to form an integrated unit 17, for instance by arranging thereof in a shared housing 18 as shown in figure 2. This can result in space and cost- savings . Figures 1 and 2 show that the power supply 35 for heat meter 14, control valve mechanism 32 and control unit 26 is shared and is provided from the domestic mains supply (H) . This means that batteries or accumulators present in many cases in a heat meter 14 can be dispensed with, this achieving a further simplification of the system.

Figure 3 shows the situation in which the above- mentioned thermostat 34 is replaced by a portable thermostat 36. Portable thermostat 36 is also provided with a setting button 40 and temperature sensor 41. The connection between portable thermostat 36 and control unit 26 preferably takes place via a wireless connection (Infrared, WiFi and so on) so that thermostat 36 can be readily placed at the desired positions in the rooms. Portable thermostat 36 can be placed in one of a number of holders 37a-37d mounted on the wall in four different rooms. Thermostat 36 can also be carried by the user in order to modify settings.

The best-known standard heating systems consist of one or more heating elements for each room for heating, such as for instance radiators, which are provided with a thermostat, in addition to one central thermostat usually placed in the living room. The central thermostat determines the temperature in the living room, while the other thermostats regulate the temperature in the other rooms. The drawback hereof is that the temperature in the other rooms will normally vary more than in the living room. This is in some cases not the optimum situation. If however use is made of portable thermostat 36, which is carried by the user or arranged in a holder 37 in one of the rooms, it is possible to ensure that the system remains optimized at all times for that room where the temperature must be most accurately controlled. This does not of course necessarily have to be the living room.

Shown in the figures with a broken line is that control unit 26 can also be connected to circulation pump 9. Control unit 26 can hereby drive the circulation pump at distinct capacity levels, as stated above. Figure 4 shows the situation where heating takes place with a number of radiators 50, 50', 50''. The operation of the embodiment shown in figure 4 largely corresponds with that of the embodiment shown in figure 1, and a lengthy description thereof can therefore be dispensed with. Note that there is no feedback of the return flow to the feed flow. All liquid which has passed through the radiators is discharged via return conduit 3. This means that the control valve mechanism can be given a simpler form, for instance in the form of an adjustable two-way valve 32'. Radiators 50,50',5O¹' are provided with respective thermostatic valves 52, 52 ', 52" .

In figure 5 is described an embodiment which has an operation corresponding for the greater part with that of the embodiment shown in figure 1. An extensive description thereof can therefore be dispensed with. In this embodiment the central thermostat 34,36 is omitted and the temperature in the rooms is adjusted by operating the thermostatic radiator valves 52, 52 ' , 52 ' ' in combination with a clock program in the control device for off-peak hours reduction.

The control device according to the invention further has a number of other advantages not mentioned above. A heating installation consisting of a district heating unit and radiators must for instance be set hydraulically. The radiators are provided for this purpose with setting valves 51,51',5I¹'. These setting valves are given a certain adjustment during said setting. The setting valves must not be confused with the (thermostatic) radiator valves operated by the resident . Because the regulation according to the invention makes use of a heat meter with which, among other things, the flow is accurately measured, this measurement can be used in the hydraulic setting of the heating installation. Setting takes place as follows. The radiators are closed except for the radiator to be set. The radiator valve is fully opened and the setting valve is adjusted so that the flow through feed pipe 2 (which flow is accurately measured) acquires the desired value.

In the heat distributing units currently available on the market from suppliers the regulation takes place on the basis of input parameters such as hydraulic pressure difference and/or water temperatures and/or room temperature. The regulation according to the invention makes use of rapid and precise measurements of the quantities of feed and return temperature of the water, the flow rate, the power and, for the more refined variant of the regulation, also the prevailing and desired room temperature. The regulation according to the present invention is hereby better able than the currently available regulating means to respond adequately to changes in the setting of radiator valves. These changes are detected immediately and the regulation can also respond immediately.

Because the power delivered is measured precisely with a heat meter, it is likewise possible to precisely regulate the power which is delivered. The power of a unit can also be limited very easily due to this accurate measurement.

Another form of limiting is the limiting of the flow through the unit, with the object of limiting the flow through the radiators as a comfort-enhancing measure (less noise) . By making use of the flow data from the heat meter, for instance data relating to the flow rate through the feed conduit computed by means of the velocity meter, the maximum flow speed through the radiators can be determined and adjusted quite precisely. Another advantage of the regulation according to the invention is that the so-called off-peak hours reduction (which is frequently applied to a relatively rapid room heating system with radiators) can likewise be applied to floor heating systems. These latter systems are considerably slower than systems with radiators, whereby the floor heating is usually left on at night.

The regulation according to the invention is better than the control systems applied heretofore and in many cases brings off-peak hours reduction within reach in the case of floor heating. In the heat meter the supplied energy is determined by integration in time. This is used, depending on the number of hours that there is no heating and depending on the difference between desired and actual room temperature, to employ a higher feed temperature than is normally permitted in respect of the safety margins which must be observed (the floor may for instance not become too hot, etc.) . The higher temperature is maintained until there is the danger of exceeding an energy level to be more definitely determined. This increases the possibilities of off-peak hours reduction in floor heating which, despite the temporarily higher feed temperature, can be energy-saving .

Although this is not described directly in the foregoing, the warm tap water supply in most cases forms an integral part of the heating system according to the invention. There are basically two types of warm tap water supply. One is Individual Warm Tap water (IWT) wherein cold tap water is heated using for instance a plate exchanger. The other is Central Warm Tap water (CWT) wherein the consumed warm tap water is for instance measured by a warm water meter.

The present invention is not limited to the preferred embodiments thereof described herein. The rights sought are rather defined by the following claims, within the scope of which many variants can be envisaged.

Claims

1. Control device for a heating system for heating one or more rooms in a building, wherein the heating system comprises a feed conduit for feeding warm fluid, a return conduit for discharging cooled fluid, one or more heating elements, such as radiators and/or floor heating conduits, to be disposed in the rooms and connected to the feed and return conduits, and a fluid flow adjusting unit for adjusting the flow rate of the warm fluid flowing to the heating elements, which control device comprises :

- a heat meter connectable to the feed conduit and/or return conduit; and - a control unit which can be connected to the fluid flow adjusting unit and which is adapted to control the power of the fluid passing through the fluid flow adjusting unit; wherein the control unit is connected to the heat meter and is adapted to control the fluid flow adjusting unit subject to the power determined by the heat meter.

2. Device as claimed in claim 1, wherein the heat meter is of the invoicing type and is adapted to determine the power of the fluid sent through the conduit and to generate an indication of the heat supplied over a determined period.

3. Device as claimed in claim 1, wherein the heat meter is provided with a display screen with which the heat supplied in said period can be indicated to enable invoicing of the supplied heat.

4. Device as claimed in any of the foregoing claims, wherein the heat meter is adapted to determine the power in the feed conduit and the power in the return conduit .

5. Device as claimed in any of the foregoing claims, wherein the heat meter comprises: - a flow meter for determining the fluid flow rate in the feed conduit;

- a temperature sensor for determining the temperature of the fluid in the feed conduit; and - a computing unit for computing the power through the conduit on the basis of the determined temperature and the determined flow rate.

6. Device as claimed in any of the foregoing claims, wherein the heat meter and control unit are integrated.

7. Device as claimed in claim 6, wherein the heat meter and control unit are arranged in a shared housing.

8. Device as claimed in claim 6 or 7, wherein the control unit is embodied as a plug-in of the heat meter.

9. Device as claimed in any of the foregoing claims, comprising a shared power supply for the heat meter and the control unit .

10. Device as claimed in any of the foregoing claims, wherein the heat meter is adapted to determine the power with an accuracy of ± 1.5% or better, preferably ± 0.5% and better.

11. Device as claimed in any of the foregoing claims, comprising an air temperature sensor for measuring the temperature of the ambient air in a room, wherein the air temperature sensor is in communication connection with the control unit for the purpose of controlling the fluid flow adjusting unit subject to both the measured air temperature and the measured power .

12. Device as claimed in claim 11, wherein the regulation on the basis of temperature has a greater time constant than the regulation on the basis of power.

13. Device as claimed in any of the foregoing claims, wherein the fluid flow adjusting unit forms part of a heat distributing unit .

14. Device as claimed in any of the foregoing claims, wherein the control unit comprises a receiver for wireless reception of commands from a displaceable, preferably portable remote control .

15. Device as claimed in claims 11 and 14, wherein the air temperature sensor is provided in the remote control .

16. Heating system for heating one or more rooms in a building, comprising: - a feed conduit for feeding relatively warm fluid from an external heating source;

- a return conduit for discharging relatively cold fluid;

- a fluid flow adjusting unit connected to the feed conduit for adjusting the flow rate of the fluid flowing into the feed conduit ; - a heat meter connected to the feed conduit and/or to the return conduit;

- a control unit which is connected to the fluid flow adjusting unit and which is adapted to control the power of the fluid passing through the fluid flow adjusting unit; wherein the control unit is also connected to the heat meter, and the control unit is adapted to control the fluid flow adjusting unit subject to the power determined by the heat meter.

17. System as claimed in claim 16, wherein the heat meter is of the invoicing type and is adapted to determine the power of the fluid sent through the conduit and to generate an indication of the heat supplied over a determined period.

18. System as claimed in any of the foregoing claims, wherein the fluid flow adjusting unit comprises a control valve.

19. System as claimed in claim 18, wherein the fluid flow adjusting unit also comprises a circulation pump with adjustable pump flow rate, wherein the pump flow rate can be controlled by the control unit subject to the power determined by the heat meter.

20. System as claimed in any of the claims 16-19, wherein the heating system is a district heating system.

21. System as claimed in any of the claims 16-20, wherein the heating system is a floor heating system.

22. System as claimed in claim 21, wherein the fluid flow adjusting unit comprises a controllable three-way control valve for adjusting the temperature of the fluid to be sent to the heating elements and a controllable circulation pump for adjusting the flow rate of the fluid to be sent to the heating elements.

23. System as claimed in any of the claims 16-22, wherein the heating system is a shared central heating system.

24. System as claimed in claim 16, provided with a device according to any of the claims 1-15.

25. Method for heating one or more rooms in a building with a heating system comprising at least one feed conduit and at least one return conduit, a fluid flow adjusting unit for adjusting the flow rate of the fluid flowing into the feed conduit, and a heat meter for measuring power of the fluid flow in the feed conduit, the method comprising the steps of:

- connecting a control unit to the heat meter;

- controlling the fluid flow adjusting unit with the control unit subject to the determined power for the purpose of adjusting the power of the fluid passing through the fluid flow adjusting unit.

26. Method as claimed in claim 25, wherein the heat meter is an existing heat meter of the invoicing type.

27. Method as claimed in claim 25 or 26, comprising of measuring the air temperature in one or more of the rooms with an air temperature sensor, sending a signal representative^' of the measured air temperature to the control unit and controlling the fluid flow adjusting unit on the basis of the measured air temperature, the desired air temperature and the measured power.

28. Method as claimed in any of the claims 25-27, comprising of the control unit reducing the feed temperature for a determined time interval, for instance the night period, and increasing the feed temperature at the end of said time interval subject to the length of the time interval and the energy level, determined from the measured power, of the fluid passing through the fluid flow adjusting unit.

29. Method as claimed in claim 28, comprising of controlling a three-way control valve of the fluid flow adjusting unit for the purpose of adjusting the temperature of the fluid sent to the heating elements and controlling a circulation pump of the fluid flow adjusting unit for the purpose of adjusting the flow rate of the fluid sent to the heating elements.