A method, a heat measurement device and an installation for distributing heating costs

The invention relates to a method of measuring heat consumption in a room in a building, wherein the measurement comprises measurement of the difference between the temperature of a heat source and the room, respectively.

For many years it has been known to calculate a heat consumption based on the difference in temperature between a heat source and the room temperature.

It is thus well known to calculate the heat emission from a radiator as

Q =Kδtexp.k, wherein K and k are constants. By summation of δt, the heat consumption for a given period of time can be determined.

For instance, German patent publication No. 44 09 185 teaches a heat meter, wherein the mean temperature of the radiator and the mean temperature of the room are used.

It is the object of the invention to provide a method of measuring heat consumption, wherein the heat consumption can be measured accurately over a given period of time and in a manner which is both reliable and inexpensive compared to the prior art.

This object is accomplished in that the time mean temperature is calculated continuously and stored during a predetermined, given period of time, where the heat consumption is calculated as the difference between the time mean temperature of the heat emitter and the time mean temperature of the room temperature.

With reference to the prior art mentioned above, it should be emphasized in this context that the mean temperatures mentioned in the patent disclosure concern the temperature of the place which physically represents an average temperature. For instance, it will be known that the average temperature of a radiator can be measured about 66 % upwards of the radiator, and, correspondingly, experience and standards show how the average temperature of a room is measured. Those values must not be mistaken for the calculation of a mean temperature over time as is the case with the present invention.

According to a preferred embodiment, a heat meter is arranged on a radiator and a heat meter is arranged in the room at a distance from the radiator for measuring the room temperature. These days it is very inexpensive to manufacture electronics for calculating and storing the time mean value, whereby it is possible, eg by means of an electronic reading head, to read the time mean temperature for a certain period of time. By reading the time mean value for a meter on the heat source and a meter for room temperature, measured over identical periods of time, it is possible to find a value for the heat consumption.

Now it is well-known to use several temperature meters to advantage, and they may be connected to each other, either via a wired network or via radio connections. A wired network is expensive to install, and radio connections also increase the cost and simultaneously contribute to increasing the level of the electromagnetic radiation in living quarters. Moreover, it is a well-known problem to have to configure a number of apparatuses to the effect that they are in communication with each other in a building without them interfering with other corresponding apparatuses in the building.

All of the above drawbacks are obviated by storing the time mean temperature for the temperature in a room sensor and in a meter on the radiator, due

there being no need for those two meters to be in communication with each other when the heat calculation is based on the difference between the time mean value of the two meters.

The invention also concerns a heat meter comprising a temperature sensor for providing temperature information and comprising an electronic circuit for processing the temperature information.

The heat meter is characterised in that the circuit comprises a data storage for storing a time mean temperature during a predetermined period of time and comprising means for transferring the time mean temperature to another electronic circuit.

An installation for distributing the costs of heating the individual rooms in a building may comprise two such heat meters, wherein the one heat meter is arranged on a heat source for measuring its time mean temperature, while the other meter is arranged in the room for measuring the time mean temperature of the room.

Preferably the meter for measuring the time mean temperature of the room is arranged at a distance from the meter for measuring the temperature of the heat source, but according to one embodiment an additional room temperature meter may also be provided close to the meter of the temperature of the heat source. A combination of two such meters on the radiator is known from WO 97/22863 and has many advantages, but also the disadvantage that the consumers are able to manipulate the measurement result eg by covering the meter with insulating material, whereby δt between the two meters becomes small. However, by combining this with a particular room sensor, such possible manipulation is eliminated.

It is a further advantage of the plant according to the invention that it becomes possible to present the time mean temperature for the room and the heat source, respectively, to the consumers who are thereby able to continuously monitor their heat consumption, whereas the known summation of δt does not provide the consumers with any useful information. The invention will be explained in further detail by the following description of a number of embodiments, reference being made to the drawings, wherein:

Figure 1 shows a first embodiment of the arrangement according to the in- vention;

Figure 2 shows a block diagram for description of the method according to the invention;

Figure 3 schematically shows the components of an embodiment of a meter according to the invention; while

Figure 4 shows an alternative embodiment of an installation according to the invention.

Figure 1 shows a room in a dwelling house comprising walls, floor and ceiling. In the wall 1 a window 2 is provided and underneath that, a heat source in the form of a radiator 3 is provided. It is noted that the invention is not limited to a particular heat source. For instance, a gas radiator may equally well be employed. It is thus also of absolutely no consequence whether the radiator is heated by means of electricity or a water-borne central heating system.

On the radiator 3 a heat meter 4 is arranged which, in a manner known per se, comprises a sensor being in heat-conducting contact with the radiator and comprising electronic circuits for performing calculations and storage of information from the sensor. Typically, the meter 4 is arranged at a height

corresponding to 66 % of the height of the radiator, experience having shown such arrangement to entail that a temperature is measured which is equal to the mean temperature of the radiator surface. This also means that, in a manner known per se, one is able to calculate the power emitted by the ra- diator as:

Q =Kδtexp.k, wherein K and k are constants,

δt being the difference between the radiator's mean temperature and the room temperature. The temperature of the room varying a few degrees from floor to ceiling depending on the convection, ventilation, etc., it is of some consequence where the room temperature meter is arranged. A typical arrangement is about 1 m above floor and not on exterior walls. For instance, the room sensor may be provided as shown by the room sensor 5 in figure 1.

Figure 2 is a block diagram showing the principle according to the invention. The calculation processes taking place in blocks 6 and7 are performed by the electronic circuits in the meter 4. The calculations in blocks 8 and 9 take place by means of electronic circuits in the room sensor 5, while the calculations appearing from blocks 10 and 11 are typically made elsewhere than in the meters 4 and 5.

By means of the sensor in the meter 4, one is able to measure the mean temperature of the radiator prevailing at any time, ie the current temperature of the radiator measured 66 % upwards thereof, as mentioned earlier. According to the invention, a time mean value is provided of the temperature of the radiator measured for a predetermined period of time. This can be provided eg by instantaneous measurements being performed of the mean temperatures of the radiators once a minute; and by adding all measurements and dividing by the number of minutes elapsed since the starting time, the mean time value of the radiator mean temperature is found. Thus, the time mean value is a calculation value which is, at any time, stored in the meter 4 and which, if desired, can be shown to the consumer.

In the block 8 measurements of the room temperature are performed which can also be done eg once a minute; and by adding the measurements and dividing by the number of minutes elapsed since the starting time, see block 9, the time mean value for the room temperature is found, since τ=0.

Now the heat consumption can be calculated as is shown in blocks 10 and 11. First δt is calculated as the difference between the two time mean temperatures from blocks 7 and 9, it being, of course, important in this context that the values are calculated for a common period of time. The calculation formula will appear from block 11.

The calculations in blocks 10 and 11 can be provided by means of various physical methods.

A first method may consist in one having a separate electronic reading apparatus which - when taken to the vicinity of the meter 4 and/or 5 - is able to receive data wirelessly. Since it is possible hold a reading head close to the meters, the transmission method would typically be by means of infrared light. Instead of a meter reader having previously to read a meter on the radiator, all it takes now is to hold an electronic meter head in proximity of the radiator and room sensors.

Another method consists of providing the meters 4 and 5 with such powerful radio transmitter that they are able to send signals to a central which is common to the entire dwelling house. Thereby the reading procedure is made completely redundant, but in turn the meters become more expensive. For small installations one would prefer to use a reading head which is brought into close proximity of the meters, whereby it is possible to manufacture them at very low costs. It would otherwise be impossible to provide these advan-

tages without calculating the time mean value as it is done in accordance with the invention.

A third method which may be used in very large dwelling houses, where a wired data network is already established, is to make use of such rather than transmitting the temperature information wirelessly.

Figure 3 shows a block diagram for a meter according to the invention for exercising the method explained above in the context of figure 2.

The meter 12 comprises a temperature sensor 13 which is arranged in direct contact with the radiator surface and is configured for emitting a signal to a measurement amplifier 14. At fixed intervals, eg once a minute or every ten minutes, a measurement result from the sensor 13 is added in the block 15, following which, in block 16, a division is performed by the number of time periods elapsed since a predetermined period of time. The result is stored in a storage and can be shown in a display 17 and/or taken to an amplifier 18 which, by means of an antenna or infrared diode 19, is able to emit information about the time mean value stored at any time for the measure tempera- ture. In case the time mean value is shown on a display 17, and this is done both for the radiator temperature and the room temperature, a consumer may himself keep an eye on how the heat bill increases as time goes by.

The embodiment shown in figure 4 of the plant according to the invention comprises, in addition to what was shown and explained in the context of figure 1 , a further room sensor 20. It is known, for instance from WO

97/22863, to use a room sensor arranged on the radiator, but insulated in relation thereto, whereby it is possible to measure the room temperature. In principle, one may omit the room sensor 5, which is shown in both figures 1 and 3, but by using only radiator and room temperature meters that are both arranged on the radiator, the adverse option is open to the consumers that

they may manipulate the measurement. For instance, by covering the room sensor on the radiator by means of a blanket or the like, the room sensor would instead measure a temperature which is approximately like the temperature of the radiator, whereby the δt measured - both instantaneously and as a mean value for a given period of time - would be very small. By supplementing with the room sensor 5 as shown in figure 4, it is possible to also take that kind of problems into consideration, as it will be understood that, according to the invention, the time mean temperature is continuously updated in all meters 4, 5, 20.