GB1571351A

GB1571351A - Regulating device for a hot-water central heating installaation

Info

Publication number: GB1571351A
Application number: GB18952/77A
Authority: GB
Original assignee: Compagnie Electro Mecanique SA; Centre Scientifique et Technique du Batiment CSTB
Current assignee: Compagnie Electro Mecanique SA; Centre Scientifique et Technique du Batiment CSTB
Priority date: 1976-05-07
Filing date: 1977-05-05
Publication date: 1980-07-16
Also published as: FR2350558B1; DE2720526A1; DE2720526B2; DE2720526C3; ES458288A1; SE435961B; SE7705266L; FR2350558A1; IT1077386B

Description

(54) REGULATING DEVICE FOR A HOT-WATER CENTRAL HEATING INSTALLATION (71) We, CEM-COMPAGNIE ELECTRO MECANIQUE, a French Corporate Body, of 12 Rue Portalis, 75008 Paris, France, and CENTRE SCIENTIFIQUE & TECHNIQUE DU BATIMENT, a French Corporate Body of 4 Avenue du Recteur Poincare, Paris 16, France, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - The present invention relates to a regulating device for a central heating system in a building.

It is known to use with a central heating system that includes hot water fed radiators, a device which controls the temperature of the water fed to the radiators as a linear function of the ambient temperature outside the building. However, such a known regulating device provides only a crude control of the heat supply to the building since it does not take account of such factors as the non linear heat emission characteristic of the radiators as a function of the temperature of the heated feed water to the radiators. Moreover, the ambient temperature outside the building is not the only factor which affects heat loss from the building, and sunshine incident on the building frequently produces variations in the internal temperature.

Regulating devices have been proposed which take into account sunshine incident on the building. However the proposed devices are not altogether satisfactory since they do not take into account the total amount of heat supplied to the building by the solar radiation but:merely control the output of the heating system on a continuous basis in dependence upon the incident solar flux at any particular moment in time. It can be shown that since the total solar heat gain is not taken into account by the previously proposed devices, overheating of the building will result with a consequent waste of energy.

In accordance with the present invention there is provided a central heating system in a building, the system having a regulating device which comprises means arranged to sense the ambient temperature outside the building, means arranged to sense solar radiation incident on the building, means for sensing the heat supplied to the building by the central heating system, computing means responsive to the three said sensing means and arranged to provide an output indicative of the instantaneous rate of heat loss or gain of the building, integrating means responsive to the output ofthe computing means and arranged to produce a signal indicative of the total heat loss or gain of the building within a given sample period, and control: means arranged to control the heat supplied to the building by the central heating system as a function of the signal from the intergrating means hereby to tend to maintain an equilibrium between the heat losses and gains of the building.

The invention also includes a method of regulating a central heating system in a building comprising sensing the ambient temperature outside the building, sensing the flux of solar radiation incident on the building, sensing the rate of heat supplied to the building by the heating system, computing from the sensed variables aforesaid the amount of heat loss and/ or gain of the building over a predetermined sample period, and controlling the heat supplied to the building by the heating system in such a manner as to maintain the heat losses of the building equal to the heat gains thereof during a subsequent period.

In one particular form of the invention, the heating system comprises radiators fed with hot water and the regulating device is constituted by an analogue computer which is adapted to draw up continuously an instantaneous thermal balance for the building, that is to say the difference between the heat losses of the building and the heat gain of the building from the heating system and the sunshine. The output of the computer is fed to a store which accumulates the computer output over a given period. At the end of the period, the store is interrogated and the output of the store is used to control a motorised valve which determines the temperature difference between the hot water entering and leaving the radiators.

In order that the invention may be more fully understood and readily carried into effect embodiments thereof will now be described by way of example and by way of contrast with a central heating system which incorporates a prior art regulating device, reference being had to the accompanying drawings in which:: Figure la illustrates a prior art heating system controlled by a regulating device which controls the temperature of water fed to radiators of the system, as a linear function of the outside temperature; Figure lb is a graph of the controlled temperature ofthe water fed to the radiators in Figure 1, as a function of the outside temperature; Figure 2 illustrates schematically a central heating system in accordance with the invention; Figure 3 illustrates in more detail the regulator of the system of Figure 2; Figure 4 illustrates switching apparatus for use in controlling operation of a servo-motor which drives a mixing valve; Figure 5 is a circuit diagram of a modified embodiment of regulating device for use in a system of the invention;; Figure 6a illustrates an arrangement for controlling the servo-motor, which includes a further switch to permit the temperature of the water fed to the radiators to be limited in dependence upon the outside temperature; Figure 6b is a graph illustrating the limiting of temperature of water fed to the radiators by the apparatus of Figure 6a; Figure 7a illustrates an arrangement for controlling the servo-motor, in which the temperature of water returned from the radiators is limited in dependence upon the outside temperature; Figure 7b is a graph illustrating the limiting return water temperature by the apparatus of Figure 7a; Figure 8 is a diagram of a regulating circuit adapted to produce a reduction in the inside temperature of premises during the night.

The notations used in the next and the Figures are the following: a) Temperatures te: instantaneous temperature outside the building td: temperature of the heating water leaving the radiators tr: return temperature of water from the radiators tC: set or desired temperature in the building tB: minimum outside temperature for which the installation has been calculated to operate tDB: temperature of the water fed to the radiators when the outside temperature is equal totg tDC: outgoing temperature of the water for te = tC tRB: return temperature of the water for toe = to tRC: return temperature of the water for te = tC b) Component parts of the heating system Ch: boiler or generator for producing hot water.

V.M.: three-way mixing valve mixing the return water with the water coming from the boiler. It is therefore the device for regulating the heating flow.

S.M.: servo-motor controlling the mixing valve. It has two directions of running designated by "+ heat" and "- heat".

P: circulation pump ensuring the constant flow Q of water in the heating devices.

Rad: radiators or heating devices.

Reg: regulator TD: probe measuring the temperature of the outgoing water.

TR: probe measuring the temperature of the return water TE: probe measuring the outside temperature te TS: probe subject to the influence of the sunshine measuring a temperature ts. The solar radiation is measured by the difference ts-te.

The diagram of Figure la illustrates a central heating system having a conventional regulating device which controls the temperature td of water entering a heating device Rad as a linear function of the ambient temperature te outside the building containing the heating system.

In the system, the boiler Cli is connected to the heating device Rad (which illustrates sche matically all the various radiators etc. in the building) by means of a mixing valve VM and a circulation pump P. The return is effected directly from the heating body Rad to the boiler Ch. Some of the relatively cool return water is taken off and fed into the heated water from the boiler Cli by the mixing valve VM which is adjustable by a servo-motor SM.

The outside temperature te is sensed by a probe TE and the outgoing temperature td of the water is sensed by a probe TD situated at the inlet of the heating device Rad. The two variables te, td are fed into a regulator Reg, which controls the servo-motor SM of the valve VM to mix relatively cool return water from the heating device Rad at a temperature tr, with hot water leaving the boiler Ch, the valve being operated such that the temperature td is controlled as a linear function of The outside temperature te.

Figure 1 b shows the variation in the water temperature td with changes in the outside temperature te between a base temperature tB (Riven) and the set temperature te.

The heating requirements of a building depend on a certain number of climatic parameters, the principal ones of which are the outside ambient temperature, the heating effect of sunshine on the building, and the cooling effect of the wind.

In well-sealed and well insulated buildings, the effect of the wind becomes negligible and only the outside temperature and sunshine have a significant effect on the amount of heat to be supplied by the central heating system.

The heat flow from the building depends upon the following factors.

(a) heat losses due to the difference between the inside temperature and the outside temperature, (b) heating of the building by the sun, (c) heating produced by the central heating system, (d) other internal heating contributions.

The internal contributions provided by heating sources internally of the building, can be compensated for within the building by an auxiliary regulator which controls the heating system in dependence upon the inside temperature. in which case the set temperature tc of the auxiliary regulator is adjusted to a value equal to the inside temperature ti. Alternatively, when the central heating system does not have an auxiliary regulator, the effect of the internal heating contributions can be compensated for by means of the central regulator Reg. If the temperature gain caused by the internal heating contributions is designed by anti, the set temperature tc of the regulator is adjusted such that tc = ti - nti.

It is not always possible to balance instantaneously the heat losses and heat gains of the building, since the solar heat gain may, for example, at certain hours of the day, exceed the losses of the building by a very large amount It is therefore necessary to be able to postpone the balance of the thermal balance in time, and fortunately this can be done without detracting from comfort since, because of the thermal capacity of the building, the variations in the outside temperature, in the sunshine and in the energy supplied by the heating system are not immediately reflected in the inside temperature.

In short, the energy which the heating system should supply is such that over a longer or shorter period of time, depending on the thermal inertia of the building, the following equality is obtained: (heat supplied (Losses of the build- (Solar (by the heat- = (ing due to the diff- -(contri- (ing system (erence between in- (butions (side temperature (and outside tem (perature.

In order to simplify the explanation, hereinafter the case of a building of rectangular shape will be considered, with the sun shining on one of its facades.

For the building considered, as following designations will be used: G: the coefficient of volumetric heat loss in W/m30C Sv: Glazed surface of the facade in m2 V: habitable volume of the building in question in m3 f: solar energy transmission factor of the glazed openings R: solar radiation striking the facade in wlm2 Q: volumetric flow of the water feeding all the heating bodies in m3 Isec.

C: volumetric heat of the water in J/m3 OC.

The solar contributions per unit of habitable volume are equal to: Sv -xR V The contributions due to the heating per unit of habitable volume have the value: Qe V The losses per unit of habitable volume are: G(Tc-te) Thus required balance of heat losses and heat gains of the building can be written as follows:

where z represents time.

Figure 2 illustrates a heating system in accordance with the invention which includes a regulator that calculates the various integrals of equation (1), over a given sample period and calculates from the integrals the net heat loss or gain of the building. The regulator is used to control the heat output to the building from the heating system in such a manner as to tend to maintain the heat losses of the building equal to its heat gains.

The heating system comprises a boiler CH, a heating device Rad ,a mixing valve V.M. with its servomotor SM and a constant flow rate circulation pump P. The servo-motor SM is operated by a regulator Reg.

Now in equation (1) the variables are te, R, (td - tr) and z, and the constants of the equation for the building concerned as are the parameters G, S, and V. The term Q.C. of the equation will also be considered constant since the pump P operates at a constant flow rate.

In the system of Figure 2, the variables te and R are measured by probes Te and Ts respectively, whilst the variable (td - tr) is computed in the regulator Reg from measurements of td and t1 produced by temperature probes TD and TR respectively.

The regulator Reg is preset with the constants of the equation (1) as follows: (a) the flow of the water per volume of Q habitation Q, (b) the coefficient of volumetric Sv loss G, and (c) the ratio f Sv; together with. the set temperature tC.

Figure 3 shows the regulator arrangement of Figure 2 in more detail. The regulator includes an analogue computer 1 connected to a probe TE, the electrical resistance of which varies as a function of the outside temperature, a variable resistance probe Ts responsive to the flux of solar radiation incident on the building, a rheostat Tc enabling a set temperature tc to be preset in the computer, a variable resistance probe TD sensitive to the temperature td of the heating water supplied the heating device Rad, and a variable resistance probe TR sensitive to the return temperature tr of the heating water after its passage through the heating device Rad.

The probes TE and T8 are connected in a resistance bridge which is connected to a comparator t1. The comparator Al provides an output (ts - te) which can be shown to be directly proportional to the solar flux R. The amplifier El has a negative feedback path that includes a potentiometer preset to a value to cause the output of the amplifier to be multi plied plied by a factor f V with respect to the am- V plifier's input.Thus, the output of the amplifier S E1 is proportional toR.f V The temperature probe TE and the rheostat Tc are connected to a comparator A2 which provides an output indicative of (tc - te). The output of the comparator n2 is applied to an amplifier E2 provided with a feedback loop that includes a potentiometer preset to cause the amplifier's output to be multiplied by a factor G with respect to its input. Thus, the output of the amplifier E2 is proportional to G(tc-te).

Similarly, the probes Tr and Td are connected in a bridge to a comparator A3 which provides an output proportional to (tr - td), which is multiplied by a factor QVC by means of an operational amplifier E3 provided with a preset potentiometer in a negative feedback loop. Thus, the output of the amplifier E3 is proportional to - Q.C. (td - tr).

V The outputs of the amplifiers E1, lye2, E3 are summed by a inverting summing amplifier z and the resulting sum is applied to an integrator 2 connected to a store 3. The store 3 is interrogated by means of pulses from a pulse generator 4 and the interrogated output from the store 3 operates a relay which controls a switch C1. Another switch C2 is provided which is operated by another relay in response to a pulse train from the pulse generator 4.

The switches C1, C2 are connected in series and control the timing and the direction of running of the servo motor SM which operates the mixing valve V.M that controls the temp era- ture of the water reaching the heating devices Rad.

The regulator thus operates as follows.

Depending on the sensed values of the variables te, R, td and tr, and the preset parameters G, Tc, f Sv, Q, the analogue computer 1 com V V' putes an instantaneous power balance (i.e. the instantaneous heat loss or gain for the building) and provides from the summing amplifier a voltage A 0 proportional to this balance, i.e.

The integrator 2 integrates the instantaneous power balance and the result of the integration is accumulated in the store 3 to derive an integrated power balance:

The store 3 is interrogated periodically (for example every five minutes) by means of the generator 4. The state of the store at the moment of interrogation represents the thermal energy balance of the building i.e. the net heat gain or loss between successive interrogations.

In certain cases, it may only be required to knov whether the heat provided by the central heating system is more than (0 is then < 0) or less than ( is than > 0) that required, in which case only the sign of 0 need be detected from the store 3. In other arrangements it may be necessary to know the precise value of 0 . Alternatively, it may be required to know whether 0 is outside or inside a dead region defined by two values, + z and -: such an arrangement has the advantage that the capacity of the store 3 can be kept within reasonable bounds. Thus, for example, in the case of a stoppage of the heating of the building for ten days, it would be unrealistic to say that the energy for which the heating system should compensate immediat ely on restarting should correspond to the integral of the losses G(tc - te) accumulaXed during the ten previous days. Actually, in this case, the fixed set temperature tC (tc = 200C, for example) no longer represents the actual inside temperature ti. After the stoppage of the heating, this latter temperature will tend to become equal to the outside temperature at the end of a certain time, depending on the cooling time constant of the premises.

In practice, the integral A dz has two limits, which may or may not be symmetrical about zero, the one corresponding, for example, to the integral of the losses during a temporary reduction in the heating (priority given to the production of service hot water by stopping the heating, stoppage of the heating during part of the night, etc.), and the other corresponding, for example, to the integral of the solar contributions which the building can effectively recoup wituout detracting from comfort.

Depending on the information collected regarding the state of the store, the regulator acts on the device for regulating the heating flow A T in such a manner as to cancel the integral = i A dz dz as quickly as possible.

In the example given, the regulator acts on the mixing valve by controlling the servo-motor step-by-step in the direction of " + heat" when > 0 and in the direction of "- heat" when < O.

Figure 4 illustrates the control circuit for the servo-motor. The switch contact C1 which defines the direction of rotation of the servomotor SM is in the position "+ heat" when the sign of the integral A dz is positive and in the position " - heat" when the sign of the preceding integral is negative. The contact C2 determines the duration of running Z1 of the servo-motor within the period Z0 which is the interval of time separating two successive interrogations of the store. The ratio 1 is fixed in zo the example described and is defined by the duration of pulses from the pulse generator 4.

The ratio could however be made subject to the absolute value of the integral A |t dz, if it were desired that the speed of action of the servo-motor should increase with the amplitude of the lack of balance of the balance.

The heat balance expressed as

requires four constants to be preset in the computer 1 (tc, G, QC , and fSv ) which complicates the operation of the system when it is first installed, particularly as the parameters G and Q are often not well known in the existing buildings.

By dividing by G, the previous relationship becomes

with Kr = and Ks = f Sv Kr=-andKs GV GV Now parameter Kr can be expressed as tC tB Kr = te - tB A t nominal tc designating the set temperature tg the base outside temperature for which the installation is calculated, and At nominal is the drop in temperature of the water circulating in the heating bodies during continuous operation, when the outside temperature is equal to the calculated base temperature. These values are known with much more precision than the values of G and of Q.

Since the parameter Kr is a significant factor in the heat balance equation, it is important to be able to indicate it with the maximum of precision.

As for the parameter Ks which represents the compensation for the solar heating contributions, it is of less importance. It is naturally relatively less precise because of the coefficient f (solar transmission factor of the glazed opening). The errors made in the estimation of the coefficient G are therefore of less importance in the calculation of Ks than in the calculation of Kr. Hence, it is advantageous to be able to determine K1 by the indirect method described above.

A block diagram of a regulator is indicated in Figure 5, which is very similar to that described with reference to Figure 3. In Figure 5, the amplifiers E', and E'3 correspond to the amplifiers El and E3 of Figure 3. The coefficients applied to the signals leaving the comparators A1 and A3 are however Ks and Kr respectively. Since these coefficients Kr, K5 are obtained by dividing the coefficients applied to the amplifiers E1, E2, E3 by the factor G, the requirement for the amplifier E2,which would then have the coefficient 1, is eliminated.

It is sometimes necessary to limit the temperature td of water leaving the valve VM, to remain below a certain threshold, for example in order to avoid the problems of noise due to too rapid and too frequent variations in the temperature of the water feeding the heating device Rad. Now, in operation of regulators previously described, nothing limits the temperature td apart from the thermostat of the boiler Ch.

However, it. is possible to effect cancellation of the heat losses and gains to the building whilst maintaining the temperature td below a certain fixed or variable threshold value; and Figure 6a illustrates a control arrangement for the servomotor SM which permits the temperature to be limited below a threshold depending on the outside temperature te, as shown by the straight line A in the graph of Figure 6b.

The control arrangement for the servo-motor SM includes a change-over contact L. This contact is in the position 1, 2 so long as the temperature td, for an outside temperature te, is situated below the straight line A. This is normal operation. However, when the temperature td rises above the straight line A, the contact L cuts the circuit 1, 2 and establishes the connection 1, 3, thus operating the servo-motor to cause the temperature td to be reduced.

It is also possible to control the temperature tr within certain limits which has particular application to central heating systems which utilise geothermally heated water. In geothermal heating, it is essential to work with as high a temperature difference as possible between the extracted and the returned geothermally heated water. Since the temperature of the extracted water is constant, the temperature of the water before its return must be monitored and Figure 7a illustrates an arrangement for controlling operation of the servo-motor S.M.

such that the temperature is held below a presselected threshold. The contact L establishes the connection 1, 2 so long as the return temperature tr is situated below the line B shown in Figure 7b for a given outside temperature te (normal operation).

When the temperature tr is above the line B, the contact L breaks the connection 1, 2 and establishes the connection 1, 3, to drive the servo-motor S.M. to deliver cooler water to the heating devices Rad.

An official requirement in France is that maximum mean temperature of premises used for habitation must not exceed 20"C. However, in the existing buildings with a high proportion of glazed surface, a day-time temperature of 21"C is often necessary. On the other hand, during the night, the users prefer lower temperatures. The system should therefor lower the night temperature and be able to increase the temperature by day, while ensuring that over a whole day (24 hours), the mean inside temperature does not exceed 20"C.

A conventional regulating device, without a store, does not allow this mean temperature to be controlled strictly. More or less complex and more or less precise solutions have been devised to try to solve the problem. The solution must frequently used in the past is the following: The regulation comprises three heating cycles.

1) a normal temperature operation from 0800 hours to 2300 hours.

2) a lower temperature operation from 2300 hours to 0600 hours.

3) An accelerated operation from 0600 to 0800 hours.

The lowering of the set point of the regulation is of the order of 3 to 50C during cycle 2).

Despite this lowering, the heating continues and the energy transmitted to the heating bodies is proportional to the difference between the lower temperature and the outside temperature. The consequence of this is that the temperature in the building at night does not actually drop to the set lower temperature nor does it reach the temperature that would be obtained by the natural cooling down of the accommodation when the heating is stopped.

The users therefore tend to open the windows of the rooms to benefit from fresher air. Hence over-consumption of energy arises. Moreover, this has been confirmed by various studies carried out in situ, in the course of which it was found that the consumption in relation to the difference between inside temperature and outside temperature increased at night by nearly 10%.

The duration of cycle 3 is adjusted ac cording to the professional activities of the occupants e.g. the time they get up to have breakfast. The object of this accelerated operation is to try to compensate for the partial lack of supply of energy during the night to bring the inside temperature back to that required for cycle 1 . Unfortunately, this compensation is far from accurate because the prior art heating systems do not evaluate the total reduction of energy supplied during the night in cycles); nor do they calculate the excess power supplied during the whole period of accelerated operation.

However, with heating system according to the invention, it is possible to stop the heating from 2300 hours to 0600 hours, for example, This enables a greater drop in inside temperature to be obtained. Moreover, as a result of the storage of the balance 01, the system will remember, on starting up at 0600 hours, the lack of supply of energy during the night. It will first of all make up for this by using all the available power and then, when balance has again been reached, i.e. when 0 tends to zero,the system will operate to tend to minimise 9 as previously described.

Nevertheless, when the days are very cold, a stoppage of the heating from 2300 hours to 0600 hours risks being too long for the heating system to be able to make up entirely for the losses. It is therefore desirable to be able to reduce the period of interruption in the heating.The diagram or Figure 8 illustrates a system which enables this to be done.

The contacts of the type C1 (1C1, 2C1), C2 and L work in an identical manner to those of Figure 6. In particular, the contact 2C1 only closes (establishing the connection 7, 8) when the cumulated balance is zero or negative (heating in advance of needs). A contact H (clock contact) closes between 2300 hours and 0600 hours. A relay C3 iS provided, controlling contacts 1 C3 and 2C3. In order that the relay, may be energized, such that the contact 2C3 cuts the connection 4, 5 to establish the connection 4, 6 and cause the servo-motor to rotate in the direction - heat", until the heating of the premises is stopped, two conditions are necessary: 1) that the clock contact H must be closed (in the example 2300 hours to 0600 hours); and 2) the contact 2C1 should be closed, that is to say that the heating should be in advance of the needs.

It is only if these two conditions are fulfilled that it will be possible to stop the heating during the night. The contact 1C3 is a selfholding contact eliminating the influence of the contact 2C1 when the relay C3 has been operated.

Of course, it would not be departing from the scope of the invention, if instead of stopping the heating for part of the night, the set temperature was merely reduced. In this case there would be two settings: a a setting designated by Tcj defining the mean temperature of the premises over a whole day (24 hours); the losses of the building would then always be evaluated in relation to this set temperature.

a a setting designated by TCN defining the maximum energy which the heating system would supply during the period that the set temperature is reduced.

WHAT WE CLAIM IS: 1. A central heating system in a building, the system having a regulating device which comprises means arranged to sense the ambient temperature outside the building, means arranged to sense solar radiation incident on the building, means for sensing the heat supplied to the building by the central heating system, computing means responsive to the three said sensing means and arranged to provide an output indicative of the instantaneous rate of heat loss or gain of the building, integrating means responsive to the output of the computing means and arranged to produce a signal indicative of the total heat loss or gain of the building within a given sample period, and control means arranged to control the heat supplied to the building by the central heating system as a function of the signal from the integrating means whereby to tend to maintain an equilibrium between the heat losses and gains of the building.

2. A system in accordance with claim 1 wherein the building includes a plurality of radiators adapted to be fed with hot water, and wherein the means for sensing the heat supplied to the building by the system comprises temperature sensors arranged to sense the temperature of water respectively entering and leaving the radiators.

3. A system in accordance with claim 2 wherein the control means includes a motorised valve driven in response to the value of the said signal from the integrating means, said valve being arranged to mix selectively relatively cold water returned from the radiators with relatively hot water fed to the radiators.

4. A system in accordance with claim 2 or 3 wherein the integrating means includes a store for accumulating the output of the computing means during said sample period, and means for interrogating the store at the end of the sample period.

5. A system in accordance with claim 4 wherein the interrogating means determines the sign of the information in the store, and wherein the control means is arranged to drive the motorised valve for a predetermined period in a direction dependent upon said sign.

6. A system in accordance with claim 4 wherein the interrogating means determines both the sign and magnitude of the informa tion in the store, and wherein the control means is arranged to drive the valve for a time dependent upon said magnitude and in a direction dependent upon said sign.

7. A system in accordance with any one of claims 2 to 6 and including means for main taining the temperature of the water supplied to the radiators below a threshold temperature, the threshold temperature being a linear function of the temperature outside the build ing.

8. A system in accordance with any one of claims 2 to 6 and including means for maintaining the temperature of water leaving the radiators below a threshold temperature which is a linear function of the temperature outside the building.

9. A system in accordance with any of claims 2 to 8 including a solar temperature sensor arranged to produce a signal having a magnitude dependent upon the flux of solar energy incident on the building, a first comparator for comparing the output of the sensing means that senses said outside temperature with the output of the solar temperature whereby to provide a first comparison signal indicative of the magnitude of the solar flux incident upon the building, means for establishing a signal indicative of a desired temperature within the building, a second comparator arranged to compare said desired temperature signal with said outside temperature signal whereby to derive a second comparison signal, and a third comparator arranged to compare the outputs of the sensors which sense the temperature of water entering and leaving said radiators whereby to derive a third comparison signal, means for multiplying at least two of said comparison signals by factors dependent upon the amount of glazing and the thermal conductivity characteristics of the building, and summing means arranged to sum the comparison signals in such a manner as to provide said output indicative of the heat loss or gain of the building.

10. A central heating system incorporating a regulating device substantially as herein described with reference to Figures 2 to 7 of the accompanying drawings.

11. A method of regulating a central heating system in a building, comprising sensing the flux of solar radiation incident on the building, sensing the rate of heat supplied to the building by the heating system, computing from the sensed variables aforesaid the amount of heat loss or gain of the building over a predetermined sample period, and controlling the heat supplied to the building by the heating

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. during the night. The contact 1C3 is a selfholding contact eliminating the influence of the contact 2C1 when the relay C3 has been operated. Of course, it would not be departing from the scope of the invention, if instead of stopping the heating for part of the night, the set temperature was merely reduced. In this case there would be two settings: a a setting designated by Tcj defining the mean temperature of the premises over a whole day (24 hours); the losses of the building would then always be evaluated in relation to this set temperature. a a setting designated by TCN defining the maximum energy which the heating system would supply during the period that the set temperature is reduced. WHAT WE CLAIM IS:

1. A central heating system in a building, the system having a regulating device which comprises means arranged to sense the ambient temperature outside the building, means arranged to sense solar radiation incident on the building, means for sensing the heat supplied to the building by the central heating system, computing means responsive to the three said sensing means and arranged to provide an output indicative of the instantaneous rate of heat loss or gain of the building, integrating means responsive to the output of the computing means and arranged to produce a signal indicative of the total heat loss or gain of the building within a given sample period, and control means arranged to control the heat supplied to the building by the central heating system as a function of the signal from the integrating means whereby to tend to maintain an equilibrium between the heat losses and gains of the building.

system in such a manner as to maintain the heat losses of the building equal to the heat gains thereof during a subsequent period.

12. A method of regulating a central heating system substantially as herein described with reference to Figures 2 to 7 of the accompanying drawings.