Method of controlling a storage water heater

Abstract

Method for controlling a heating device which may be installed and implemented by a storage water heater (1), said storage water heater (1) comprising at least one heating device, at least one storage tank (10) in which the water is stored and heated, at least one control and management unit capable of controlling at least said at least one heating device, at least one inlet duct (11) through which water may be fed into said tank (10), at least one outlet duct (12) through which water may be sent / withdrawn from the said tank (10). Said method monitors the thermal conditions of the storage by acquiring at least: - a main temperature (Tmain), representative of the general thermal state of the water stored in said tank (10), - an auxiliary temperature (Taux), representative of the thermal state of the water in a zone of the said tank (10) wherein there is the mains water makeup. Said method provides for at least: - checking whether said heating device is switched on, first step (S1); - if the first step (S1) gives a negative result, a second step (S3) is carried out which checks whether said auxiliary temperature (Taux) is lower than or equal to a comfort temperature; - if said second step (S3) gives a negative result, a third step (S30) is carried out which checks whether said main temperature (Tmain) is lower than or equal to a switching on temperature (Tstart) of the said heating device, which may be set by the manufacturer and / or installer and / or user.

Description

[0001] METHOD FOR CONTROLLING A STORAGE WATER HEATER

[0002] DESCRIPTION

[0003] The object of the present invention is a method for controlling a storage water heater, in particular the heating device thereof.

[0004] More in detail, the present invention relates to a method for controlling the activation / deactivation of a storage water heater according to the temperature control of the water of a storage tank.

[0005] In some specific embodiments, the present invention relates to a method for controlling the activation / deactivation of the compressor of a heat pump storage water heater according to the temperature control of the water of a storage tank. As it is known, various types of water heaters exist which may be used to produce hot water for the indoor heating or as sanitary water.

[0006] Such devices may use different types of heat generators, including, for example, immersed electric resistances, in the so-called traditional electric water heaters, heat pumps using a refrigerating cycle to transfer heat from an external source to the water to be heated, or solar energy, gas, geothermal, or similar systems; as well as hybrid or combined configurations between two or more of such technologies. The components and operation of the heat pump water heaters are now standardised and well-known to the man skilled in the art and shall not be described or explored here.

[0007] It is specified that the thermodynamic cycle of the heat pump absorbs heat from the air and transfers it, via phase transitions and compression / expansion cycles ofthe refrigerating fluid, to the water to be heated, thereby bringing the later to a temperature suitable for hygienic-sanitary or indoor heating uses.

[0008] Among the various types of water heaters mentioned above, one of the major drawbacks is the frequency with which the heating device or generator is switched on and off over a given period of time.

[0009] Such phenomenon is known as cycling and consists of repeated and consecutive, therefore systematic, switching on and off of the heating device which leads to: - excessive wear of the mechanical and / or electric components involved in the switching on / off cycles, and

[0010] - increased consumption, since the heating device is switched on even when not strictly necessary.

[0011] In the heat pump water heaters, cycling has particularly negative effects, as it: - causes accelerated wear of the compressor and the control components, due to the continuous mechanical and electrical stresses associated with the frequent starts;

[0012] - reduces the efficiency of the system, as short cycles prevent the optimal operating conditions from being achieved and result in greater energy consumption.

[0013] Currently, in order to address such drawback, it is known to use a hysteresis that, appropriately combined with / subtracted from a threshold temperature value considered as the reference for switching the heat pump on / off, aims to reduce such phenomenon.

[0014] The hysteresis is therefore used to prevent frequent and consecutive restarts of the heating device, especially with heat pump, and is generally set by the manufacturer and / or installer according to the type of water heater and / or the type and configuration of the system, or the like.

[0015] However, once set, the hysteresis does not allow for taking into account the conditions of the water in the storage.

[0016] The use of the hysteresis, even if it is capable of limiting the cycling phenomenon, makes the water heater less ready / responsive to the variations in theoperating / thermal conditions of the storage.

[0017] In essence, the water heater has limited flexibility in adapting to a change in the operating conditions of the water in the storage, conditions that may vary, for example, as a result of a withdrawal.

[0018] Hereinafter, the term “operating conditions” refers to the thermal or temperature conditions of a given portion of the storage or the storage itself.

[0019] The object of the present invention is to obviate such type of drawbacks, by providing for a method of controlling the activation / deactivation of a storage water heater capable of preventing the cycling phenomenon even under variable operating conditions and by limiting the effects on user comfort.

[0020] A further object of the present invention, at least for one or more embodiments, is to provide a method for controlling the activation / deactivation of a storage water heater capable of ensuring a prompt response of the water heater to changes in its operating conditions.

[0021] A further object of the present invention, at least for one or more embodiments, is to provide a method for controlling the activation / deactivation of a storage water heater that is simple to implement.

[0022] This and other objects, which shall appear clear hereinafter, are achieved with a method for controlling the activation / deactivation of a storage water heater or the like, according to claim 1.

[0023] Other objects may also be achieved by means of the additional features of the dependent claims.

[0024] More precisely, these and other purposes are achieved with a method for controlling a heating device which may be installed and implemented by a storage water heater, said storage water heater comprising at least one heating device, at least one storage tank wherein water is stored and heated, at least one control and management unit capable of controlling at least said at least one heating device, at least one inlet duct through which water may be fed into said tank, at least one outlet duct through which water may be sent / withdrawn from said tank, said inlet and outlet ducts being in fluid communication with said tank.The method for monitoring the thermal conditions of the storage comprises acquiring at least:

[0025] - a main temperature, representative of the general thermal state of the water stored in said tank,

[0026] - an auxiliary temperature, representative of the thermal state of the water in a zone of said tank wherein water from the mains is refilled.

[0027] The method, having acquired at least said main and auxiliary temperatures, proceeding at least to the following execution steps:

[0028] - first step: checking whether said heating device is switched on;

[0029] - second step: if the verification of said first step gives a negative result, verifying whether said auxiliary temperature is less than or equal to a comfort temperature which may be set by the manufacturer and / or installer and / or user; - third step: if the verification of said second step gives a negative result, verifying whether said main temperature is less than or equal to an activation temperature of said heating device, which may be set by the manufacturer and / or installer and / or user;

[0030] where, if said third step gives a positive result, switching on said heating device. Further features of the present invention shall be better highlighted by the following description of a preferred embodiment, according to the patent claims and illustrated, purely by way of a non-limiting example, in the accompanying drawing tables, wherein:

[0031] - Figure 1 shows a schematic section view of a first possible executive embodiment of the water heater according to the present invention, where said water heater is equipped with at least two temperature sensors;

[0032] - Figure 2 schematically shows the activation / deactivation of a storage water heater based on to the trends of the main temperature Tmain and of the auxiliary temperature Taux of the storage according to a first possible embodiment of the method for controlling the activation / deactivation of a storage water heater according to the present invention;

[0033] - Figure 3 shows a block diagram of said first possible embodiment of themethod for controlling the activation / deactivation of a storage water heater according to the present invention;

[0034] - Figure 4 shows a block diagram of a further possible embodiment of the method for controlling the activation / deactivation of a storage water heater according to the present invention.

[0035] The features of the method for controlling the activation / deactivation of a storage water heater or the like according to the present invention shall hereinafter be described using the references contained in the figures.

[0036] It should be noted that any dimensional and spatial term (such as “lower”, “upper”, “inner”, “outer”, “front”, “rear”, “vertical”, “horizontal” and the like) possibly used below refers, unless otherwise indicated, to the position according to which the object of the invention shown in the drawings is arranged in operating conditions.

[0037] The parameters and the respective references used hereinafter in the description are listed below:

[0038] - 31: temperature of the water of the storage in the upper half thereof, preferably in proximity to the top zone of the tank, more preferably that substantially adjacent or close to the upper cap (or dome) of the tank;

[0039] - 32: temperature of the water in the lower half of the storage, preferably in proximity to the lower zone of the tank, more preferably that substantially adjacent to the lower cap of the same tank, or that in proximity to the inlet zone of the water refilling;

[0040] - Tavg: average temperature of the water of the storage and may be calculated as: Tavg=a*91 + b* 2. where “a” and “Z>” act as weights in order to carry out a weighted average and which may depend, for example, on the capacity of the tank and / or the extent of the withdrawal and / or on the reactivity and readiness degree that it is desired to be given to the water heater;

[0041] - Tset: set-point temperature, preferably consisting of a temperature at which the storage may be heated / maintained and which may be set by the manufacturer and / or installer and / or user;- Thyst: is a hysteresis value and may be used to avoid frequent and subsequent restarts of the main heating device; it is generally set by the manufacturer and / or installer according to the type of water heater and / or the type and shape of the system or the like; according to the invention it may vary between 1CH-2O°C, preferably between 12-H5°C;

[0042] - Thystl: is an additional hysteresis value and may be used to avoid frequent and subsequent restarts of the main heating device and possible excessive / anomalous overheating of the water heater; it is generally set by the manufacturer and / or installer according to the type of water heater and / or the type and shape of the system or the like; according to the invention it may vary between 2^-5°C, preferably between 2.5- °C;

[0043] - Tmain: main temperature used as a reference parameter for thermostating the water storage, it may be detected by a single temperature sensor, for example positioned in a median or upper zone of the tank, or calculated as a weighted average of the values detected by at least two temperature sensors placed at different heights within the tank, in such case being able to be Tmain=Tavg. In essence, the main temperature Tmain is a parameter representative of the general thermal state of the water of the storage;

[0044] - Tstart: start or restart temperature of the water of the storage at which the heating device is started and restarted, which may be set by the manufacturer and / or installer and / or user, preferably Tstart Tset-Thysl:

[0045] - Tstart! : additional start and restart temperature of the water of the storage at which the heating device is started or restarted, which may be set by the manufacturer and / or installer and / or user, preferably Tstart2 Tset-Thyst2 - Taux: auxiliary temperature, used as an auxiliary parameter to refine the control of the heating device and implement the pre-check step, it is representative of the thermal state of the water of the storage in a zone of the tank wherein the refill of water from the mains takes place and may consist of 92;

[0046] - Tcomf: comfort temperature of the storage, preferably consisting of atemperature which may be set by the manufacturer and / or installer and / or user below which the water of the storage may not be supplied or below which the auxiliary temperature Taux or temperature 92 may not drop; generally, the comfort temperature Tcomf is less than or equal to the start temperature Tstart. Generally, it should be noted that in the block diagrams of Figures 3 and 4, the rectangle shape represents an action, for example the activation of the heating device, while the diamond shape represents a control, for example a comparison among temperatures.

[0047] The term storage water heater is herein to be understood as any device capable of heating water in a storage tank, in particular sanitary hot water for hygienic uses, until reaching a given temperature herein defined as set -point temperature Tset. The term thermostating is herein to be understood as the comparison between the set-point temperature and the temperature of the storage, said comparison being used for controlling the heating device and maintaining the storage substantially at the set-point temperature.

[0048] As clearly shown in the accompanying figures, 1 indicates, as a whole, the storage water heater 1 according to the present invention, hereinafter referred to as only water heater 1, for clarity of description.

[0049] Generally, said water heater 1 may comprise at least one heating device, at least one storage tank 10 wherein water is stored and heated, at least one control and management unit capable of controlling at least said at least one heating device, at least one inlet duct 11 through which water may be fed into the tank 10, at least one outlet duct 12 through which water may be sent / withdrawn from the tank 10, said inlet 11 and outlet 12 ducts being in fluid communication with said tank 10. The heating device may be of the electric type, i.e. comprising at least one electrical device, such as for example electric resistances or the like, or of the heat pump, solar energy, or gas, geothermal type or the like, or possible combinations thereof.

[0050] Generally, in a storage water heater the water inside the storage tank has a stratification according to the temperature, said stratification being due to theheating process caused by the heating elements and the density of the water. In fact, the hottest water tends to migrate and settle in the top part of the tank, while the colder water tends to settle in the lower part of the same tank.

[0051] According to a preferred embodiment, the outlet section 110 of the inlet duct 11 is preferably positioned in the lower half of the tank 10.

[0052] More preferably, the outlet section 110 of the inlet duct 11 is positioned in proximity to the lower zone of the said tank 10.

[0053] According to a preferred embodiment, the inlet section 120 of the outlet duct 12 is preferably positioned in the upper half of the tank 10 or in proximity to the median zone of the tank 10.

[0054] More preferably, the inlet section 120 of the outlet duct 12 is positioned in proximity to the top zone of the said tank 10.

[0055] During the operation of the water heater 1, such arrangement determines a water refill, generally from the mains water at the aqueduct temperature, in the lower zone of the tank 10 and a withdrawal of hot water in the upper zone thereof, thus keeping the stratification of the water according to the temperature thereof and essentially guaranteeing the withdrawal and supply of hot water.

[0056] In the embodiment shown in figure 1, the inlet duct 11 and the outlet duct 12 are inserted from below into the tank 10, passing through the bottom thereof and extending, preferably substantially vertical within the tank 10, reaching different heights.

[0057] In alternative embodiments not shown, the inlet duct 11 and the outlet duct 12 may be inserted into the tank 10 in different positions, for example from the top, passing through an upper wall of the tank 10 and extending preferably substantially vertical; or laterally, through a side wall of the tank 10 and extending preferably substantially horizontal; or according to mixed configurations, wherein the inlet 11 and outlet 12 ducts are inserted on different sides of the tank 10. According to a preferred embodiment, shown by way of a non-limiting example, said heating device comprises a heat pump 2 provided with at least one compressor 22, one evaporator 21, one lamination member and one condenser 20 suitablyarranged so as to heat the water of the storage, for example, according to a possible executive embodiment, said condenser 20 may be arranged in contact with / around the walls of the tank 10 so as to be able to cooperate therewith, at least thermally, and heat the water contained in the same tank 10.

[0058] The water heater 1 may further comprise at least:

[0059] - at least one first temperature sensor 61 capable of detecting the temperature & 1 of the water of the storage, said first sensor 61 being therefore positioned in a hot zone of the same storage; and

[0060] - at least one second temperature sensor 62 capable of detecting the auxiliary temperature Taux or the temperature 92 of the water of the storage, said second sensor 62 being therefore positioned in a cold zone of the same storage or in a zone of the tank wherein the make-up water is fed.

[0061] Preferably, said sensors are suitably connected to and communicating with said control unit, capable of acquiring and / or processing the detections taken.

[0062] Preferably, the second temperature sensor 62 is positioned closer to the water make-up zone than the first temperature sensor 61.

[0063] Preferably, said at least one first temperature sensor 61 is arranged in the upper half of the tank 10, more preferably in proximity to the top zone of the tank 10. Preferably, said at least one second temperature sensor 62 is arranged in the lower half of the tank 10, more preferably in proximity to the lower zone of the tank 10. Said water heater 1 is characterised in that it implements, via the control unit thereof, the control method according to the present invention.

[0064] The method for controlling the activation / deactivation of a storage water heater or the like according to the present invention, provides for managing and controlling the at least one heating device of the water heater 1 so as to reduce the cycling phenomenon and at the same time keep the water heater ready and responsive in responding to a variation of the operating conditions of the storage, for example as a result of one or more withdrawals.

[0065] According to the invention, in order to reduce / eliminate the cycling phenomenon, high hysteresis values Thyst are used, comprised between 1CH-2O°C, preferablybetween 12- 5°C, contrary to what is provided for in the state of the art, which generally provides for values comprised between 3^-5°C.

[0066] The method according to the present invention is characterised in that it comprises a step, herein referred to as pre-check, which takes into account the operating conditions of the bottom part of the storage, i.e., the auxiliary temperature Taux, preferably consisting of / represented by 92.

[0067] As shall be seen below, with the heating device switched off, said pre-check takes priority, over the possible switching on of the same heating device, with respect to the control of the main temperature Tmain of the storage, preferably consisting of / represented by the average temperature Tavg of the storage.

[0068] Essentially, to activate said heating device, the method according to the present invention, prior to checking the operating conditions of the storage (thermostating), provides for carrying out a preliminary check focused on determining the operating conditions of the lower portion of the storage.

[0069] In fact, the control / monitoring of the auxiliary temperature Taux allows assessing / understanding whether a withdrawal is in progress or has just concluded. In fact, considering that the make-up water is preferably fed into the lower part of the tank, so as to preserve the stratification of the water of the storage, the water settling in such lower part shall mix with the make-up water, suddenly cooling itself (it is clear that the extent of such cooling also depends on the amount of make-up water).

[0070] The pre-check, therefore, allows assessing the operating conditions of the lower portion of the storage to determine whether it is too cold and therefore it is necessary to switch on the heating device in order to avoid possible discomfort situations for the user.

[0071] In fact, if, as provided for the state-of-the-art, the activation of the heating device were dependent solely on the control of the average temperature of the storage, in case of a withdrawal the cooling of the lower portion of the storage, following the reintegration of water from the mains, would not be promptly detected.

[0072] In such case, the delay in switching on the heating device would result in anexcessive cooling, at least of the lower portion of the storage, generating discomfort for the user.

[0073] In essence, the method according to the present invention provides for monitoring the thermal conditions of the storage by acquiring at least:

[0074] - a main temperature Tmain, representative of the general thermal state of the water stored in the tank 10, said main temperature Tmain being able to be detected via at least one temperature sensor or calculated as a weighted average of the values detected by at least two sensors placed at different heights inside tank 10, in such case being able to be Tmain=Tavg;

[0075] - an auxiliary temperature Taux, representative of the thermal state of the water in a zone of the tank 10 wherein there is the make-up of mains water, said auxiliary temperature Taux preferably being able to consist of 92;

[0076] so as to check both the general conditions of the storage and the conditions of the lower portion of the storage and evaluate the switching on / off of the heating device.

[0077] In essence, the method according to the present invention, having acquired at least said main Tmain and auxiliary Taux temperatures, provides at least for:

[0078] - checking whether the heating device is switched on, first step SI;

[0079] - if the check of said first step SI gives a negative result, a second step S3 is carried out adapted to check whether the auxiliary temperature Taux is less than or equal to the comfort temperature Tcomf;

[0080] - if the check of the second step S3 gives a negative result, a third step S30 is carried out adapted to check whether the main temperature Tmain is less than or equal to a switching on temperature Tstart.

[0081] Without any limiting intent, the control method of a water heater 1 the heating device whereof is a heat pump shall be described herein.

[0082] With reference to Figures 2 and 3, a first possible executive embodiment of the control method according to the present invention shall now be described, by way of a non-limiting example, which may be preferably implemented via the control unit with which said water heater 1 is provided.Generally, said control unit is therefore capable of controlling and commanding the different components of the water heater 1, such as for example the heating devices provided for.

[0083] To implement such control, the control method may consider different factors, such as for example the set-point temperature Tset, the comfort temperature Tcomf, the auxiliary temperature Taux, and the main temperature Tmain of the water of the storage possibly represented by one or more of the temperatures & 1 and 92 and / or Tavg.

[0084] It should be noted that, in general, the temperature of the water of the storage may decrease due to:

[0085] - at least a make-up of the mains water in response to at least one withdrawal of hot water by the user, as represented by the interval B of Figure 2; and / or - by the heat dispersions through the walls of the tank, as represented by the interval A of Figure 2.

[0086] The control method provides for at least a first step SI, which has the purpose of checking whether the heating device, for example the heat pump 2, is switched on or off.

[0087] In the positive / affirmative case, i.e., if the heating device is switched on, the comparison of the main temperature Tmain with the set -point temperature, Tset, step S2, is carried out, where:

[0088] - if the main temperature Tmain is less than Tset, the heating device remains switched on and the previous said first step2 SI is resumed, to reiterate said comparison;

[0089] - if the main temperature Tmain is greater than or equal to Tset, the heating device is switched off or placed in stand-by (HP=OFF), step S20.

[0090] In the negative case, i.e., if the heating device is switched off, a second step, S3, herein referred to as pre-check step or pre-check S3 is carried out.

[0091] The pre-check S3 provides for comparing the auxiliary temperature Taux with the comfort temperature Tcomf, where:

[0092] - if the auxiliary temperature Taux is less than or equal to the comforttemperature Tcomf, i.e., if said pre-check S3 gives a positive result, the heating device is immediately activated / switched on, step S31;

[0093] - if the auxiliary temperature Taux is greater than the comfort temperature Tcomf, i.e., if said pre-check S3 gives a negative result, the heating device remains switched off or in standby (HP=OFF) and a subsequent third step, S30, is carried out.

[0094] The third step, S30, herein also referred to as control step or check S30, implements the normal thermostating of the storage and provides for comparing the main temperature Tmain with the switching on temperature Tstart.

[0095] According to a preferred embodiment, the switching on temperature Tstart may correspond to the set-point temperature Tset, preferably to the set-point temperature Tset to which a suitably selected / set hysteresis parameter Thyst, is subtracted in order to reduce / avoid frequent and successive restarts of the heating device, where:

[0096] - if the main temperature Tmain is less than or equal to Tstart (Tset-Thyst), i.e., if said third step S30 gives a positive result, the heating device is activated / switched on (HP=ON), so as to bring the temperature of the storage back to the desired and set temperature Tset, step S31;

[0097] - if the main temperature Tmain is greater than Tstart (Tset-Thyst), i.e., if said third step S30 gives a negative result, the heating device remains switched off or in standby (HP=OFF), and the first step SI is resumed.

[0098] In general, in presence of one or more withdrawals, the average temperature of the storage tends to decrease more slowly than the temperature of the lower portion thereof, which decreases much more quickly as it receives and mixes with the make-up water.

[0099] As partially anticipated, the solutions of the state-of-the-art provide for activating the heating device by controlling the average temperature alone, i.e., in such solutions, the switching on of the heating device is dependent on the comparison between the average temperature of the storage and Tset-Thyst (thermostating). In general, considering that here “restart time” refers to the time between aswitching off of the heating device and the subsequent restart thereof, it may be seen that:

[0100] - with low hysteresis values (3^-5), the water heater is more responsive and has shorter restart times, maintaining average temperatures of the storage closer to the set-point temperature value Tset set, during the restart time, while

[0101] - with high hysteresis values (for example, greater than 10) the water heater is less responsive and has longer restart times, with consequent average temperatures of the storage, during the restart time, that are further from the set-point temperature value Tset set and lower than those guaranteed by low hysteresis.

[0102] With these premises, if the state-of-the-art solutions used high hysteresis values (greater than 10) so as to counteract the cycling, the heating device would be switched on after a withdrawal with a longer restart time.

[0103] During said period, the lower portion of the storage, as well as the same storage, may cool down too much, risking to lower excessively the temperature of the water of the storage that may be supplied for the possible withdrawals immediately subsequent to the first, resulting in user discomfort.

[0104] For such reason, therefore, the state-of-the-art adopts low hysteresis values; the purpose is to switch on the heating device earlier than adopting high hysteresis values so as to avoid possible discomforts.

[0105] However, low hysteresis valuespartially solve, either with less effectiveness or not at all, the cycling problem.

[0106] The method according to the present invention provides for:

[0107] - high hysteresis values Thyst so as to effectively counteract the cycling phenomenon (Thyst>10);

[0108] - a pre-check step that allows for monitoring of the operating conditions of the lower portion of the storage, guaranteeing a prompt response of the water heater as such operating conditions vary, particularly in case of one or more withdrawals.

[0109] In accordance with the method according to the present invention:- when there is no withdrawal request, the pre-check S3 on the auxiliary temperature Taux (92) generally gives a negative result (NO), and it is the subsequent check S30 on the main temperature Tmain (Tavg) which intervenes to decide whether or switching on the heating device, as represented by the interval A of Figure 2;

[0110] - during or following a withdrawal of water, there is a sudden drop in the auxiliary temperature Taux (32), but not as much as in the main temperature Tmain (Tavg), in such case the pre-check S3 determines whether the drop in the auxiliary temperature Taux (32) may create discomfort conditions and intervenes with priority, compared to the check S30, to switch on the heating device, as represented by the interval B of Figure 2.

[0111] In the interval A, the main temperature Tmain (Tavg) of the water in the storage decreases substantially only due to the heat dispersions through the walls of tank 10 until reaching the switching on temperature Tstart (Tset-Thyst).

[0112] As visible, the auxiliary temperature Taux (32) essentially never reaches the threshold value given by the comfort temperature Tcomf.

[0113] In this case, the pre-check S3 gives a negative result, and the subsequent check S30 switches on the heating device (section C Figure 2) when the main temperature Tmain (Tavg) drops to a value equal to the switching on temperature Tstart (Tset-Thyst), point Al of Figure 2.

[0114] In the interval B instead, the main temperature Tmain (Tavg) is substantially greater than the switching on temperature Tstart (Tset-Thyst), while the auxiliary temperature Taux (32) decreases until it equals the comfort temperature Tcomf, for example following a withdrawal, point Bl of Figure 2; in this case the precheck S3 gives a positive result and switches on the heating device (section D Figure 2).

[0115] It should be noted that without the pre-check S3, the heating device would remain switched off until the main temperature Tmain (Tavg) is less or equal to the switching on temperature Tstart (Tset-Thyst) and meanwhile the lower portion of the storage would continue to cool, creating the conditions for the discomfort, forexample if the user requires hot water for another withdrawal.

[0116] It is therefore reiterated that the pre-check S3, by monitoring the auxiliary temperature Taux, is capable of determining whether a withdrawal is in progress or has just ended, and, by comparing the auxiliary temperature Taux with the comfort temperature Tcomf, whether or not it is necessary to switch on the heating device.

[0117] The method according to the present invention, therefore, allows for:

[0118] - adopting relatively high hysteresis values, thus reducing the cycling at least when there is no withdrawal of water, and

[0119] - at the same time, avoiding discomfort situations for the user by providing for a priority pre-check S3 under the withdrawal request conditions, wherein the auxiliary temperature Taux decreases very quickly, conditions in which, step S30 alone would not make the water heater sufficiently responsive due to the high hysteresis values.

[0120] According to a possible executive embodiment, the possible values taken by the following quantities are provided by way of a non-limiting example:

[0121] - Tavg = a*91 + b*92, with a+b =1 and “a” comprised between 0.5-H, preferably between 0.6-43.9;

[0122] - Tset comprised between 45^-65°C, preferably between 48^-55°C;

[0123] - Tcomf comprised between 25-K35°C, preferably between 28-K32°C.

[0124] The method for controlling the activation / deactivation of a storage water heater or the like according to the present invention, therefore, allows for effectively counteracting / limiting the cycling phenomenon while keeping the water heater responsive and ready in case of a withdrawal.

[0125] The control method according to the present invention, via the pre-check, takes into account the operating conditions of the lower part of the storage and considers them a priority for the switching on of the heating device, with respect to the comparison between the main temperature Tmain of the storage and the set-point temperature Tset set.

[0126] As anticipated, since the value of the auxiliary temperature Taux is highlysensitive and influenced by the presence or not of a withdrawal and by the subsequent make-up of the volume of water withdrawn, the pre-check is capable of indirectly subordinating the switching on of the heating device to the occurrence or not of a withdrawal.

[0127] The logic underlying the control method according to the present invention may be installed on any water heater 1, preferably a heat pump water heater 1, provided with at least one control unit and at least two temperature sensors positioned at different heights along the tank.

[0128] It is clear that several embodiments of the invention described above are possible for the man skilled in the art, without departing from the novelty scopes of the inventive idea, as well as it is clear that in the practical embodiment of the invention the various components described above may be replaced with technically equivalent elements.

[0129] For example, it is possible to adapt the control method described above to particular applications.

[0130] In fact, it has been observed that, during the withdrawals, in water heaters with high power / volume ratios there is a rapid heating up of the storage.

[0131] The rapidity of such heating does not provide the time necessary for the temperature of the storage to homogenise, generating a consequent strong stratification of the same storage, i.e., low temperatures in the lower portion of the storage and high temperatures in the upper portion thereof.

[0132] In such operating conditions there may be a discomfort scenario in the lower portion of the storage, but with temperatures that however remain high in the upper portion.

[0133] In these cases, therefore, the pre-check S3 may detect a discomfort and switch on the heating device, risking the excessive temperature rise in the upper portion of the storage, with possible problems of overheating and / or malfunctions.

[0134] To avoid these switching on not strictly necessary and potentially harmful to the heating device and / or water heater, the method previously described with reference to Figure 3 may provide for an additional check performed in case thepre-check S3 gives a positive / affirmative result.

[0135] As illustrated by way of a non-limiting example in Figure 4, in such case, if the pre-check S3 gives a positive result, the heating device is not switched on as previously seen (step S31), but a further check is carried out, herein referred to as additional control step or additional check S3 O’.

[0136] The additional check S30’ verifies whether said main temperature Tmain is less than or equal to an additional switching on temperature Tstart2.

[0137] According to a preferred embodiment, the additional switching on temperature Tstart2 may correspond to the set-point temperature Tset, preferably to the setpoint temperature Tset to which an additional hysteresis parameter Thyst2, suitably selected / set is subtracted, in order to reduce / avoid frequent and successive switching on of the heating device and possible excessive / anomalous overheating of the water heater, where:

[0138] - if the main temperature Tmain is less than or equal to Tstart2 (Tset-Thyst2), i.e., if the additional check S30’ gives a positive result, the heating device is switched on / activated (HP=ON), so as to bring the storage temperature back to the desired and set temperature Tset, step S31;

[0139] - if the main temperature Tmain is greater than Tstart2 (Tset-Thyst2), i.e., if said additional check S30’ gives a negative result, the heating device remains switched off or in stand-by (HP=OFF), and the first step SI is resumed.

[0140] In such case, the additional hysteresis value Thyst2 is lower than the hysteresis value Thyst used in the third step S30, said Thyst2 being able to be comprised between 2^-5°C, preferably between 2.5- °C.

[0141] As it can be deduced, therefore, the heating device is switched on through the additional check S30’only if the main temperature Tmain is less than or equal to Tstart2, allowing avoiding not strictly necessary switching on which may overheat the water heater, particularly the upper portion of the storage, with consequent possible malfunctions or damages.

[0142] It should be noted that the embodiment of the method described with reference to Figure 4 is essentially the same as the embodiment described with reference toFigure 3, to which the additional check S30’ is added and implemented.

Claims

CLAIMS1. Method for controlling a heating device which may be installed and implemented by a storage water heater (1), said storage water heater (1) comprising at least one heating device, at least one storage tank (10) wherein water is stored and heated, at least one control and management unit capable of controlling at least said at least one heating device, at least one inlet duct (11) through which water may be fed into said tank (10), at least one outlet duct (12) through which water may be sent / withdrawn from said tank (10), said inlet (11) and outlet (12) ducts being in fluid communication with said tank (10),characterised in thatsaid method for monitoring the thermal conditions of the storage comprises acquiring at least:- a main temperature (Tmain), representative of the general thermal state of the water stored in said tank (10),- an auxiliary temperature (Taux), representative of the thermal state of the water in a zone of the said tank (10) wherein there is the mains water refill;and in thatsaid method, having acquired at least said main (Tmain) and auxiliary (Taux) temperatures, proceeding at least to the following execution steps:- first step (SI): checking whether said heating device is switched on;- second step (S3) if the verification of said first step (SI) gives a negative result, a verifying whether said auxiliary temperature (Taux) is less than or equal to a comfort temperature (Tcomf) which may be set by the manufacturer and / or installer and / or user;- third step (S30) if the verification of said second step (S3) gives a negative result, verifying whether said main temperature (Tmain)is less than or equal to a start temperature (Tstart) of said heating device, which may be set by the manufacturer and / or installer and / or user;where, if said third step (S30) gives a positive result, starting said heating device.

2. Method according to the previous claim, in which said main temperature (Tmain) is detected by at least one temperature sensor or calculated as a weighted average of the values detected by at least two sensors placed at different heights inside said tank (10).

3. Method according to the previous claim, in which said main temperature (Tmain) is equal to the average temperature of the water of the storage (Tavg) calculated as: Tavg=a*31 + b*32, where: - a+b=l and “a” comprised between 0.5M;- 91: temperature of the water of the storage in the upper half of said tank (10);- 92: temperature of the water of the storage in the lower half of said tank (10) or in proximity to the inlet zone of the make-up water.

4. Method according to any previous claim, wherein said comfort temperature (Tcomf) is less than or equal to said start temperature (Tstart).

5. Method according to any previous claim, in which said start temperature (Tstart) is equal to a set-point temperature (Tset), a temperature at which the storage may be heated / maintained and may be set by the manufacturer and / or installer and / or user, at which a hysteresis parameter (Thyst) is subtracted, said hysteresis parameter (Thyst) providing for high values comprised between 10^-20°C.

6. Method according to any previous claim, wherein if said second step (S3) gives a positive result, the start of the said heating device is carried out.

7. Method according to any previous claim from 1 to 5, wherein, if saidsecond step (S3) gives a positive result, an additional control step (S30’) adapted to verify whether said main temperature (Tmain) is less than or equal to an additional predefined start temperature (Tstart2) is carried out, where:- if said main temperature (Tmain) is less than or equal to said additional start temperature (Tstart2), starting said heating device, - if said main temperature (Tmain) is greater than said additional start temperature (Tstart2), said heating device remains switched off or in standby and said first step (SI) is resumed.

8. Method according to any previous claim, wherein said additional start temperature (Tstart2) is equal to said set-point temperature (Tset) to which an additional hysteresis parameter (Thyst2) is subtracted, said additional hysteresis parameter (Thyst2) providing for values comprised between 2-^5 °C.

9. Method according to any previous claim, in which if said first step (SI) gives a positive result, the comparison between said main temperature (Tmain) with said set-point temperature (Tset) is carried out, where: - if said main temperature (Tmain) is lower than the set-point temperature (Tset), leaving switched on said heating device and resuming said first step (SI);- if said main temperature (Tmain) is greater than or equal to said set-point temperature (Tset), switching off or placing in stand-by said heating device is.

10. Storage water heater (1) for the production of sanitary hot water, comprising at least one heating device, at least one storage tank (10) in which water is stored and heated, at least one control and management unit capable of controlling at least said at least one heating device, at least one inlet duct (11) through which water may be fed into said tank (10), at least one outlet duct (12) through which water may be sent / withdrawn from said tank (10), said inlet (11) and outlet (12) ductsbeing in fluid communication with said tank (10),characterised in thatit comprises at least:- at least one first temperature sensor (61) capable of detecting the temperature Al of the water of the storage, said first sensor (61) being therefore positioned in a hot zone of the same storage; and - at least one second temperature sensor (62) capable of detecting the temperature 02 of the water of the storage or said auxiliary temperature (Taux), said second sensor (62) being therefore positioned in a cold zone of the same storage or in a zone of the tank in which the make-up water is fed,and in thatit implements, by means of the relative control unit, the control method according to the previous claims 1 to 9.

11. Storage water heater (1) according to the previous claim, wherein said second temperature sensor (62) is placed closer to the water refill zone than said first temperature sensor (61).

12. Storage water heater (1) according to the previous claim, wherein said at least one first temperature sensor (61) is arranged in proximity to the top zone of the said tank (10), while said at least one second temperature sensor (62) is arranged in proximity to the lower zone of said tank (10).

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