[0001] This invention relates to a water heating system and to a water heating method.
[0002] In prior art water heating systems, the demand for a quantity of hot water is satisfied
using heat pump units having different thermal power ratings. The heat pumps extract
the heat from a source, such as outside air, and then amplify and transfer the heat
where required. The heat pump units include a compressor, an evaporator, a condenser
and an expansion valve, which form a cycle whereby a refrigerant is moved. When the
hot water demand is particularly high, two or more heat pump units are connected in
parallel because a single heat pump cannot deliver the power required. Traditionally,
in water heating systems with a plurality of heat pump units in parallel, all the
units in parallel are turned on simultaneously.
[0003] That method has some disadvantages, however; for example, it is difficult to control
the operating state of all the heat pump units when they are all working at the same
time.
[0004] Moreover, in that method, it is not possible to determine the number of units that
need to be activated to satisfy the real hot water demand; that means a lot of energy
is wasted.
[0005] In this context, patent document
CN202403412 describes an energy-saving heat pump system in which a master control unit is connected
to a slave heat pump unit through a master-slave communication system. However, that
document does not provide further details as to how the slave unit is controlled by
the master control system.
[0006] Furthermore, patent document
CN104748393 describes a heat pump system having a plurality of heat pumps connected to each other.
[0007] The plurality of units comprises a main unit having a main controller and a plurality
of sub-units having a plurality of secondary controllers. After receiving the power-on
signal, the main controller detects a working condition parameter of the water tank
and determines whether the working condition parameter of the water tank satisfies
the first preset power-on condition. If the working condition parameter of the tank
meets the first power-on condition, the main controller detects whether the working
condition parameter of the total flow path meets the second preset power-on condition
and, if the working condition parameter of the total flow path meets the third preset
power-on condition, the main controller sends a power-on command to the plurality
of secondary controllers; each of the secondary controllers detects a working condition
parameter of a branch corresponding to it and determines whether the working condition
parameter of the branch meets the third preset power-on condition; if the working
condition parameter of the branch meets the third preset power-on condition, the heat
pump corresponding to the branch is started. Furthermore, patent document
CN 107 062 589 A describes a water heating system comprising a plurality of heat pumps, where each
heat pump unit includes: a water tank, in which the heat pump unit is operable in
an ON mode, in which the heat pump is active to heat the water in the tank, and an
OFF mode, in which the heat pump is inactive; a water inlet and a water outlet in
communication with each other to form a main water outlet; a solenoid valve at the
water outlet or at the water inlet; a temperature sensor; a control unit, connected
to the solenoid valve and to the temperature sensor; and a bus, where the control
units are interconnected by the bus to exchange data.
[0008] However, the water heating pump systems of the prior art have some disadvantages
and can be improved. In effect, there are several needs in this field.
[0009] One need is to provide a water heating system capable of supplying the required quantity
of hot water with greater efficiency and reliability. Another need is to improve the
water heating system by extending its working life. Another need is to provide a water
heating system that is more energy efficient.
[0010] The aim of this disclosure is to provide a water heating system and a water heating
method to overcome the above mentioned disadvantages of the prior art.
[0011] This aim is fully achieved by the system and method of this disclosure as characterized
in the appended claims.
[0012] According to an aspect of it, this disclosure provides a water heating system. The
water heating system (or the system for short) comprises a plurality of heat pump
units. Each heat pump unit (or each unit for short) includes a water tank. Each heat
pump unit operates in an ON mode and in an OFF mode. In the ON mode, the heat pump
is active to heat the water in the tank. In the OFF mode, the heat pump is inactive.
Each unit includes a water inlet. Each unit includes a water outlet. The water outlets
of the units are in communication with each other to form a main water outlet.
[0013] Each unit may include a solenoid valve. The solenoid valve is located at the water
outlet or at the water inlet. Each unit includes a temperature sensor. The temperature
sensor is configured to detect the temperature of the water inside the water tank.
[0014] Each unit includes a control unit. The control unit is connected to the solenoid
valve. The control unit is connected to the temperature sensor.
[0015] In an example, the water heating system comprises a bus. The control units are interconnected
through the bus to exchange data. The heat pump units may be interconnected using
different buses, for example, CAN-bus or Profibus.
[0016] The control units are programmed so that one of the heat pump units acts as a master
unit and the remaining units act as slave units.
[0017] The master unit is programmed to derive an operative number. The operative number
is derived in response to a hot water demand. The operative number is the required
number of heat pump units working in ON mode needed to satisfy the hot water demand.
The master unit is configured to turn on one or more heat pump units based on the
derived operative number. The master unit is also configured to activate the solenoid
valve of one or more of the heat pump units. The master unit activates the solenoid
valve of one or more of the heat pump units responsive to the hot water demand.
[0018] Therefore, according to an aspect of this disclosure, the slave units are controlled
by the master unit and the master unit derives the number of units which must operate
in the ON mode to satisfy the hot water demand. Furthermore, the number of active
valves corresponds to the number of units which are ON. This solution provides higher
energy efficiency because the master unit turns on only the number of units needed
to meet the hot water demand. It should be noted that the open valves may belong to
the units working in the ON mode or to those in the OFF mode. Moreover, the fact that
each unit includes a solenoid valve allows preventing the cold water that may be present
in the unit from being mixed with the hot water available in the other units.
[0019] In an example, all the heat pump units have the same hardware.
[0020] The master unit is configured to receive data relating to the temperature of the
water tank of each heat pump unit. The master unit is also configured to activate
the solenoid valves of the heat pump units with the highest detected water tank temperature.
[0021] According to this solution, only the solenoid valves of the units with the highest
detected temperature (in which the tank contains water with the highest temperature)
are activated, even if these units are not ON; this solution thus allows having a
water heating system that is more reliable and more efficient, capable of providing
the hot water required.
[0022] In another example, the master unit may be configured to open the solenoid valves
based on other criteria.
[0023] In an example, the heat pump units are connected in parallel. The master unit may
be configured to associate a ranking code with each heat pump unit. The master unit
may also be configured to turn on the heat pump units, sequentially, as a function
of the ranking code of each unit, for a predetermined time interval.
[0024] Furthermore, at the end of the predetermined time interval, the master unit is configured
to assign the ranking code of each heat pump unit to the adjacent one.
[0025] The master unit may be configured to turn on the heat pump units based on the ranking
code and starting from the smallest ranking code.
[0026] Therefore, according to an aspect of this disclosure, in each interval (predefined
minutes, hours or days), at least one of the units that was in the ON mode in the
previous interval remains inactive in the OFF mode: all the units have the same wear
rate, thus increasing the working life of the system. It should be noted that if all
the heat pump units need to be in operation in a particular interval, none of the
units remains inactive in the OFF mode.
[0027] It should be noted that this disclosure also contemplates an example in which the
units may be switched on sequentially based on their ranking code, and the solenoid
valves are not necessarily the solenoid valves of the units with the highest detected
temperature (as explained above) but they may be chosen by the master unit based on
other criteria.
[0028] The heat pump units each possess a serial code. The serial code is unique for each
heat pump unit. Moreover, the serial code is always the same for each heat pump unit.
In an example, the master unit is programmed to detect the serial code of each heat
pump. The master unit uses the serial code as an identification code. In an example,
for each heat pump unit, the serial code and the corresponding ranking code are stored
in a database. The serial codes and the corresponding ranking codes may be stored
in a memory of the control unit of the master unit. The serial codes and the corresponding
ranking codes stored in the database determine the sequence according to which the
heat pump units are turned on by the master unit. Furthermore, the ranking codes associated
with the serial codes may be modified dynamically as a function of one or more predetermined
criteria. The predetermined criteria may be, for example: the number of hours or days
of operation, or the number of times each heat pump unit has been switched on.
[0029] In an example, the master unit is configured to detect faulty heat pump units. The
master unit is configured to assign the ranking code of a faulty unit to the unit
adjacent to it.
[0030] This solution allows obtaining a system that is capable of delivering the required
amount of hot water in a reliable manner.
[0031] In an example, the number of activated solenoid valves corresponds to the number
of heat pump units operating in ON mode.
[0032] In an example, the master unit is configured to derive the operative number and to
turn on said one or more heat pump units responsive to a plurality of intervals of
hot water demand. In an example, a predetermined operative number is associated with
each interval, so that in each interval of hot water demand a predetermined number
of heat pump units work in the ON mode.
[0033] This solution allows having a water heating system that is more reliable and more
efficient, capable of providing the hot water required.
[0034] In an example, the predetermined operative number of each interval is selectable
by a user.
[0035] In an example, the master unit is configured to detect faulty heat pump units. In
the case where the number of faulty units exceeds the derived operative number, the
master unit is configured to turn on all the remaining heat pump units.
[0036] This solution allows improving the reliability and efficiency of the system.
[0037] It is therefore possible to enhance the reliability and efficiency of the system.
[0038] It should be noted that this disclosure provides an example in which the master unit
is configured to turn on all the units which are not faulty in the case where the
number of faulty units exceeds the derived operative number, and where the units are
turned sequentially based on their ranking codes or on other criteria.
[0039] In an example, if the connection between the master and the slave units fails, the
master unit is configured to continue working in a predetermined mode as a standalone
heat pump unit with activated solenoid valve. Moreover, if the connection between
the master and the slave units fails, the slave units which are not faulty continue
working according to a predetermined setting. In particular, each heat pump unit has
the set parameters which determine the function of the unit in the event of its failing
to communicate with the master unit.
[0040] Each heat pump unit may have different modes. The modes of the heat pump units may
include ON, OFF and STANDBY. In an example, in the standby mode, the water is heated
by external heat sources such as, for example, thermal or photovoltaic solar panels.
In an example, in the ON mode, the water is heated using power delivered directly
by the heat pump.
[0041] According to an aspect of it, this disclosure provides a method for heating water.
The method comprises a step of providing a water heating system. The water heating
system comprises a plurality of heat pump units. Each heat pump unit (or unit for
short) includes a water tank. Each heat pump unit is operable in an ON mode and in
an OFF mode. In the ON mode, the heat pump is active to heat the water in the tank.
In the OFF mode, the heat pump is inactive.
[0042] Each unit includes a water inlet. Each unit includes a water outlet. The water outlets
of the heat pump units are in communication with each other to form a main water outlet.
[0043] Each unit includes a solenoid valve. The solenoid valve is located at the water outlet
or inlet.
[0044] Each unit includes a temperature sensor. The temperature sensor is configured to
detect the temperature of the water inside the water tank. Each unit includes a control
unit. In each unit, the control unit is connected to the solenoid valve and to the
temperature sensor.
[0045] The water heating system also comprises a bus. The control units are interconnected
through the bus to exchange data.
[0046] The method comprises a step of running one of the heat pump units as a master unit
and the remaining units as slave units.
[0047] The method comprises a step of deriving an operative number. The operative number
is derived in response to a hot water demand. The operative number is the number of
heat pump units working in ON mode needed to satisfy the hot water demand.
[0048] The method comprises a step of turning on one or more heat pump units, through the
master unit, based on the derived operative number.
[0049] The method comprises a step of activating the solenoid valve of one or more of the
heat pump units, through the master unit, responsive to the hot water demand. In an
example, the number of activated solenoid valves may correspond to the number of heat
pump units operating in ON mode. In an example, the master unit receives data relating
to the temperature of the water tank of each heat pump unit. In an example, the master
unit activates the solenoid valves of the heat pump units with the highest detected
water tank temperature.
[0050] In an example, the method comprises a step of connecting the heat pump units in parallel.
The method may comprise a step of associating a ranking code with each heat pump unit,
through the master unit.
[0051] In an example, the method comprises a step of turning on the heat pump units, sequentially,
based on the ranking code of each unit, for a predetermined time interval.
[0052] Furthermore, at the end of the predetermined interval, the ranking code of each unit
is assigned to the adjacent one, through the master unit.
[0053] In an example, the heat pump units are turned on based on the ranking code of each
unit and starting from the smallest ranking code.
[0054] In an example, the method comprises a step of turning ON said one or more heat pump
units, through the master unit, responsive to a plurality of intervals of hot water
demand, where a predetermined operative number is associated with each interval, so
that in each interval of hot water demand, a predetermined number of heat pump units
work in the ON mode.
[0055] These and other features will become more apparent from the following description
of a preferred embodiment, illustrated purely by way of nonlimiting example in the
accompanying drawings, in which:
- Figure 1 illustrates a water heating system according to this disclosure;
- Figure 2 illustrates the system with the units in the ON and OFF modes;
- Figures 3A and 3B illustrate the system in two different intervals;
- Figure 4 illustrates a heat pump of each unit of the system;
- Figure 5 illustrates the water heating system in combination with a thermal solar
system.
[0056] With reference to the accompanying drawings, the numeral 1 denotes a water heating
system. The water heating system 1 (or the system, for short) includes a plurality
of heat pump units 2. Each heat pump unit 2 (or the unit, for short) includes a heat
pump 100. The heat pump 100 includes a compressor 101. The compressor 101 has an inlet.
The compressor also includes an outlet. The compressor 101 is configured to increase
the pressure of a refrigerant.
[0057] The heat pump 100 also includes an evaporator 102. The evaporator has an inlet. The
inlet of the evaporator 102 receives the refrigerant in the liquid state. The evaporator
102 also includes an outlet. The evaporator outlet is used to release the refrigerant
in the gaseous state. The evaporator receives a heat flow in a space adjacent thereto.
The evaporator receives the heat flow from a fluid.
[0058] The heat pump 100 also includes an expansion valve 103. The expansion valve 103 is
used to expand the refrigerant.
[0059] The heat pump includes a condenser 104. The condenser receives the refrigerant in
the gaseous state. The condenser releases the liquid refrigerant at a low temperature.
Each unit includes a water tank T.
[0060] The condenser 104 is located inside or outside the water tank T. The water tank of
each unit 2 contains water to be heated by heat exchange with the condenser 104. Each
heat pump unit works in an ON mode, in which the heat pump 100 is active to heat the
water in the tank T, and an OFF mode, in which the heat pump 100 is inactive. Furthermore,
each unit can also work in a STANDBY mode, in which the water is heated by external
heat sources such as, for example, thermal or photovoltaic solar panels. Each unit
includes a water inlet I and a water outlet O. The water inlet is connected to the
water tank T and receives the water to be heated. The water outlets of the heat pump
units are in communication with each other to form a main water outlet MO. Each unit
also includes a solenoid valve V connected to the water outlet or inlet. In each unit,
the temperature of the water inside the tank T is detected by a temperature sensor
S. Each unit includes a control unit C. The control unit is connected to the solenoid
valve V and to the temperature sensor S. The control units C of the plurality of heat
pump units 2 are connected to each other through a bus so as to exchange data. One
of the control units is programmed to work as a master control unit and controls the
other control units, which work as slave control units.
[0061] Therefore, the unit with the master control unit works as master unit 2A and the
units with the slave control units work as slave units 2B. The master unit derives
an operative number responsive to a hot water demand and turns on one or more heat
pump units 2 based on the derived operative number. The operative number is the required
number of heat pump units which need to work in ON mode to satisfy the hot water demand.
The master unit 2A activates the solenoid valve of one or more of the heat pump units.
The number of activated solenoid valves may correspond to the number of heat pump
units operating in ON mode. In particular, the master unit may derive the operative
number responsive to a plurality of water demand intervals. For example, the plurality
of water demand intervals may include a minimum level, an intermediate level and a
maximum level. The master unit derives the operative number for each of these levels.
In an example, a predetermined operative number is associated with each interval.
Therefore, in each hot water demand interval, a predetermined number of heat pump
units must work in the ON mode. For example, the system may have a database in which
the operative number is saved for each hot water level (that is, the level of hot
water demand) which is entered in the system. The operative number may be selected
by a user and can be modified. Therefore, when the hot water demand level is entered
in the master unit, the master control unit selects the predetermined operative number
of that level and turns on the units 2 based on the selected operative number.
[0062] The master unit receives the temperature of the water tank, detected by the sensor
S, of each heat pump unit and activates the solenoid valve V of the heat pump units
with the highest detected temperature. Therefore, the valves which are active may
be the valves not only of the units 2 which are switched on but also those of the
units which are switched off. For example, if the plurality of units includes three
units and the operative number entered for the hot water demand is two, the master
unit turns on two heat pump units 2; in addition, the master unit 2A checks the temperature
of the water in all the units (including itself) and opens the solenoid valves of
the units with the highest temperature. Figure 2 shows an example in which the units
which are switched on include the master unit and one slave unit but only the valves
of the slave units are open, since the temperature of the master unit (45°C) is lower
than that of the slave unit which is switched off (52°C). Thus, before opening the
solenoid valves, the master checks all the units to identify which valves must be
opened. The heat pump units 2 may be connected in parallel. The master unit 2A associates
a ranking code with each heat pump unit, including itself, and turns on the units
sequentially for a predetermined time interval. At the end of the predetermined time
interval, the master unit assigns the ranking code of each heat pump unit to the adjacent
one. The ranking code determines the order in which the units are turned on. In particular,
the ranking code determines the position of each heat pump unit in the ranking which
determines the order in which the units are turned on. For example, as shown in Figure
3A (an example in which the operative number is two), the master unit 2A and the slave
unit 2B adjacent to the master unit, with the ranking codes 1 and 2, respectively,
are switched on and working in the ON mode. When the predetermined time interval comes
to an end, each unit receives the ranking code of the unit preceding it, and as shown
in Figure 3B, the master unit switches off and the two slave units 2 work in ON mode.
[0063] The heat pump units each possess a serial code. The serial code is unique for each
heat pump unit. Moreover, the serial code is always the same for each heat pump unit.
In an example, the master unit is programmed to detect the serial code of each heat
pump. The master unit uses the serial code as an identification code. In an example,
for each heat pump unit, the serial code and the corresponding ranking code are stored
in a database. The serial codes and the corresponding ranking codes may be stored
in a memory of the control unit of the master unit. The serial codes and the corresponding
ranking codes stored in the database determine the sequence according to which the
heat pump units are turned on by the master unit. Furthermore, the ranking codes associated
with the serial codes may be modified dynamically as a function of one or more predetermined
criteria. The predetermined criteria may be, for example: the number of hours or days
of operation, or the number of times each heat pump unit has been switched on.
[0064] Therefore, the serial code of each heat pump unit may be associated with a ranking
code and this data is stored in the database. This data stored in the database is
subsequently used by the control unit of the master unit and the heat pump units are
turned on sequentially and according to the ranking code stored in the database. At
the end of every interval, the database is updated and the ranking code of each heat
pump unit is changed. For example, at the end of the predetermined time interval,
each heat pump unit receives the ranking code of the adjacent unit. In an example,
the ranking codes are assigned to all the heat pump units, including the master unit.
[0065] In the event of one (or more) faulty units 2, the master unit 2A detects it and assigns
its ranking code to the unit adjacent to the faulty unit. If the number of faulty
units exceeds the derived operative number, the master unit turns on all the remaining
heat pump units. If the connection between the master unit 2A and the slave units
2B fails, the master unit continues to work in the ON mode as a standalone heat pump
unit and the solenoid valve V of the master unit remains open.
[0066] Moreover, if the connection between the master and the slave units fails, the slave
units which are not faulty continue working according to a predetermined setting.
In particular, each heat pump unit has the set parameters which determine the function
of the unit in the event of its failing to communicate with the master unit.
[0067] Each heat pump unit may have different modes. The modes of the heat pump units may
include ON, OFF and STANDBY. In an example, in the standby mode, the water is heated
by external heat sources such as, for example, thermal or photovoltaic solar panels.
In an example, in the ON mode, the water is heated using power delivered directly
by the heat pump. When there is no communication with the master unit, each (non-faulty)
unit continues to work in one of the modes determined for that unit in the event of
a failed connection. For example, a slave unit may be configured to continue working
in standby mode if it loses its connection with the master unit.
[0068] In particular, if the master unit 2A interrupts the connection between it and a slave
unit 2B, the master unit is configured to identify the unit whose connection it has
lost as a faulty unit and to exclude it from the heating system. In this case, a code
identifying the fault appears on the display of the master unit.
[0069] The master unit is also configured to cyclically retry communicating with the slave
unit identified as faulty in order to check whether the connection has been re-established.
In this case, the slave unit is re-included in the control logic of the heating system.
[0070] If the slave unit 2B interrupts the connection between it and the master unit 2A,
the slave unit, after a predetermined time interval, continues to work as a standalone
heat pump unit in a predefined mode.
[0071] In this case, a code identifying the fault appears on the display of the slave unit.
[0072] Furthermore, if communication with the master unit is re-established, the slave unit
returns to being controlled by the master unit.
[0073] In the event of a fault in any unit (whether master or slave), if the fault is such
as to prevent its operation, that unit is identified as faulty and the master unit
excludes it from the control logic of the heating system.
[0074] It should be noted that even when the master unit is affected by a fault which prevents
it from operating but which nevertheless allows cascade control (controlling the plurality
of interconnected heat pump units), the master unit is identified as faulty and excluded
from the heating system (and used only to control the other units).
[0075] In this case, a code identifying the fault appears on the displays of both the master
unit and the slave unit.
[0076] In particular, a code identifying the fault is displayed on the unit affected by
the fault.
[0077] In an example, each of the heat pump units is configured to perform a plurality of
auxiliary functions. In particular, even when the heat pump unit is configuration
to be integrated in the water heating system according to this disclosure (water heater
cascade heating system), it may control these auxiliary functions, independently of
the configuration of the other units. The term "water heater cascade heating system"
is used to mean a water heating system having a plurality of interconnected heat pump
units in which one or more slave units are controlled by a master unit. Th plurality
of auxiliary functions includes at least one of the following functions:
- Antifreeze function
- Antilegionella function
- Thermal solar function
- EVU function
- Photovoltaic function
- Smart-grid function
[0078] In the case of the antifreeze function, each unit is configured to continue controlling
this function as if it were working as a standalone unit independent of the cascade
heating system.
[0079] As regards the antilegionella function, when this function is enabled and the unit
is programmed to work in cascade (according to this disclosure), irrespective of whether
it is configured as a slave unit or as the master unit, the antilegionella function
is always activated after a predetermined time delay, as occurs when the unit is working
as a standalone unit. Even if the temperature of the water in the tank T reaches a
certain setpoint for legionella disinfection during this time delay, the antilegionella
function is not activated until the time delay has elapsed.
[0080] Moreover, to prevent this function from being enabled simultaneously on two or more
units, leading to excessive consumption, at each power-on, each unit initializes its
own counter which counts the days which have passed between one antilegionella cycle
and another and based on its own ranking code.
[0081] As regards the thermal solar function, a thermal solar system may be provided for
use in combination with the cascade function according to this disclosure.
[0082] In particular, Figure 5 illustrates the water heating system 1 according to this
disclosure, combined with a thermal solar system.
[0083] The thermal solar system includes a solar panel 3 and a temperature probe 4. In particular,
the probe 4 is connected to the motherboard of the master unit 2A.
[0084] The thermal solar system also includes a solar pump 5 which must be connected to
the control unit of the master unit 2A. The electric power supply of the solar pump
5 must be regulated by solar safety thermostats 6 (one for each unit) which must be
connected in series. This solution allows stopping the solar pump in the event of
overheating of one of the heat pump units.
[0085] In particular, to avoid both installation complexity and excessive cost of components,
the cascade function of the heating system is capable of monitoring the temperature
of the thermal solar panels 3 through the temperature probe 4 (one probe only) and
controlling the circulation of the water between solar panels and a solar coil 105
of the unit (each unit) through the pump 5 (one pump only). The probe and the pump
are physically connected to the master unit which controls their operation. The master
unit transmits the temperature of the probe 4 to the slave units and controls the
circulation pump, even if only one unit of the plurality of units requires its use
with a solar panel, thus allowing each unit to control this function as if it were
working as a standalone unit (independent of other units).
[0086] As regards the EVU function, like the thermal solar function, to avoid both installation
complexity and excessive cost of components, if electrical energy is provided under
a reduced rate contract and it is to be used in combination with the cascade function,
the cascade function is capable of controlling the device supplied by the energy provider
by connecting the provider's device only to the unit configured as master unit.
[0087] In particular, the master unit is configured to transmit to the slave units the state
of the digital input assigned to the EVU function, thus allowing each unit to control
this function as if the unit were working as a standalone unit. As regards the photovoltaic
function, to avoid both installation complexity and excessive cost of components,
a photovoltaic system may be provided for use in combination with the cascade function.
In this case, the cascade function is capable of controlling the state of the system
using only the digital input of the unit configured as master unit.
[0088] The master unit transmits to the slave units the state of the digital input assigned
to the photovoltaic function, thus allowing each unit to control this function as
if the unit were working as a standalone unit.
[0089] As regards the smart grid function, a SMART GRID function may be used in combination
with the cascade function. In such an example, the cascade function is capable of
controlling the different states of the SMART GRID using only the digital inputs of
the unit configured as master unit.
[0090] In this case, the master unit transmits to the slave units the current state of the
SMART GRID, thus allowing each unit to control this function as if the unit were working
as a standalone unit.
[0091] It should be noted that if a slave unit 2B interrupts the connection between it and
the master unit 2A, as explained above, the slave unit, after the predetermined time
interval, continues to work as a standalone heat pump unit in a predefined mode and
the auxiliary, thermal solar, EVU, photovoltaic and Smart Grid functions are disabled
because the master unit would no longer be able to receive the reading of the solar
panel probe and the state of the digital inputs.
1. A water heating system (1), comprising a plurality of heat pump units (2), wherein
each heat pump unit includes:
- a water tank (T), wherein the heat pump unit is operable in an ON mode, wherein
the heat pump is active to heat the water in the tank (T), and an OFF mode, wherein
the heat pump is inactive;
- a water inlet (I) and a water outlet (O), wherein the water outlets of the heat
pump units communicate with each other to form a main water outlet (MO);
- a solenoid valve (V) at the water outlet (O) or the water inlet (I);
- a temperature sensor (S), for detecting the temperature of the water inside the
water tank;
- a control unit (C), connected to the solenoid valve (V) and to the temperature sensor,
the water heating system further comprising a bus, wherein the control units are interconnected
through the bus to exchange data, and being characterized in that the control units are programmed so that one of the heat pump units (2) acts as a
master unit (2A) and the remaining units act as slave units (2B),
wherein the master unit is programmed to derive an operative number responsive to
a hot water demand, the operative number being the required number of heat pump units
working in ON mode to satisfy the hot water demand, and wherein the master unit is
programmed to turn on one or more heat pump units (2) based on the derived operative
number, the master unit being further programmed to activate the solenoid valve of
one or more of the heat pump units, responsive to the hot water demand.
2. The water heating system (1) according to claim 1, wherein the master unit is configured
to receive data relative to the water tank temperature of each heat pump unit and
to activate the solenoid valve (V) of the heat pump units with the highest detected
water tank temperature.
3. The water heating system (1) according to claim 2, wherein the heat pump units (2)
are connected in parallel, and the master unit (2A) is programmed to associate a ranking
code with each heat pump unit, the master unit being further programmed to turn on
the heat pump units, sequentially, based on the ranking code of each unit, for a predetermined
time interval, wherein at the end of the predetermined time interval, the master unit
is configured to assign the ranking code of each heat pump unit to the adjacent one.
4. The water heating system (1) according to claim 3, wherein the master unit is configured
to detect faulty heat pump units and to assign the ranking code of each faulty unit
to the adjacent unit.
5. The water heating system (1) according to any of the previous claims, wherein the
number of activated solenoid valves corresponds to the number of heat pump units operating
in ON mode.
6. The water heating system (1) according to any of the previous claims, wherein the
master unit is configured to derive the operative number and to turn on said one or
more heat pump units responsive to a plurality of intervals of hot water demand, wherein
a predetermined operative number is associated with each interval, so that in each
interval of hot water demand a predetermined number of heat pump units work in the
ON mode.
7. The water heating system (1) according to claim 6, wherein the predetermined operative
number of each interval is selectable by a user.
8. The water heating system (1) according to any of the previous claims, wherein the
master unit is configured to detect faulty heat pump units and, if the number of faulty
units exceeds the derived operative number, the master unit is configured to turn
on all remaining heat pump units.
9. The water heating system (1) according any of the previous claims, wherein, if the
connection between the master and the slave units fails, the master unit is configured
to continue working in the ON mode as a standalone heat pump unit with activated solenoid
valve.
10. A method for heating water comprising the following steps:
- providing a water heating system (1) comprising a plurality of heat pump units (2),
wherein each heat pump unit includes:
a water tank (T), wherein the heat pump unit is operable in an ON mode, wherein the
heat pump is active to heat the water in the tank, and an OFF mode, wherein the heat
pump is inactive;
a water inlet (I) and a water outlet (O), wherein the water outlets of the heat pump
units communicate with each other to form a main water outlet (MO);
a solenoid valve at the water outlet (O) or at the water inlet (I);
a temperature sensor (S), for detecting the temperature of the water inside the water
tank;
a control unit (C), connected to the solenoid valve and to the temperature sensor,
wherein, the water heating system further comprises a bus, wherein the control units
are interconnected through the bus to exchange data,
characterized in that the method further comprises the following steps:
- running one of the heat pump units (2) as a master unit (2A) and the remaining units
as slave units (2B),
- deriving an operative number responsive to a hot water demand, the operative number
being the required number of heat pump units working in ON mode needed to satisfy
the hot water demand,
- turning on one or more heat pump units (2), through the master unit, based on the
derived operative number,
- activating the solenoid valve of one or more of the heat pump units, through the
master unit, responsive to the hot water demand.
11. The method according to claim 10, wherein the master unit receives data relative to
water tank temperature of each heat pump unit and activates the solenoid valve of
the heat pump units with the highest detected water tank temperature.
12. The method according to claim 10 or 11, comprising the following steps:
- connecting the heat pump units in parallel;
- associating a ranking code with each heat pump unit, through the master unit;
- turning on the heat pump units, sequentially, based on the ranking code of each
unit, for a predetermined time interval,
- at the end of the predetermined interval, assigning the ranking code of each heat
pump unit to the adjacent one, through the master unit.
13. The method according to any of the previous claims from 10 to 12, comprising a step
of turning ON said one or more heat pump units, through the master unit, responsive
to a plurality of intervals of hot water demand, wherein a predetermined operative
number is associated with each interval, so that in each interval of hot water demand
a predetermined number of heat pump units work in the ON mode.