Internal heat pump, method for operating an internal heat pump, and control unit for such a heat pump

Abstract

The invention relates to an indoor heat pump (1) configured to be installed inside a building, the heat pump (1) comprising: - a housing (2) accommodating a heat pump circuit (4), - a flammable refrigerant contained in the heat pump circuit (4), - a ventilation pipe (8) and a fan (10) fluidly connected to the ventilation pipe (8), - a gas detector (12) located in the housing (2), and - an electrical control unit (14) referred to as a safety card (14'), the ventilation pipe (8) being arranged to convey air from the interior of the housing (2) to the outside of the building (2) upon activation of the fan (10), the safety card (14') being configured to receive a leak detection signal (LS) from the gas detector (12) and to activate the fan (10) in response to receiving the leak detection signal (LS).The indoor heat pump (1) further comprises a differential pressure sensor (16) configured to detect a pressure difference (DF) between the inside and the outside of the housing (2), wherein the safety card (14') is configured to trigger recurring functional tests (FT) by activating the fan (10) and evaluating a developing pressure difference (DF) measured by the differential pressure sensor (16), wherein the functional test (FT) is passed if the developing pressure difference (DF), in particular depicted as a negative differential pressure, exceeds a predetermined pressure threshold.

Description

[0001] The present invention relates to an indoor heat pump, a method for operating an indoor heat pump and a corresponding control unit.

[0002] Heat pumps are widely known. A heat pump is a device that uses energy to transfer heat from a cool space to a warm space by transferring thermal energy using a refrigeration cycle, cooling the cold space and heating the warm space. Because they transfer heat rather than generate heat, they are more energy-efficient than other heating systems. The refrigeration cycle, also called a heat pump cycle, generally includes a condenser, an evaporator, a compressor, and an expansion device or valve.

[0003] In some cases, it may be desirable to locate the heat pump indoors, i.e., inside a building. So-called indoor heat pumps can use the ambient air within the building, e.g., in a basement, or water as a heat source.

[0004] In recent years, standards and requirements for refrigerants have changed. This includes the requirement for low global warming potential (GWP), in addition to all previous requirements such as safety, practicality, material compatibility, etc.

[0005] To meet the low GWP requirement, flammable refrigerants are used. With flammable refrigerants, there is a risk that a flammable gas mixture will form with the ambient air if the refrigerant escapes from the refrigeration circuit. This risk is particularly high with indoor heat pumps, as the volume of ambient air is limited by the size of the interior. Therefore, even a comparatively small amount of leaked refrigerant can be sufficient to create a dangerous mixture with the ambient air.

[0006] The activation of a fan in the event of a refrigerant leak is known from JPH09324928A. Furthermore, US11092566 B2 discloses an ON / OFF switching of the fan depending on the concentration of the refrigerant in the air.

[0007] However, the state of the art still does not reveal a satisfactory solution, especially in the case of malfunctions of heat pump components.

[0008] Therefore, the object of the invention was to provide an indoor heat pump that can be safely operated with a flammable refrigerant.

[0009] In a first aspect, an indoor heat pump according to claim 1 is proposed. In a second aspect, a method for operating an indoor heat pump according to claim 10 is proposed. In a third aspect, a control unit according to claim 12 is proposed.

[0010] According to the first aspect, an indoor heat pump is proposed which is configured for installation in a building, the heat pump comprising: a housing surrounding a heat pump circuit, a flammable refrigerant contained in the heat pump circuit, a vent pipe with a fan arranged in the vent pipe, a gas detector arranged in the housing, and an electrical control unit referred to as a safety card. The vent pipe is arranged such that, upon activation of the fan, it discharges air from inside the housing to the outside. The safety card is configured to receive a leak detection signal from the gas detector and to activate the fan in response to receiving the leak detection signal. Preferably, the vent pipe vents to the outside of the building in which the heat pump is arranged.

[0011] In one embodiment of the invention, the safety card can be designed as a central control unit for the heat pump. In one possible embodiment, the safety card has at least one circuit board on which at least one processor is arranged to execute all control commands for operating the heat pump. The safety card is part of the electrical components of the heat pump, which are installed on the heat pump as a whole, in particular, arranged within the heat pump housing.

[0012] According to the invention, the indoor heat pump comprises a differential pressure sensor configured to detect a pressure difference between the inside and outside of the housing. The differential pressure sensor compares a pressure detected inside the housing and a pressure corresponding to the ambient pressure detected outside the heat pump housing. The safety card is configured to trigger recurring functional tests by activating the fan and evaluating a developing pressure difference, which is measured by the differential pressure sensor and usually represented as a negative differential pressure. In particular, the functional test is passed if the developing negative differential pressure exceeds a predetermined pressure threshold.

[0013] In a preferred embodiment, the safety card is further configured to activate a safe torque off (STO) of a compressor contained in the heat pump circuit in response to receiving the leak detection signal. Stopping the heat pump circuit preferably counteracts further leakage of refrigerant from the heat pump circuit into the preferably closed housing of the heat pump.

[0014] In a preferred embodiment, the pressure threshold, relative to an ambient pressure measured outside the housing, is -20 Pa or a lower value. The pressure difference between the pressures measured inside the housing and outside the housing is at least 20 Pa or more.

[0015] In a preferred embodiment, the security card is configured so that the recurring functional tests are triggered more frequently than quarterly and less frequently than weekly, in particular between monthly and every two months and in particular every 40 days. This ensures functionality

[0016] In a preferred embodiment, the safety card is configured to receive a test request from an external device, in particular from a primary heat pump in a cluster of heat pumps, and to trigger the functional test in response to the received test request.

[0017] By coordinating the triggering of the functional test by means of the test request in the cluster of heat pumps, it can be prevented that several functional tests of different heat pumps are carried out at the same time, which would jeopardize the integrity of the test execution.

[0018] In a preferred embodiment, the safety card specifies a maximum time between two functional tests and in a case where the maximum time between two functional tests has expired, the functional test is triggered without a test request being received.

[0019] In other words, this implementation describes a fallback position if the test request is not received within the maximum allowable time between two functional tests. If the time expires, the functional test is performed regardless of whether the request was received.

[0020] In a preferred embodiment, the gas detector is located in the lower half of the housing, particularly within the lower 10% of the housing's height. Especially with the refrigerants intended for use, which typically have a higher density than air and are therefore heavier than air, this ensures that any escaping refrigerant can be reliably detected. The gas detector is preferably arranged directly above a housing base defining the operating space for the heat pump circuit.

[0021] In a preferred embodiment, the safety card comprises two input terminals, in particular a first input terminal connected to the gas detector and a second input terminal optionally connected to the differential pressure sensor, and two output relays, in particular a first output relay connected to the fan and a second output relay optionally connected to the safe torque off (STO). The provision of multiple input terminals and output relays on the safety card enables simple and, above all, individual coupling and decoupling of the components to be controlled by the safety card.

[0022] In a preferred embodiment, the indoor heat pump comprises a heat pump control unit configured to control the operation of the heat pump, wherein the heat pump control unit is designed separately from the safety card. By providing a separate heat pump control unit alongside the safety card, it is possible to have specific control commands specifically executed by different control units. Particularly in the event of a defect in one of the control units, the other control unit provides a type of redundancy for at least one emergency operation of the heat pump.

[0023] In a preferred embodiment, the safety card is configured such that, in the event of a failure of a connected component or of the safety card itself, it supplies power to the STO circuit to stop the heat pump cycle and operate the fan until the power to the indoor heat pump is turned off.

[0024] In a preferred embodiment, the safety card includes an additional connector configured to allow the connection of an additional external fan. This additional connector provides a simple way to operate an additional external fan. Particularly in applications where an extended, long ventilation duct system is present connecting to the enclosure's exhaust, the additional fan can be used to ensure the maintenance of the enclosure's ventilation function. The additional connector on the safety card is configured to supply a 230V voltage signal.

[0025] In a preferred embodiment, a non-return valve is arranged in the ventilation pipe, which is designed in particular in such a way that no air flows into the housing of the heat pump via the ventilation pipe.

[0026] In a further aspect, a cluster of indoor heat pumps with at least one indoor heat pump according to the invention and a central control unit is proposed, wherein the central control unit is designed to transmit a test request for carrying out a functional test to the one or more indoor heat pumps.

[0027] In a preferred embodiment of the cluster, the central control unit is designed to coordinate the functional tests of the indoor heat pumps in such a way that at most functional tests of one of the indoor heat pumps connected to the cluster are carried out.

[0028] This prevents the integrity of the functional test from being compromised by parallel functional tests of other heat pumps, and in particular, the reliability of the obtained evaluations of the functional test can be improved.

[0029] According to the second aspect, a method for operating an indoor heat pump is proposed, comprising the following steps: receiving a leak detection signal from a gas detector indicating a flammable refrigerant that has leaked, in particular vaporized, from a heat pump circuit; activating a fan in response to the received gas detection signal, which fan is arranged to evacuate a housing in which a heat pump circuit is located; and repeatedly performing a functional test on the fan.

[0030] The fan function test includes: activating the fan even if no gas is detected; evaluating a pressure difference between the inside and outside of the enclosure; and confirming the safe operation of the indoor heat pump if the detected pressure difference exceeds a specified threshold. Using the steps listed, a safe function check of the fan is possible to verify whether the fan achieves a sufficiently high pressure difference to evacuate the interior of the enclosure in the event of a refrigerant leak from the heat pump.

[0031] In a preferred embodiment, the method further comprises a step of detecting a fault in an electrical control unit referred to as a safety card or a fault in a component connected to the safety card and, if such a fault is detected, activating the fan and deactivating the heat pump, in particular using an STO circuit. This implements a controlled shutdown process for an indoor heat pump and prevents a possible undetected leakage of refrigerant from a heat pump.

[0032] According to the third aspect, a control unit referred to as a security card is proposed, which comprises a printed circuit board and a processor, wherein the control unit comprises program code means configured to carry out the method according to the described second aspect or a preferred embodiment thereof when the program code means are executed by means of the processor.

[0033] Further advantages and embodiments are described with reference to the accompanying drawings, which show the following: Fig. 1: a perspective view of an indoor heat pump according to the invention; Fig. 2: shows a perspective view of the indoor heat pump according to the invention without its housing; Fig. 3: shows a schematic view of the heat pump according to the invention according to Fig. 1 and 2to illustrate the function according to the invention, and Fig. 4: a schematic representation of a security card as a control unit for the function of the heat pump according to the invention. Fig. 1 shows an indoor heat pump 1, which is designed to be installed inside a building (not shown in detail). The heat pump 1 comprises a housing 2, which contains a heat pump circuit 4 ( Fig. 2 ) or surrounds it. In one embodiment of the invention, the housing 2 forms an almost completely closed operating space 6 for the heat pump circuit 4.

[0034] At least one ventilation pipe 8 and a fan 10 connected to the ventilation pipe in a fluid-conducting manner are provided on the housing 2 of the heat pump 1. Furthermore, within the housing 2 and the thus almost closed operating space 6, as Fig. 2can be seen, a gas detector 12 is arranged which is designed to detect a refrigerant that has escaped from the heat pump circuit 4.

[0035] The indoor heat pump 1 further comprises an electrical control unit 14, referred to as a safety card 14', wherein the safety card 14' is at least signal-conductively connected to the gas detector 12 and is configured to receive a leak detection signal LS from the gas detector 12. In one possible embodiment, the electrical control unit 14, designed as a safety card 14', is signal-conductively coupled to the fan 10, wherein the safety card 14' is configured to activate the fan 10 in response to receiving the leak detection signal LS. The ventilation pipe 8 is arranged on the housing 2 such that, upon activation of the fan 10, it evacuates the operating space 6, i.e., conveys air from the interior of the housing 2 to the outside of the housing 2.

[0036] Furthermore, the indoor heat pump 1 comprises a differential pressure sensor 16 configured to detect a pressure difference DF between the interior and exterior of the housing. In a preferred embodiment, the differential pressure sensor 16 is arranged within the housing 2 and has at least two measuring connections 18, 18'. A first measuring connection 18 is connected to the environment outside the housing 2, and a second measuring connection 18' is assigned to the operating space 6, i.e., the interior of the housing 2.

[0037] The safety card 14' is further configured to trigger or execute recurring functional tests FT by activating the fan 10 and evaluating the resulting pressure difference DF, measured by the differential pressure sensor 16, between the interior and exterior of the housing 2. The functional test FT triggered by the safety card 14' is considered passed if the resulting pressure difference DF, in particular depicted as a negative differential pressure, exceeds a predetermined pressure threshold.

[0038] As further stated in Fig. 2As can be seen, the heat pump circuit 4 comprises a compressor 20, an evaporator 22, an expansion valve 24, and a condenser 26. The heat pump circuit 4 supplies thermal energy to a hot water system (hot water connections 28, 28') and a heating system (heating connections 30, 30') that interact with the heat pump 1. The heat pump 1 is supplied with geothermal energy, in particular, via the brine connections 32, 32'.

[0039] According to a preferred embodiment, the gas detector 12 is arranged in the lower half of the housing 2, in particular within the lower 10% of the housing height, preferably directly above a housing base 34 delimiting the operating space 6.

[0040] Fig. 3shows a schematic view of the heat pump 1 with the housing 2 and the safety card 14' arranged within the housing 2, the gas detector 12, the differential pressure sensor 16 and the fan 10 arranged in particular in the ventilation pipe 8. The safety card 14' is further configured, in response to the receipt of a leak detection signal LS triggered by the gas detector 12, to activate the fan 10 in the ventilation pipe to remove the air from the interior of the housing 2 and to initiate a safe torque shutdown STO of the compressor 20 arranged in the heat pump circuit 4.

[0041] The control unit 14, designed as a security card 14', is also configured to trigger or execute the recurring functional tests FT more frequently than quarterly, less frequently than weekly, but in particular at intervals between monthly and every two months, in particular every forty days.

[0042] Fig. 4shows an electrical circuit diagram of the heat pump 1 according to the invention, from which it can be seen that the safety card 14' has two input terminals 40, 40', in particular a first input terminal 40 which is connected to the gas detector 12, and a second input terminal which is optionally connected to the differential pressure sensor 16.

[0043] In one embodiment, the safety card 14' has two output relays 42, 42'. A first output relay 42 is connected to the fan 10 and a second output relay 42' is optionally connected to the torque cut-off STO. As can be seen from Fig. 4As can also be seen, the control unit 14, designed as a safety card 14', is designed separately from a heat pump control unit 50. The heat pump control unit 50 is configured to control the regular operation of the heat pump 1. The safety card 14' is connected to the heat pump control unit 50 via a bus system 52 and is at least configured such that, in the event of an error or failure of the heat pump control unit 50, it at least temporarily enables emergency operation or the safe torque shutdown STO of the compressor 20 of the heat pump circuit 4.

[0044] In particular, the safety card 14' is configured such that, in the event of a failure of a connected component or of the safety card 14' itself, it supplies an STO circuit 44 with power long enough to stop the heat pump circuit 4 in a controlled manner, but to continue operating the fan 10 for at least a predetermined period of time until the power to the indoor heat pump 1 is switched off altogether. As can be seen from Fig. 4 As can also be seen, the safety card 14' has a further connection 46 for a signal-conducting connection with an external fan, not shown in detail.

[0045] Using the Figs. 3 and 4 schematically illustrated safety card 14' and the associated components, such as the gas detector 12 and the differential pressure sensor 16, is an example in Fig. 5shown method 100 for operating an indoor heat pump 1 is possible, which comprises the steps: receiving 102 a leak detection signal LS from a gas detector 12, which indicates a flammable refrigerant that has escaped from a heat pump circuit 4, activating 104 a fan 10, in response to the received leak detection signal LS, which fan is arranged and configured to evacuate a housing 2 in which the heat pump circuit 4 is located, and repeatedly carrying out 106 a functional test FT on the heat pump 1, comprising activating 108 the fan 10, even if no gas is detected, and evaluating 110 a pressure difference DF between an inside and outside of the housing 2, and confirming 112 the safe operation of the indoor heat pump 1 if the determined pressure difference DF exceeds a predetermined pressure threshold value of 20 Pa.The pressure difference DF to be achieved between the inside and outside of the housing 2 during the functional test FT is therefore at least 20 Pa or more.

[0046] The security card 14' comprises at least one circuit board (not shown in detail) and a processor, wherein the security card 14' comprises program code means configured to execute at least the method 100 described above. List of reference symbols

[0047] 1 Indoor heat pump 2 Casing 4 Heat pump circuit 6 Operating room 8 Ventilation pipe 10 Fan 12 Gas detector 14 Control unit 14 Safety card 16 Differential pressure sensor 18, 18' Measuring connection 20 Compressor 22 Condenser 24 Expansion valve 26 Condenser 28, 28' Hot water connection 30, 30' Heating connection 32, 32' Brine connection 40, 40' Input terminals 42, 42' Output relay 44 STO circuit 46 Additional connection 50 Heat pump control unit 100 Procedure 102 Receive LS 104 Activate fan 106 Execute FT 108 Activate fan 110 Evaluate DF 112 Confirm LS Leak detection signal FTFunctional test DFPressure difference STOSafe torque shutdown

Claims

1. An indoor heat pump (1) configured to be installed inside a building, the indoor heat pump (1) comprising: - a housing (2) accommodating a heat pump circuit (4), - a flammable refrigerant contained in the heat pump circuit (4), - a ventilation duct (8) and a fan (10) fluidly connected to the ventilation duct (8), - a gas detector (12) arranged in the housing (2), and - an electrical control unit (14) referred to as a safety card (14'), wherein the ventilation duct (8) is arranged to convey air from the interior of the housing (2) to the outside of the building upon activation of the fan (10), the safety card (14') being configured to receive a leak detection signal (LS) from the gas detector (12) and to activate the fan (10) in response to receiving the leak detection signal (LS). characterized in thatthe indoor heat pump (1) further comprises a differential pressure sensor (16) configured to detect a pressure difference (DF) between the inside and the outside of the housing (2), wherein the safety card (14') is configured to trigger recurring functional tests (FT) by activating the fan (10) and evaluating a developing pressure difference (DF) measured by the differential pressure sensor (16), wherein the functional test (FT) is passed if the developing pressure difference (DF), in particular depicted as a negative differential pressure, exceeds a predetermined pressure threshold.

2. Indoor heat pump (1) according to claim 1, wherein the safety card (14') is further configured to activate a safe torque shutdown (STO) of a compressor (20) included in the heat pump circuit (4) in response to receiving the leak detection signal (LS).

3. Indoor heat pump (1) according to one of the preceding claims, wherein the pressure threshold value is -20 Pa or a lower value.

4. Indoor heat pump (1) according to one of the preceding claims, wherein the safety card (14') is configured to trigger the recurring functional tests (FT) more frequently than quarterly and less frequently than weekly, in particular between monthly and every two months and in particular every 40 days.

5. Indoor heat pump (1) according to one of the preceding claims, wherein the security card (14') is configured to receive a test request from an external device, in particular from a primary heat pump in a cluster of heat pumps, and to trigger the functional test (FT) in response to the received test request.

6. Indoor heat pump (1) according to a combination of claims 4 and 5, wherein the safety card (14') specifies a maximum time between two functional tests and, in a case where the maximum time between two functional tests has expired, to trigger the functional test (FT) without a test request being received.

7. Indoor heat pump according to one of the preceding claims, wherein the gas detector (12) is arranged in the lower half of the housing (2), in particular within the lower 10% of a height of the housing (2).

8. Indoor heat pump according to one of the preceding claims, wherein the safety card (14') has two input terminals (40, 40'), in particular a first input terminal (40) connected to the gas detector (12) and a second input terminal (40') optionally connected to the differential pressure sensor (16), and two output relays (42, 42'), in particular a first output relay (42) connected to the fan (10) and a second output relay (42') optionally connected to the torque shutdown (STO).

9. Indoor heat pump according to one of the preceding claims, comprising a heat pump control unit (50) configured to control an operation of the heat pump (1), wherein the heat pump control unit (50) is formed separately from the security card (14').

10. Indoor heat pump according to one of the preceding claims, wherein the safety card (14') is configured such that, in the event of a failure of a connected component or of the safety card (14') itself, it supplies power to the STO circuit (44) to stop the heat pump circuit (4) and operate the fan (10) until the power to the indoor heat pump (1) is switched off.

11. Indoor heat pump according to one of the preceding claims, wherein the safety card (14') has an additional connection (46) configured for the connection of an additional external fan.

12. Indoor heat pump according to one of the preceding claims, wherein a non-return valve is arranged in the ventilation pipe (8), which non-return valve is designed in particular such that no air flows via the ventilation pipe (8) into the housing of the heat pump.

13. Cluster of indoor heat pumps with at least one indoor heat pump (1) according to one of the preceding claims and a central control unit, wherein the central control unit is designed to transmit a test request for carrying out a functional test (FT) to the one or more indoor heat pumps (1).

14. Cluster according to claim 13, wherein the central control unit coordinates the functional tests (FT) of the indoor heat pumps (1) in such a way that at most functional tests (FT) of one of the indoor heat pumps (1) connected to the cluster are carried out.

15. A method (100) for operating an indoor heat pump (1), comprising the following steps: - receiving (102) a leak detection signal (LS) from a gas detector (12) indicating a flammable refrigerant that has escaped from a heat pump circuit (4), - activating (104) a fan (10) in response to the received leak detection signal (LS), which fan is arranged to evacuate a housing (2) in which the heat pump circuit (4) is located, and - repeatedly carrying out (106) a functional test (FT) on the fan (10), comprising activating (108) the fan (10) even if no gas is detected, and evaluating (110) a pressure difference (DF) between the inside and outside of the housing (2), confirming (112) the safe operation of the indoor heat pump (1) if the determined pressure difference (DF) exceeds a predetermined pressure threshold value exceeds.

16. The method according to claim 15, further comprising a step of - detecting a fault in an electrical control unit (14) referred to as a safety card (14') or a fault in a component connected to the safety card (14'), and - upon detection of such a fault, activating the fan (10) and deactivating the heat pump (1), in particular with the aid of an STO circuit (44).

17. A control unit (14) designated as a security card (14') comprising at least one circuit board and a processor, wherein the control unit (14) comprises program code means configured to execute the method (100) defined in claim 15 or 16 when the program code means are executed by means of the processor.

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