Heating a condensate tray in a heat pump

Abstract

The present invention relates to a method for heating a condensate tray of a heat pump and to a heat pump. The method for heating a condensate tray of a heat pump, wherein the heat pump comprises an evaporator and a condensate tray heater, and the condensate tray is designed to collect condensate falling from the evaporator, comprises the following steps: obtaining a run-on time for the condensate tray heater (3), heating (S101) the condensate tray (2) by the condensate tray heater (3) at the start of the defrosting process of the evaporator, stopping (S102) the heating of the condensate tray (2) by the condensate tray heater (3) after the defrosting process of the evaporator has been stopped by the control electronics, and the run-on time, which begins to run when the defrosting process of the evaporator has been stopped by the control electronics, has elapsed.

Description

[0001] The present invention relates to a method for heating a condensate tray of a heat pump and to a heat pump.

[0002] Heat pumps use the heat available in the environment to heat buildings and provide hot water. Suitable energy sources for this include geothermal energy, groundwater, or the ambient air. Air-to-water heat pumps, which use the energy from the ambient air to heat water for heating and / or drinking water, are interesting for both renovations and new builds due to their low installation costs. A disadvantage of this type of heat pump, however, is that at low temperatures the water contained in the air can condense as ice on the heat exchanger, also known as the evaporator. For this reason, the evaporator must be defrosted regularly. Depending on the device type, the water produced during defrosting can be collected in a condensate tray below the evaporator and drained away.

[0003] In the simplest units, a recess is provided in the base plate below the evaporator through which the condensate can drip out of the unit. One disadvantage is that, particularly in winter, large areas of ice can form near the unit. Depending on the installation location, this can pose a risk of injury or create an undesirable appearance.

[0004] However, especially higher-priced devices have a condensate tray in which the water is collected and drained away via a nozzle.

[0005] Since the condensate water has a temperature just above 0 °C during defrosting, it can easily refreeze if it drips onto the condensate tray. This can occur especially if outside temperatures remain below 0 °C for an extended period, causing the temperature of the condensate tray to also drop below 0 °C.

[0006] Contamination in the condensate tray, for example from leaves, negatively affects the water flow rate, which can promote icing.

[0007] It becomes problematic when a growing, multi-layered layer of ice forms over several defrost cycles. This occurs especially when contaminants clog the drain or narrow it to the point where it freezes over.

[0008] In some heat pumps, especially those with higher-end features, the condensate tray is continuously heated by the refrigerant circuit. This is achieved by a so-called defrost coil. The defrost coil is a copper pipe that runs in a curve along the entire length of the condensate tray. In the refrigerant circuit, the defrost coil is located upstream of the evaporator's expansion valve. Accordingly, the refrigerant in it is still at a temperature higher than the freezing point of water.

[0009] The energy required to keep the system ice-free is provided by subcooling the refrigerant, which is thermodynamically efficient. The brass nozzle also serves to heat the drain.

[0010] In contrast to keeping ice free using refrigerants, the heating of the condensate pan can be controlled methodically using an electric condensate pan heater, which allows for demand-based control.

[0011] Against this background, the object of the invention is to provide a controllable and as efficient as possible condensate pan heating system.

[0012] According to a first aspect of the invention, a method for heating a condensate pan of a heat pump is provided to achieve the object set by the invention, wherein the heat pump comprises an evaporator and a condensate pan heater and the condensate pan is designed to collect condensate falling on the evaporator, wherein the method comprises the following steps: obtaining a run-on time of the condensate pan heater, heating the condensate pan by the condensate pan heater when the defrosting process of the evaporator starts, ending the heating of the condensate pan by the condensate pan heater after the defrosting process of the evaporator has ended by the control electronics and expiration of the run-on time, which begins to run when the defrosting process of the evaporator is ended by the control electronics.

[0013] A method according to the invention is preferably carried out by the control electronics of a heat pump. The control electronics are therefore preferably designed to control the condensate pan heating. Such control includes, among other things, starting and stopping the heating of the condensate pan.

[0014] Control of the condensate pan heater by the control electronics enables demand-based operation. Heating of the condensate pan by the condensate pan heater begins when the evaporator defrost process is initiated by the control electronics. The condensate pan heater stops heating of the condensate pan when the defrost process is completed by the control electronics and the run-on time, which begins when the evaporator defrost process is completed by the control electronics, results in energy-saving, efficient operation.

[0015] Continuously switching on the condensate pan heater at freezing temperatures would reduce the heat pump's efficiency. Targeting the heating only during evaporator defrosting, when water falls into the condensate pan, increases efficiency and ensures adequate protection against freezing of the condensate pan and the resulting potential overflow.

[0016] The run-on time defines the duration for which the condensate pan heater should continue heating after the evaporator has defrosted. The goal is to give the condensate time to completely drain from the condensate pan.

[0017] Obtaining the run-on time includes receiving and evaluating a data stream containing information regarding the run-on time, obtaining a value for the run-on time through an input, in particular a user input, but also determining the run-on time using sensors and corresponding evaluation electronics.

[0018] In particular, when determining the run-on time, other parameters such as an outside temperature at the evaporator are also taken into account.

[0019] For example, if the specified run-on time is five minutes, the condensate pan heater heats the condensate pan for a period of five minutes after the evaporator defrosting process has been completed by the control electronics.

[0020] The condensate falls mainly during the defrosting process on the evaporator.

[0021] In an advantageous embodiment of an aspect of the invention, the follow-up time is an adjustable multiple of the duration of the defrosting process.

[0022] In this case, the duration of the defrosting process is determined by a setting. In particular, this setting is an input, for example, a user input. The duration of the defrosting process is, in particular, only the time the compressor is running.

[0023] If this adjustable multiple is, for example, 0.2, this means that the run-on time is 20% of the duration of the defrosting process.

[0024] The design of the run-on time as an adjustable multiple of the duration of the defrosting process enables simple and efficient operation, since the duration of the defrosting process correlates with the amount of falling condensate and thus the run-on time varies according to the amount of falling condensate.

[0025] In an alternative advantageous embodiment of an aspect of the invention, the follow-up time comprises an adjustable multiple of the duration of the defrosting process and a duration of an intensive defrosting.

[0026] Intensive defrosting follows a normal defrosting process and is performed regularly, especially to defrost the heat pump's air ducts. This increases the heat pump's operational reliability.

[0027] It is advantageous to operate the condensate pan heating in parallel with the intensive defrosting, since condensate can also fall off the evaporator during the intensive defrosting.

[0028] In a further advantageous embodiment of an aspect of the invention, the defrosting process of the evaporator includes a compressor downtime.

[0029] In a further advantageous embodiment of an aspect of the invention, the method according to the invention comprises the following steps: obtaining an outside temperature at the evaporator, heating the condensate tray by the condensate tray heater as a function of the outside temperature.

[0030] Obtaining the outside temperature involves, among other things, measuring the outside temperature, but also receiving and evaluating a data stream containing information about the outside temperature. Heating the condensate pan by the condensate pan heater depending on the outside temperature means that the control electronics initiates or stops heating the condensate pan by the condensate pan heater based on information about the outside temperature.

[0031] The outside temperature is preferably the temperature of outside air, the energy of which is used by an air-water heat pump to evaporate a refrigerant from the liquid phase to the gaseous phase in a cycle in the heat exchanger.

[0032] In a further advantageous embodiment of an aspect of the invention, the method according to the invention comprises the following step: heating the condensate tray by the condensate tray heater when the outside temperature at the evaporator falls below a predefined threshold value, in particular 2 °C.

[0033] The predefined threshold can vary depending on tolerances, such as the accuracy of the outside temperature determination. For example, it is also possible to set the predefined threshold as 1.5 °C or 1 °C. In any case, for efficiency reasons, it has proven advantageous not to set the value to a temperature greater than 2 °C.

[0034] This enables particularly efficient operation, as at outside temperatures above the predefined threshold, any ice in the condensate tray melts due to the temperature of the air in the condensate tray. Heating the condensate tray is therefore not necessary at outside temperatures above the predefined threshold. The outside temperature condition prevents unnecessary operation of the condensate tray heating.

[0035] In particular, the setting of the predefined threshold is an input, for example, a user input. This can increase operational reliability under critical operating conditions.

[0036] For the condensate pan to be heated by the condensate pan heater, two conditions must be met: First, the evaporator defrosting process must be underway. Second, the outside temperature at the evaporator must be below a predefined threshold.

[0037] In a further advantageous embodiment of an aspect of the invention, the heat pump comprises a drain pipe and a pipe trace heater which is designed to heat the drain pipe, and the method according to the invention comprises the following steps: heating the drain pipe by the pipe trace heater when the defrosting process of the evaporator is started by the control electronics, ending the heating of the drain pipe by the pipe trace heater when the defrosting process of the evaporator is ended by the control electronics, or ending the heating of the drain pipe by the pipe trace heater after the defrosting process of the evaporator is ended by the control electronics and expiry of the follow-up time which begins to run when the defrosting process of the evaporator is ended by the control electronics.

[0038] Preferably, the control electronics controls the pipe trace heating. Such control includes starting and stopping heating by the pipe trace heating.

[0039] The pipe trace heating is installed in the drainpipe, which is connected to a drain of the condensate tray. This drain is, for example, a drain socket. The drainpipe with pipe trace heating is specifically designed as a high-temperature pipe (HT pipe). The drain socket allows the drainpipe to be connected and the condensate to be directed into the stormwater drain or, alternatively, to allow the water to seep into a gravel bed below the frost line.

[0040] The pipe trace heating can be a standalone heating cable or part of the condensate pan heating.

[0041] To ensure that the condensate can flow smoothly down the drain pipe below the frost line, a retrofittable electric pipe heating system is particularly advantageous as part of the heat pump's accessories. When installed on a floor-standing or wall bracket, pipe heating is recommended, regardless of the type of condensate pan heating, as the drain pipe is directly exposed to the ambient air in these installations.

[0042] When heating the condensate pan, simultaneous pipe trace heating is advantageous, as it offers economic and technical advantages through synergy effects. Both heaters are controlled simultaneously, resulting in potential savings on a relay and lower procurement costs for a single heating system instead of two separate ones.

[0043] In a further advantageous embodiment of an aspect of the invention, the heat pump comprises a drain pipe and a pipe trace heating system which is designed to heat the drain pipe, and the method according to the invention comprises the following steps: obtaining an outside temperature at the evaporator, heating the drain pipe by the pipe trace heating system only when the outside temperature at the evaporator falls below a predefined threshold value, in particular 2 °C, particularly preferably 1 °C.

[0044] This means that the pipe trace heating can also be operated permanently below the predefined threshold for the outside temperature and only the condensate pan heating is controlled depending on the defrosting process and in particular the outside temperature.

[0045] This enables particularly efficient operation, as at outside temperatures above the predefined threshold, any ice in the condensate tray melts due to the temperature of the air in the condensate tray. Heating the drain pipe is therefore not absolutely necessary at outside temperatures above the predefined threshold. The outside temperature condition prevents unnecessary operation of the pipe trace heating system.

[0046] In particular, the setting of the predefined threshold is an input, for example, a user input. This can increase operational reliability under critical operating conditions.

[0047] According to a further aspect of the invention, this object is achieved by a heat pump comprising control electronics, an evaporator, a condensate pan, a condensate pan heater, wherein the condensate pan is designed to collect condensate falling on the evaporator, wherein the control electronics is designed to start and end a defrosting process of the evaporator, wherein the control electronics is designed to control the condensate pan heater, wherein the control electronics is designed to control the condensate pan heater such that the condensate pan heater heats the condensate pan during the defrosting process and only heats it for the duration of a follow-up time after the defrosting process has ended.

[0048] A heat pump according to the invention is in particular an air-water heat pump.

[0049] Air-to-water heat pumps utilize the ambient energy of the outside air to evaporate a refrigerant from the liquid phase to the gaseous phase in a circular process within the heat exchanger. The refrigerant in the evaporator is therefore several degrees cooler than the ambient air, allowing it to transfer evaporation energy from it. The refrigerant is then brought to a higher pressure and temperature level by an electrically driven compressor, allowing it to be used in the condenser to release heat and heat a building and / or provide hot water.

[0050] The outdoor evaporator becomes significantly colder than the ambient temperature during operation, which is why it is very easy for the temperature to fall below the dew point. This lowering of the dew point causes the air at the evaporator to become saturated. As a result, the humidity collects on the evaporator as condensate. At temperatures significantly above freezing, the condensate collects and drips off the evaporator. At low outside temperatures, when the refrigerant evaporates below 0°C, the condensate freezes on the evaporator, forming an insulating layer of ice that impedes heat exchange in the refrigeration cycle and impedes airflow through the evaporator. When and how quickly the evaporator freezes depends largely on the outside temperature and humidity.

[0051] Two options are available for detecting frost in the evaporator. In units with radial fans, the increasing differential pressure between the evaporator inlet and outlet as frost builds up can be used to determine whether the evaporator is frozen. At a certain predefined pressure threshold, the evaporator is detected as frozen, and the defrosting process is initiated. Because units with axial fans, due to their design, develop lower pressure differences, reliable conclusions about frost formation cannot be drawn based on the differential pressure due to external interference.

[0052] In the second variant, the evaporation temperature is measured. This decreases with increasing icing due to poorer heat transfer. A reference temperature is measured shortly after the heat pump is switched on or shortly after a defrosting process. At this value, the evaporator is assumed to be free of ice. With this method, the defrosting process is also initiated when a certain difference threshold is reached.

[0053] As soon as the control electronics detects that the evaporator is iced up using one of the methods described above, the defrosting process is initiated. The reversing cooling circuit method has proven particularly popular over other defrosting methods. With reversing the cooling circuit, the cooling circuit is briefly reversed via a 4 / 2-way valve, allowing the heat from the heating system to defrost the evaporator.

[0054] In an advantageous embodiment of an aspect of the invention, the follow-up time is an adjustable multiple of the duration of the defrosting process.

[0055] In a further advantageous embodiment of an aspect of the invention, the condensate pan heater of the heat pump is an electrical condensate pan heater, in particular a self-regulating heating cable or a heating mat.

[0056] In principle, various solutions are available for electrically operated resistance heating systems. These include tubular heaters, bare wire heating elements, self-regulating heating cables, and fixed resistance heating cables. The latter two options are more suitable for use in ice removal, as the former are used primarily in building services for hot water and space heating where high performance requirements are required.

[0057] Self-regulating heating cables have a high positive temperature coefficient, which allows them to reduce their output even as the temperature rises. On the other hand, fixed resistance heating cables can be used, which have a nearly constant resistance over a wide temperature range.

[0058] The heating cable is permanently connected to the low-voltage supply network between a phase conductor and the neutral conductor, resulting in a fixed operating voltage of 230 V. Power modulation via pulsed supply voltage is not performed to protect the relay.

[0059] In one embodiment, the condensate tray is an aluminum tray into which a self-adhesive heating mat is attached. In another embodiment, a self-regulating heating cable, which is placed in an insulating mat with recesses for this purpose, is installed in an aluminum tray for heating. In other embodiments, a plastic tray or a tray made of foams such as expanded polystyrene (EPS) or expanded polypropylene (EPP) can be used instead of the aluminum tray.

[0060] The different designs, for example the aluminum tray with heating mat and / or the plastic tray with heating cable, have their own advantages and disadvantages. The design consisting of an aluminum tray and heating mat offers an elegant solution for keeping the condensate tray free of ice without having to have a heater in the tray itself. From a manufacturing perspective, the heating mat is also easy to process, as the precisely fitting mat only needs to be glued to the tray in one uncomplicated step, unlike the design with the plastic tray and heating cable. Here, the cable has to be laid in the designated guides, which is comparatively laborious and takes more time. However, the direct heating in the plastic tray and the slightly thermally insulating properties of the plastic tray can reduce power consumption slightly.The disadvantages are the larger bending radii of the self-limiting heating cable, which results in a more uneven heat distribution, and the higher inrush currents, which means that the relay used ages faster and has to be dimensioned larger.

[0061] However, the material of the condensate pan is not limited to aluminum and plastic. Likewise, the condensate pan heating is not limited to a heating cable or a heating mat. The invention is also not limited to the described examples, but encompasses any conceivable combination of a condensate pan and a condensate pan heating system, regardless of the material of the condensate pan and the type of condensate pan heating system.

[0062] In a further advantageous embodiment of an aspect of the invention, the defrosting process of the evaporator includes a compressor downtime.

[0063] The compressor downtime consists in particular of a duration, in particular 10 to 60 seconds, before the reversal of the refrigeration circuit via a changeover valve, for example a 4 / 2-way valve, and a duration, in particular 1 to 2 minutes, after the reversal of the refrigeration circuit.

[0064] This compressor downtime allows, in particular, the compressor to run down and to avoid negative effects on the compressor of heat pipe effects caused by refrigerant displacement and / or pressure differences occurring during the reversal of the refrigeration circuit.

[0065] The compressor downtime is mainly based on the valve operating times of the hydraulic system.

[0066] A compressor downtime contributes to increasing the efficiency of the heat pump.

[0067] In a further advantageous embodiment of an aspect of the invention, the control electronics controls the condensate pan heating depending on an outside temperature surrounding the evaporator.

[0068] A simple but effective way to control the condensate pan heating is to use the evaporator defrost signal in conjunction with the measured outside temperature as the start condition for a heating cycle.

[0069] In a preferred variant of the above embodiment, the condensate pan heater heats the condensate pan only when the outside temperature at the evaporator falls below a predefined threshold value, in particular 2 °C, particularly preferably 1 °C.

[0070] At low outside temperatures, when the refrigerant evaporates below 0 °C, the condensate freezes on the evaporator and forms an insulating layer of ice, which hinders the heat exchange in the refrigeration cycle and the airflow through the evaporator.

[0071] It is therefore advantageous to heat the condensate tray in parallel with the evaporator defrosting when the outside temperature is below 2 °C.

[0072] This feature therefore represents an additional condition that must be verified before the condensate pan is heated in order to initiate the heating process of the condensate pan heater. The evaporator defrost condition has been started, and the outside temperature at the evaporator falls below a predefined threshold, specifically 2 °C, must both be met for the condensate pan heater to start heating the condensate pan. This enables particularly economical and efficient operation.

[0073] In a further advantageous embodiment of an aspect of the invention, the heat pump comprises a drain pipe, attached to an outlet of the condensate pan, a pipe trace heating system which is designed to heat the drain pipe, wherein the pipe trace heating system is controlled by the control electronics and the control electronics controls the pipe trace heating system such that the pipe trace heating system heats the drain pipe when the condensate pan heating system heats the condensate pan, and / or wherein the pipe trace heating system is controlled by the control electronics as a function of an outside temperature surrounding the evaporator and the control electronics controls the pipe trace heating system such that the pipe trace heating system only heats the drain pipe when the outside temperature at the evaporator falls below a predefined threshold value, in particular 2 °C, particularly preferably 1 °C.

[0074] The drain is specifically designed as a drain socket. The drain pipe with trace heating is specifically a high-temperature pipe (HT pipe). The drain socket allows the drain pipe to be connected and the condensate to be directed into the stormwater drain or, alternatively, to allow the water to seep into a gravel bed below the frost line.

[0075] To ensure that the condensate can flow smoothly down the drain pipe below the frost line, a retrofittable electric pipe heating system is particularly advantageous as part of the heat pump's accessories. When installed on a floor-standing or wall bracket, pipe heating is recommended regardless of the type of condensate pan heating, as the drain pipe is directly exposed to the ambient air in these installations.

[0076] When heating the condensate pan, simultaneous pipe trace heating is advantageous, as it offers economic and technical advantages through synergy effects. Both heating systems are controlled simultaneously, resulting in a potential savings on a relay and lower procurement costs for a single heating system instead of two separate ones.

[0077] Alternatively, it is also possible to operate the pipe trace heating permanently below the predefined threshold for the outside temperature and to only control the condensate pan heating depending on the defrosting process and in particular the outside temperature.

[0078] In a further advantageous embodiment of an aspect of the invention, the heat pump comprises at least one sensor, an evaluation electronics for the at least one sensor, designed to detect whether there is ice or water in the condensate tray, wherein the at least one sensor and the evaluation electronics are arranged on a circuit board which is designed to be mountable in the condensate tray.

[0079] This sensor technology has the potential to increase efficiency in the condensate pan heating system. The increased efficiency is based on a sensor that detects whether there is actually ice in the pan and therefore a defrosting requirement. This prevents unnecessary operation when there is no ice in the pan.

[0080] The dielectric properties of ice and water depend on the temperature and frequency of the exciting electric field. This is modeled by the complex relative permittivity. The complex-valued relative permittivity arises because the molecular dipoles cannot instantly follow the exciting electric field at higher frequencies, resulting in a phase shift between the field and the dipoles. This property can be exploited in practice by measuring and comparing the capacitance at different frequencies. Thus, for example, using a circuit board and a variable-frequency capacitance meter, it is possible to reliably detect whether ice, water, or air is present on a sensor.

[0081] An external sensor board is not particularly suitable for use in heat pumps, as a coaxial cable would potentially have to be routed across the device from the control board to the sensor, which would expose it to various sources of interference, such as frequency converters. Furthermore, the coaxial cable carries a parasitic capacitance, which, even for short cable lengths, is on the order of magnitude of the actual capacitance being measured. For example, with commercially available RG 58 coaxial cables, the capacitance per unit length can be up to 100 pF / m. The capacitance of a sensor, even in dry conditions, is a few tens of pF.

[0082] Instead, an electronic assembly is developed as a practical example with a sensor and evaluation electronics on a single circuit board, so that only a power supply and a communication interface to the control board need to be installed. To avoid complex impedance measurements, the capacitance is determined using a repeated charge transfer method.

[0083] An example circuit diagram for measuring an unknown capacitance at different frequencies is shown in Fig. 5. CX1 represents the unknown capacitance of a conductor arrangement. This capacitance is applied to the reference voltage U via an N-channel metal-oxide-semiconductor field-effect transistor (MOSFET) VF1 Refof 1.8 V. The BSS138BK type was chosen for all three MOSFETs VF1, VF2, and VF3 because of its low gate-source threshold voltage of 1.1 V and fast rise (5 ns) and fall (20 ns) times. However, other MOSFET types are also suitable. VF1 is then turned off, and the charge Q is transferred to the reference capacitor C9.

[0084] Capacitor C9 is sized at 2.2 nF, approximately three orders of magnitude larger than the capacitance to be measured. This difference in size allows us to assume, with a good approximation, that the entire charge Q from CX1 to C9 has been transferred. If VF2 is now blocked again, a new charge and charge transfer cycle can be started. These cycles are repeated n times at a frequency defined by the software to generate a voltage at C9 that is easy to measure.

[0085] This voltage is sensed at the non-inverting input of operational amplifier N3 and, thanks to the wiring of R1 and R2, amplified in a non-inverting manner, allowing this amplified voltage to be measured non-interferingly by the STM32 microcontroller. The microcontroller is also responsible for switching the MOSFETs. A Texas Instruments OPA365 was chosen for the operational amplifier because of its low input bias current (±10 pA) and the ability to operate from a single voltage rail. However, other operational amplifiers are also conceivable. A low input bias current is important, as otherwise the voltage at C9 would be excessively influenced by the continuous addition or removal of charge.

[0086] Before each charging cycle, VF3 is briefly activated, discharging the reference capacitor C9. With the voltage U finally applied to C9 Mess, can be calculated back to CX1 using the following formula, since C9, n, and U Ref are known. CX1=C9⋅UMessn⋅URef

[0087] From the STM32 family, the STM32L496VET6 was chosen in particular. With its 12-bit analog-to-digital converter (ADC), it is particularly well-suited for precise voltage measurement. However, other microcontrollers can also be used, especially microcontrollers with a smaller number of general-purpose input / output (GPIO) pins. With its 83 GPIO pins, the STM32L496VET6 is significantly oversized for this application, as three GPIO pins and one ADC input are sufficient for the task. For use in the heat pump, an additional communication interface must be provided from the microcontroller.

[0088] Despite the reference function of C9, a simple X7R ceramic capacitor with a high tolerance of 10% is used, since only the relationship between two measured values ​​is relevant in the described method. Both measurements are performed with the same reference capacitor, which reduces the deviation due to tolerance when calculating the quotient.

[0089] The circuit board comprising the sensor and evaluation electronics is designed in particular so that it can be mounted in the condensate tray without changing the dimensions of the condensate tray. A condensate tray with an integrated circuit board comprising the sensor and evaluation electronics therefore preferably requires no more space in the heat pump than a condensate tray without a circuit board.

[0090] In an advantageous embodiment, the condensate tray is heated by the condensate tray heater depending on whether the sensor detects ice in the condensate tray.

[0091] In the following, the present invention is further illustrated and explained with reference to exemplary embodiments shown in the figures. Fig. 1 in a schematic representation to illustrate an embodiment, a bottom view of a subfloor of a heat pump with condensate tray, Fig. 2 in a further schematic representation to illustrate the embodiment, a top view of the underbody of the heat pump with condensate tray, Fig. 3 in a further schematic representation to illustrate the embodiment, a further plan view of the underbody of the heat pump with condensate tray, Fig. 4 in a further schematic representation to illustrate the embodiment, a plan view of the underbody of the heat pump with condensate tray in a different perspective, Fig. 5 a schematic representation to illustrate an embodiment of a circuit diagram, Fig. 6 a schematic diagram illustrating an embodiment of a circuit board, Fig. 7 a flowchart of a method according to the invention.

[0092] Fig. Figure 1 shows a schematic diagram illustrating an embodiment of a heat pump subfloor 1. A condensate tray 2 is mounted in this subfloor 1. The condensate tray is removably secured to the heat pump, particularly via positioning geometries or locking elements and fastening elements such as screws. "Removable" means that the condensate tray 2 can be removed again without damaging or destroying the condensate tray 2, the heat pump, or the fastening elements.

[0093] Condensate tray 2 is located below the evaporator and collects the condensate falling from the heat pump's evaporator. This condensate is collected in the condensate tray 2 and drained out of the heat pump via drain 4.

[0094] To prevent ice formation, the condensate tray 2 has a condensate tray heater 3. This is mounted within the condensate tray 2, in particular in a heater receptacle in the condensate tray 2. This heater receptacle is, for example, a recess in the condensate tray 2, in which the condensate tray heater 3 is inserted and secured. The drain 4 is in Fig. 1 is designed as a drain connection. This allows a pipe to be attached to drain 4 to conduct the condensate. This pipe is, in particular, an HT pipe with pipe trace heating.

[0095] Fig. 2 and Fig. 3 show in a schematic representation to illustrate the embodiment a plan view of the subfloor 1 of a heat pump from Fig. 1. A strainer 5 is indicated above the drain 4. This strainer 5 prevents the drain 4 of the condensate tray 2 from becoming clogged by preventing debris, such as leaves, that has accumulated in the condensate tray 2 and is carried by the condensate to the drain 4 from entering the drain and accumulating there.

[0096] In this embodiment, the condensate pan heating 3 is implemented by an electric heating strip, which is threaded into guides in the condensate pan 2 and held in place by locking tabs 6. During installation of the pan, the electrical connection of the heating strip in the heat pump is connected to the electrical supply.

[0097] The guide is designed as a heating element and runs in Fig. 2 and Fig. 3 as a bulge of the condensate tray 2 with three loops through the condensate tray 2. However, the invention is not limited to this embodiment, but encompasses any desired course of the guide in the condensate tray 2. Preferred are courses of the guide which cover as large a part of the surface of the condensate tray as possible and not, for example, only run along one side of the condensate tray 2.

[0098] The condensate tray 2 also has a sloping bottom surface towards the drain 4.

[0099] The condensate pan 2 is suspended below the evaporator using a locking mechanism or positioning geometry and then secured with fasteners such as heat pump screws. The mounting recesses of the condensate pan 2 provided for the fastening elements are located opposite the locking mechanism or positioning geometry. The recess can be realized in the condensate pan 2 itself or through additional components, such as press-in nuts. To remove the condensate pan 2, the electrical connection of the heating strip is disconnected. The fastening elements are then loosened and the condensate pan 2 is pushed out of the locking mechanism or positioning geometry.

[0100] Fig. 4 shows the second embodiment from the Fig. 2 and Fig. 3 in a different perspective. In addition to the condensate tray 2, the condensate tray heater 3 located therein, and the strainer 5, the drain 4 is also clearly visible in this view.

[0101] Fig. 5 shows a circuit diagram for a sensor and evaluation electronics for the sensor, designed to detect whether there is ice or water in the condensate tray. Fig. 5 has already been explained, which is why it is referred to here to avoid redundancy.

[0102] Fig. 6 shows an embodiment of a circuit board 90 comprising a sensor surface 91, which in Fig. 6 already includes a sensor. Alternatively, the sensor surface 91 can also be designed to accommodate a corresponding sensor and connect it to the circuitry of the circuit board 90. Additionally, evaluation electronics 92 for the sensor 91 are mounted on the circuit board 90.

[0103] Fig. 6 shows a top side of the board 90, marked with “Top Layer” and a bottom side of the board 90, marked with “Bottom Layer”.

[0104] The evaluation electronics 92 are predominantly mounted on the top side of the circuit board 90, while the sensor surface 91 and thus the sensor are formed on the underside of the circuit board 90. Such an advantageous arrangement protects the evaluation electronics 92 from moisture, but does not limit the sensor's accuracy. The circuit board 90 is mounted with its top side on a side wall of the condensate tray 1, so that the evaluation electronics are arranged towards the side wall and the sensor surface 91 faces the interior of the condensate tray. This ensures that the presence of ice in the condensate tray can be detected on the sensor surface 91. For additional protection of the evaluation electronics 92, it is in particular coated with a protective layer or encased in a housing.

[0105] However, the invention is not limited to such an arrangement, but encompasses any possible arrangement of sensor surface 91 and evaluation electronics 92 on the circuit board 90, for example also an arrangement in which sensor surface 91 and evaluation electronics 92 are arranged on the same side of the circuit board 90.

[0106] Fig. Figure 7 shows a schematic representation of a method according to the invention. In a first step S101, a run-on time of the condensate pan heater 3 is determined.

[0107] In a further step S102, the condensate tray 2 is heated by the condensate tray heater 3 when the defrosting process of the evaporator starts.

[0108] Finally, in a further step S103, the heating of the condensate pan 2 by the condensate pan heater 3 is terminated after the evaporator defrosting process has been completed by the control electronics and the run-on time, which begins when the evaporator defrosting process is completed by the control electronics, has elapsed. Thus, the condensate pan heater 3 is only used when the evaporator defrosting process requires it. List of reference symbols 1 Underbody of a heat pump 2 condensate tray 3 Condensate pan heating 4 Drain 5 Sieve 6 locking lug 90 board 91 sensor area 92 Evaluation electronics

Claims

[1] Method for heating a condensate tray (2) of a heat pump, wherein the heat pump comprises an evaporator and a condensate tray heater (3) and the condensate tray (2) is designed to collect condensate falling at the evaporator, the method comprising the following steps: Erlangen (S101) a run-on time of the condensate pan heating (3), Heating (S102) of the condensate tray (2) by the condensate tray heater (3) when the evaporator defrosting process starts, Termination (S103) of the heating of the condensate tray (2) by the condensate tray heater (3) after completion of the defrosting process of the evaporator by the control electronics and expiration of the follow-up time, which begins to run when the defrosting process of the evaporator by the control electronics is completed. [2] Method according to claim 1, wherein the follow-up time is an adjustable multiple of the duration of the defrosting process. [3] Method according to claim 1, wherein the follow-up time comprises an adjustable multiple of the duration of the defrosting process and a duration of an intensive defrosting. [4] Method according to one of the preceding claims, wherein the defrosting process of the evaporator comprises a compressor downtime. [5] Method according to one of the preceding claims, comprising the following steps: Achieving an outside temperature at the evaporator, Heating of the condensate tray (2) by the condensate tray heater (3) depending on the outside temperature. [6] A method according to claim 5, comprising the following step: Heating of the condensate tray (2) by the condensate tray heater (3) only when the outside temperature at the evaporator falls below a predefined threshold, in particular 2 °C, particularly preferably 1 °C. [7] Method according to one of the preceding claims, wherein the heat pump comprises a drain pipe and a pipe trace heating system which is designed to heat the drain pipe, comprising the following steps: Heating of the drain pipe by the pipe trace heating when the defrosting process of the evaporator is started by the control electronics, Termination of heating of the drain pipe by the pipe trace heating when the defrosting process of the evaporator is terminated by the control electronics, or Termination of the heating of the drain pipe by the pipe trace heating after completion of the defrosting process of the evaporator by the control electronics and expiration of the run-on time, which begins to run when the defrosting process of the evaporator by the control electronics is completed. [8] Method according to one of claims 1 to 7, wherein the heat pump comprises a drain pipe and a pipe trace heating system designed to heat the drain pipe, comprising the following steps: Achieving an outside temperature at the evaporator, Heating of the drain pipe by the pipe trace heating only when the outside temperature at the evaporator falls below a predefined threshold, in particular 2 °C, particularly preferably 1 °C. [9] Heat pump comprehensive control electronics, an evaporator, a condensate tray (2), a condensate pan heater (3), wherein the condensate tray (2) is designed to collect condensate falling from the evaporator, wherein the control electronics are designed to start and stop a defrosting process for defrosting the evaporator, wherein the control electronics are designed to control the condensate pan heating (3), wherein the control electronics are designed to control the condensate pan heating (3) in such a way that the condensate pan heating (3) heats the condensate pan (2) during the defrosting process and, after the defrosting process has ended, heats it only for the duration of a follow-up time. [10] Heat pump according to claim 9, wherein the run-on time is an adjustable multiple of the duration of the defrosting process. [11] Heat pump according to one of claims 9 and 10, wherein the condensate pan heater (3) is an electrical condensate pan heater (3), in particular a self-regulating heating cable or a heating mat. [12] Heat pump according to one of claims 9 to 11, wherein the defrosting process of the evaporator includes a compressor downtime. [13] Heat pump according to one of claims 9 to 12, wherein the control electronics controls the condensate pan heating (3) depending on an outside temperature surrounding the evaporator. [14] Heat pump according to claim 13, wherein the condensate pan heater (3) heats the condensate pan (2) only if, in addition, the outside temperature at the evaporator falls below a predefined threshold value, in particular 2 °C. [15] Heat pump according to one of claims 9 to 14, comprising a drain pipe attached to a drain of the condensate tray, a pipe trace heating system designed to heat the drain pipe, wherein the pipe trace heating system is controlled by the control electronics and the control electronics controls the pipe trace heating system such that the pipe trace heating system heats the drain pipe when the condensate pan heating system (3) heats the condensate pan (2), and / or wherein the pipe trace heating is controlled by the control electronics depending on an outside temperature surrounding the evaporator and the control electronics controls the pipe trace heating in such a way that the pipe trace heating heats the drain pipe when the outside temperature at the evaporator falls below a predefined threshold value, in particular 2 °C, particularly preferably 1 °C. [16] Heat pump according to one of claims 9 to 15, comprising at least one sensor, an evaluation electronics (92) for the at least one sensor, designed to detect whether there is ice or water in the condensate tray (2), wherein the at least one sensor and the evaluation electronics (92) are arranged on a circuit board (90) which is designed to be mountable in the condensate tray (2).

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