Heat pump water heaters and their control methods

Abstract

This invention provides a heat pump water heater and its control method. The heat pump water heater includes a heat pump main unit, a buffer tank, and a coil connected to the inlet and outlet of the heat pump main unit and disposed within the buffer tank. The heat pump main unit includes a controller. A first temperature sensor is installed on the coil, and a second temperature sensor is installed in the buffer tank. The controller is connected to both the first and second temperature sensors. The controller acquires a first temperature difference ΔT1 between the coil temperature T1 measured by the first temperature sensor and the buffer tank temperature T2 measured by the second temperature sensor. When the first temperature difference ΔT1 exceeds a set temperature difference threshold, the controller reduces the operating frequency f of the compressor in the heat pump main unit. Compared with existing technologies, this invention prevents overheating of the heat pump main unit by determining whether the failure of the current water temperature in the tank to reach the target value is due to low heat exchange efficiency of the coil caused by scale buildup in the heating element.

Description

Technical Field

[0001] This invention relates to the field of heat pump water heaters, and in particular to a control method, controller, and heat pump water heater for a heat pump water heater. Background Technology

[0002] Compared to ordinary electric water heaters, heat pump water heaters have the advantages of energy saving and environmental protection. With energy conservation and environmental protection becoming increasingly important, the use of heat pump water heaters is becoming more and more widespread. Figure 1 As shown, a conventional heat pump water heater includes a heat pump unit 10, a buffer tank 20, and a coil 30 installed inside the buffer tank. The heat pump unit 10 has a heat pump outlet 11 and a heat pump inlet 12, the coil 30 has a coil inlet 31 and a coil outlet 32, and the buffer tank 20 has a buffer tank inlet 21 and a buffer tank outlet 22. The heat pump outlet 11 is connected to the coil inlet 32, and the heat pump outlet 12 is connected to the coil inlet 21 to form a loop. Water flowing from the coil outlet 32 ​​passes through the heat pump inlet. Water flows into the condenser of the heat pump unit 10 through the condenser. After the condenser heats the water, it enters the coil 30 through the heat pump outlet 11 and the coil inlet 32. The hot water in the coil 30 transfers heat to the water in the buffer tank 20, heating the water in the buffer tank. Then, the water in the coil 30 flows back to the condenser of the heat pump unit 10 through the coil outlet 31 and the heat pump inlet 12. The heated water in the buffer tank 20 can flow out through the buffer tank outlet 21 for daily use, while the buffer tank inlet 22 is used to replenish cold water into the buffer tank 20.

[0003] However, the efficiency of heat pump water heating is also affected by many factors. For example, scale will be generated in the coil 30 during long-term use. The scale will accumulate on the surface of the coil 30, resulting in a decrease in the heat exchange efficiency of the coil 30. In this case, in order to heat the water in the buffer tank 20 to the set target temperature, it is necessary to increase the compressor frequency of the heat pump host 10 so that the water temperature delivered by the heat pump host 10 to the coil 30 is increased. However, excessively high water temperature often causes the heat pump host 10 to trigger overheat protection before the water in the buffer tank 20 is heated to the set target temperature, thereby causing the compressor of the heat pump host 10 to stop running, and the water in the buffer tank 20 cannot be heated to the set target temperature. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a heat pump water heater that can prevent the heat pump unit from overheating and a control method for the heat pump water heater.

[0005] The heat pump water heater provided by the present invention includes a heat pump main unit, a buffer water tank, and a coil connected to the inlet and outlet of the heat pump main unit and disposed in the buffer water tank. The heat pump main unit includes a controller. The coil is provided with a first temperature sensor, and the buffer water tank is provided with a second temperature sensor. The controller is connected to the first temperature sensor and the second temperature sensor respectively. The controller is used to obtain a first temperature difference ΔT1 between the coil temperature T1 measured by the first temperature sensor and the buffer water tank temperature T2 measured by the second temperature sensor. When the first temperature difference ΔT exceeds a set temperature difference threshold, the controller reduces the operating frequency f of the compressor of the heat pump main unit.

[0006] Furthermore, it also includes an ambient temperature sensor, which is connected to the controller; the controller is also used to acquire the ambient temperature T, the compressor operating frequency f, and the heat exchange status value of the heat pump host, and to determine whether the heat exchange status value is within the range of the heat exchange status threshold corresponding to the ambient temperature T and the operating frequency f. If so, and the first temperature difference ΔT1 exceeds the set temperature difference threshold, then the operating frequency f of the compressor is reduced.

[0007] Furthermore, it also includes a third temperature sensor located at the outlet of the heat pump unit, a fourth temperature sensor located at the inlet of the heat pump unit, and / or a fifth temperature sensor located on the condenser of the heat pump unit; the heat exchange status value of the heat pump unit obtained by the controller includes a second temperature difference ΔT2 between the heat pump outlet water temperature T3 measured by the third temperature sensor and the heat pump inlet water temperature T4 measured by the fourth temperature sensor, and / or, the heat exchange status value of the heat pump unit obtained by the controller includes a third temperature difference ΔT3 between the heat pump outlet water temperature T3 measured by the third temperature sensor and the condensation temperature T5 measured by the fifth temperature sensor.

[0008] Furthermore, the controller is also used to shut down the heat pump host when the heat pump outlet water temperature T3 reaches the set first temperature protection threshold Tx1, and to restart the heat pump host after the heat pump inlet water temperature T4 drops to less than or equal to the buffer water tank temperature T2.

[0009] Furthermore, the controller is also used to shut down the heat pump host when the outlet water temperature T3 reaches the set second temperature protection threshold Tx2, and to restart the heat pump host after the heat pump host has been shut down for a set shutdown time, and to make the compressor of the heat pump host run at the lowest operating frequency.

[0010] Furthermore, when the first temperature difference ΔT1 exceeds the set temperature difference threshold, the larger the first temperature difference ΔT1 is, the greater the reduction in the operating frequency f of the compressor of the heat pump host.

[0011] Furthermore, the controller is also used for:

[0012] When the preset first temperature threshold X1 < the first temperature difference ΔT1 < the preset second temperature threshold X2, the compressor frequency f is reduced by a preset first adjustment amount Δf1.

[0013] When the preset second temperature threshold X2 < the first temperature difference △T1 < the preset third temperature threshold X3, the compressor frequency f is reduced by a preset second adjustment amount △f2.

[0014] When the first temperature difference ΔT1 is greater than the preset third temperature threshold X3, the compressor frequency f is reduced by the preset third adjustment amount Δf3.

[0015] Wherein, the first temperature threshold X1 < the second temperature threshold X2 < the third temperature threshold X3, and the first adjustment amount △f1 < the second adjustment amount △f2 < the third adjustment amount △f3.

[0016] Furthermore, the controller is also used to acquire the buffer tank temperature T2 and the compressor operating frequency f again after the compressor frequency f decreases. If the buffer tank temperature T2 is lower than the set target temperature T0 and the compressor frequency f has not decreased to the minimum operating frequency, the first temperature difference ΔT1 is acquired again. When the first temperature difference ΔT1 exceeds the set temperature difference threshold, the controller reduces the operating frequency f of the compressor of the heat pump host again.

[0017] Furthermore, the controller is also used to adjust the compressor operating frequency f after the compressor has been running at a state less than the minimum oil return frequency for a set first operating time, so that the compressor runs at the minimum oil return frequency for a set second operating time.

[0018] On the other hand, the present invention provides a control method for a heat pump water heater. The heat pump water heater controlled by the method includes a heat pump main unit, a buffer tank, and a coil connected to the inlet and outlet of the heat pump main unit and disposed in the buffer tank. The method includes the following steps:

[0019] S102: Obtain the first temperature difference ΔT1 between the coil temperature T1 and the water tank temperature T2;

[0020] S103: If the first temperature difference △T1 exceeds the set temperature difference threshold, reduce the compressor's operating frequency f.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. By checking whether the temperature difference between the coil temperature and the buffer tank temperature exceeds the set temperature difference threshold, it can be determined whether the failure of the current tank water temperature to reach the target value is due to low heat exchange efficiency of the heating element caused by scale buildup. If so, the operating frequency of the compressor is reduced to lower the outlet water temperature of the heat pump unit and the water temperature returning to the heat pump unit from the coil, thereby preventing the heat pump unit from overheating.

[0023] 2. By measuring the temperature difference between the inlet and outlet water temperatures of the heat pump unit, as well as the temperature difference between the outlet water temperature and the condensing temperature of the heat pump unit, it can be determined whether the heat pump unit is in normal operating condition, thereby determining whether it is appropriate to adjust the compressor frequency.

[0024] 3. After the heat pump unit shuts down due to overheating, detect the heat pump inlet water temperature and the buffer water tank temperature. Restart the heat pump unit after the heat pump inlet water temperature drops to less than or equal to the buffer water tank temperature to achieve automatic restart after the heat pump unit shuts down due to overheating.

[0025] 4. After the compressor has been running at a frequency lower than the minimum oil return frequency for a set first operating time, adjust the compressor operating frequency f to make the compressor run at the minimum oil return frequency for a set second operating time to prevent excessive wear caused by the compressor running at a frequency lower than the oil return frequency for a long time. Attached Figure Description

[0026] Figure 1 A schematic diagram of the structure of a heat pump water heater in the prior art;

[0027] Figure 2 A flowchart of a control method for a heat pump water heater according to one embodiment of the present invention;

[0028] Figure 3 This is a flowchart of a control method for a heat pump water heater according to one embodiment of the present invention.

[0029] In the diagram: 10, heat pump unit; 11, heat pump outlet; 12, heat pump inlet; 20, buffer tank; 21, buffer tank inlet; 22, buffer tank outlet; 30, coil; 31, coil outlet; 32, coil inlet. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0031] It should be understood that the described embodiments are merely some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of the embodiments of this application.

[0032] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0033] In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0034] Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0035] It should be understood that the embodiments of this application are not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from their scope. The scope of the embodiments of this application is limited only by the appended claims.

[0036] This invention provides a water heater comprising a heat pump unit 10, a buffer tank 20, and a coil 30 connected to the inlet and outlet of the heat pump unit 10 and disposed within the buffer tank 20. The heat pump unit 10 also includes a controller. A first temperature sensor is disposed within the coil 30, and a second temperature sensor is disposed within the buffer tank 20. The controller is connected to both the first and second temperature sensors and is used to acquire a first temperature difference ΔT1 between the coil temperature T1 measured by the first temperature sensor and the buffer tank temperature T2 measured by the second temperature sensor. Specifically, the controller acquires the coil temperature T1 measured by the first temperature sensor and the buffer tank temperature T2 measured by the second temperature sensor, and calculates the first temperature difference ΔT1 between the coil temperature T1 and the buffer tank temperature T2.

[0037] Specifically, the coil temperature T1 can be either the coil inlet water temperature or the coil outlet water temperature. When the coil temperature T1 is the coil outlet water temperature, the first temperature sensor is set at the outlet 31 of the coil 30, and the first temperature difference ΔT1 is the temperature difference between the coil outlet water temperature and the buffer tank temperature T2. After the hot water prepared by the heat pump host 10 passes through the coil 30 and exchanges heat with the water to be heated in the buffer tank 20, the remaining heat of the hot water can be characterized by the first temperature difference ΔT1.

[0038] If the first temperature difference ΔT1 exceeds the set temperature difference threshold, it indicates that the water temperature output from the heat pump unit 10 to the coil 30 is higher than the water temperature in the buffer tank 20. The heat from the water in the coil 30 cannot be fully transferred to the water in the buffer tank 20, resulting in a higher water temperature flowing back from the coil 30 to the heat pump unit 10. This can easily cause the heat pump unit 10 to overheat, triggering its overheat protection. The temperature difference threshold can be set according to the operating performance of the heat pump unit 10 and the coil 30. On one hand, when the first temperature difference ΔT1 exceeds the set threshold, the controller also reduces the operating frequency of the compressor in the heat pump unit 10, thereby reducing the water temperature output from the heat pump unit to the coil 30 and preventing the heat pump unit 10 from triggering overheat protection. On the other hand, if the first temperature difference ΔT1 is too large, it proves that the heat from the heat pump's hot water production has not been fully absorbed by the buffer tank 20. Reducing the operating frequency of the compressor in the heat pump unit 10 also helps improve the energy efficiency of the heat pump unit 10 and reduces unnecessary energy loss.

[0039] Before adjusting the compressor frequency f, it is necessary to determine whether the heat pump unit 10 is in a normal heat exchange state to determine whether it is suitable to adjust the compressor frequency f. For example, adjusting the compressor frequency f when the heat pump unit 10 has just been turned on, such as reducing the compressor frequency f, will result in the water in the buffer tank 20 heating rate being too slow. The heat exchange state of the heat pump unit 10 is affected by the ambient temperature T and the compressor operating frequency f. Under different ambient temperatures T and compressor operating frequencies f, the heat exchange state of the heat pump unit 10 will have certain differences. Therefore, the controller of the heat pump water heater also includes a memory. Before the heat pump water heater leaves the factory, the heat exchange state values ​​of the heat pump unit 10 need to be tested under various different ambient temperatures T and compressor operating frequencies f to obtain the corresponding heat exchange state thresholds as shown in Table 1. The tested different ambient temperatures T, compressor operating frequencies f, and corresponding heat exchange state thresholds are written into the memory so that when the heat pump water heater is actually running, it can determine whether the heat pump unit 10 is in a normal heat exchange state based on the actual measured heat exchange state values ​​and the above data.

[0040]

[0041]

[0042]

[0043] Therefore, in a preferred embodiment, an ambient temperature sensor for detecting ambient temperature T is further included, and the ambient temperature sensor is electrically connected to the controller; the controller is also used to acquire the ambient temperature T, the operating frequency f of the compressor, and the heat exchange status value of the heat pump host 10, and to determine whether the heat exchange status value is within the range of the heat exchange status threshold corresponding to the ambient temperature T and the operating frequency f of the compressor. If so, and the first temperature difference ΔT1 exceeds the set temperature difference threshold, the operating frequency f of the compressor is reduced.

[0044] With a fixed compressor frequency f, the heat exchange capacity of the condenser in the heat pump unit 10 is also fixed. If the water flow rate into the heat pump unit 10 is large, the outlet water temperature T3 will be low. If the water flow rate into the heat pump unit 10 is small, the outlet water temperature T3 will be high. Therefore, the inlet and outlet water temperature difference of the heat pump unit 10 is negatively correlated with the water flow rate. The water flow rate can be judged based on the second temperature difference ΔT2 between the outlet water temperature T3 and the inlet water temperature T4 of the heat pump unit 10. The second temperature difference ΔT2 = outlet water temperature T3 - inlet water temperature T4. After prolonged use, scale will also form on the condenser of the heat pump unit 10, causing a decrease in the heat exchange efficiency of the condenser. The difference between the heat pump outlet water temperature T3 and the condenser condensing temperature T5 reflects the scale condition of the condenser. The thicker the scale in the condenser, the larger the third temperature difference ΔT3 between the heat pump outlet water temperature T3 and the condenser condensing temperature T5. The third temperature difference ΔT3 = heat pump outlet water temperature T3 - condenser condensing temperature T5.

[0045] Therefore, in a preferred embodiment, a third temperature sensor is further provided at the outlet of the heat pump host 10, and a fourth temperature sensor is provided at the inlet of the heat pump host 10 and / or a fifth temperature sensor is provided at the condenser of the heat pump host; thereby, the heat exchange status value of the heat pump host 10 obtained by the controller includes a second temperature difference ΔT2 between the outlet water temperature T3 measured by the third temperature sensor and the inlet water temperature T4 measured by the fourth temperature sensor, and / or, the heat exchange status value of the heat pump host 10 obtained by the controller includes a third temperature difference ΔT3 between the heat pump outlet water temperature T3 measured by the third temperature sensor and the condensation temperature T5 measured by the fifth temperature sensor.

[0046] In a preferred embodiment, the controller is further configured to shut down the heat pump host 10 when the outlet water temperature T3 reaches the set first temperature protection threshold Tx1 to prevent overheating and damage to the heat pump host 10; further, the controller is further configured to restart the heat pump host 10 after the heat pump host 10 is shut down due to overheating and the inlet water temperature T4 drops to less than or equal to the buffer water tank temperature T2, so that the heat pump host 10 can automatically start up and run when the temperature returns to the normal range.

[0047] In another optional embodiment, the controller is further configured to trigger high-temperature protection and shut down the heat pump host 10 when the outlet water temperature T3 reaches a set second temperature protection threshold Tx2, to prevent damage to the heat pump host 10 due to overheating. Furthermore, the controller is also configured to restart the heat pump host 10 after the overheating shutdown period has reached a set shutdown duration, and to operate the compressor of the heat pump host 10 at the lowest operating frequency. Operating the compressor at the lowest operating frequency is to avoid the heat pump host 10 continuing to heat beyond the original water temperature, thus preventing the heat pump host 10 from triggering high-temperature protection again. The second temperature protection threshold Tx2 is lower than the first temperature protection threshold Tx1 to prevent damage to the heat pump host 10 due to high temperature.

[0048] In a preferred embodiment, when the first temperature difference ΔT1 exceeds the set temperature difference threshold, the larger the first temperature difference ΔT1 is, the greater the reduction in the operating frequency f of the compressor of the heat pump host 10, so as to reduce the outlet water temperature T3 of the heat pump host 10 as quickly as possible, prevent the heat pump host 10 from overheating, and trigger the high temperature protection of the heat pump host 10.

[0049] In a preferred embodiment, the controller is further configured to:

[0050] When the preset first temperature threshold X1 < the first temperature difference ΔT1 < the preset second temperature threshold X2, the compressor frequency f is reduced by a preset first adjustment amount Δf1.

[0051] When the preset second temperature threshold X2 < the first temperature difference △T1 < the preset third temperature threshold X3, the compressor frequency f is reduced by a preset second adjustment amount △f2.

[0052] When the first temperature difference ΔT1 is greater than the preset third temperature threshold X3, the compressor frequency f is reduced by the preset third adjustment amount Δf3.

[0053] Wherein, the first temperature threshold X1 < the second temperature threshold X2 < the third temperature threshold X3, and the first adjustment amount △f1 < the second adjustment amount △f2 < the third adjustment amount △f3.

[0054] In an optional embodiment:

[0055] If the first temperature difference ΔT1 > 6℃, the compressor operating frequency f immediately drops by 10Hz, and after being forced to run for 60 seconds, the first temperature difference ΔT1 is re-detected.

[0056] If 1℃ < first temperature difference △T1 ≤ 6℃, the operating frequency will immediately drop by 5Hz, and after being forced to run for 60 seconds, the first temperature difference △T1 will be re-detected.

[0057] If 0℃≤first temperature difference △T1≤1℃, the operating frequency remains unchanged, and the compressor frequency adjustment range is limited to ±20% of the current frequency.

[0058] In other embodiments, the amount of reduction in compressor frequency f can also be determined directly based on the first temperature difference ΔT1, so as to achieve stepless adjustment of compressor frequency f.

[0059] If the first temperature difference ΔT1 is too large, a single adjustment of the compressor frequency f may not reduce the first temperature difference ΔT1 to below the set threshold. Therefore, the compressor frequency f needs to be adjusted multiple times. In a preferred embodiment, the controller is also used to obtain the buffer tank temperature T2 and the compressor operating frequency f again after the compressor frequency f is reduced. If the buffer tank temperature T2 is lower than the set target temperature T0 and the compressor frequency f is not reduced to the minimum operating frequency, the first temperature difference ΔT1 is obtained again. If the first temperature difference ΔT1 exceeds the set temperature difference threshold, the controller reduces the operating frequency f of the compressor of the heat pump host 10 again.

[0060] The compressor needs to operate at a certain frequency to ensure the amount of lubricating oil inside the compressor and keep the various parts inside the compressor lubricated. This frequency is the minimum oil return frequency of the compressor. If the compressor operates below the minimum oil return frequency for a long time, it will lead to excessive wear of the compressor and damage to the compressor.

[0061] In a preferred embodiment, the controller is further configured to adjust the compressor operating frequency f to operate at the minimum oil return frequency for a set first operating time after the compressor has operated at a state less than the minimum oil return frequency for a set second operating time. In a specific embodiment, after the compressor has operated at a state less than the minimum oil return frequency for 1 hour, the compressor operating frequency f is adjusted to operate at the minimum oil return frequency for 8 minutes.

[0062] On the other hand, the present invention also provides a control method for a heat pump water heater. The heat pump water heater controlled by this method includes a heat pump main unit 10, a buffer tank 20, and a coil 30 connected to the inlet and outlet ends of the heat pump main unit 10 and disposed within the buffer tank 20. Figure 2As shown, the method includes the following steps:

[0063] S102: Obtain the first temperature difference ΔT1 between the coil temperature T1 and the water tank temperature T2;

[0064] S103: If the first temperature difference △T1 exceeds the set temperature difference threshold, reduce the compressor's operating frequency f.

[0065] In a preferred embodiment, step S103 further includes the following steps:

[0066] S1031: When the preset first temperature threshold X1 < first temperature difference △T1 < preset second temperature threshold X2, the compressor frequency f is reduced by a preset first adjustment amount △f1;

[0067] S1032: When the preset second temperature threshold X2 < the first temperature difference △T1 < the preset third temperature threshold X3, the compressor frequency f is reduced by a preset second adjustment amount △f2.

[0068] S1033: When the first temperature difference △T1 is greater than the preset third temperature threshold X3, the compressor frequency f is reduced by the preset third adjustment amount △f3.

[0069] Wherein, the first temperature threshold X1 < the second temperature threshold X2 < the third temperature threshold X3, and the first adjustment amount △f1 < the second adjustment amount △f2 < the third adjustment amount △f3.

[0070] In a preferred embodiment, step S103 further includes the following steps:

[0071] S1034: After adjusting the compressor frequency f to be lower, repeat step S102.

[0072] In a preferred embodiment, the following step is included before step S102:

[0073] S101: Obtain the ambient temperature T, the compressor operating frequency f, and the heat exchange status value of the heat pump host, and determine whether the heat exchange status value is within the range of the heat exchange status threshold corresponding to the ambient temperature T and the operating frequency f. If so, proceed to step S102.

[0074] In a preferred embodiment, the heat exchange status value of the heat pump host obtained in step S101 includes a second temperature difference ΔT2 between the heat pump outlet water temperature T3 and the heat pump inlet water temperature T4, and / or a third temperature difference ΔT3 between the heat pump outlet water temperature T3 and the condenser condensing temperature T5.

[0075] In a preferred embodiment, the following steps are also included:

[0076] S104: Obtain the heat pump outlet water temperature T3;

[0077] S105: If the set first temperature protection threshold Tx1 is reached, the heat pump host 10 will be shut down;

[0078] S106: Obtain the heat pump inlet water temperature T4 and the buffer water tank temperature T2;

[0079] S107: If the heat pump inlet water temperature T4 is less than or equal to the buffer water tank temperature T2, restart the heat pump host 10; otherwise, repeat step S106.

[0080] In a preferred embodiment, the following steps are also included:

[0081] S108: Obtain the heat pump outlet water temperature T3;

[0082] S109: If the set second temperature protection threshold Tx2 is reached, the heat pump host 10 will be shut down;

[0083] S110: After the heat pump host 10 has been off for the set time, the heat pump host 10 is turned on again and the compressor of the heat pump host 10 is run at the lowest operating frequency.

[0084] In a preferred embodiment, the following steps are also included:

[0085] S111: After the compressor has been running at a frequency lower than the minimum oil return frequency for a set first operating time, the compressor operating frequency f is adjusted so that the compressor runs at the minimum oil return frequency for a set second operating time.

[0086] In a preferred embodiment, such as Figure 3 As shown, the control method of the heat pump water heater of the present invention includes the following steps:

[0087] S201: Obtain the ambient temperature T, the compressor operating frequency f, and the heat exchange status value of the heat pump host; wherein, the heat exchange status value of the heat pump host includes the second temperature difference △T2 between the heat pump outlet water temperature T3 and the heat pump inlet water temperature T4, and / or the third temperature difference △T3 between the heat pump outlet water temperature T3 and the condenser condensing temperature T5.

[0088] S202: If the heat exchange state value is within the range of the heat exchange state threshold corresponding to the ambient temperature T and the operating frequency f, then obtain the first temperature difference ΔT1 between the coil temperature T1 and the water tank temperature T2; wherein, the corresponding heat exchange state threshold is obtained by the ambient temperature T and the compressor operating frequency f.

[0089] S2031: When the preset first temperature threshold X1 < the first temperature difference △T1 < the preset second temperature threshold X2, the compressor frequency f is reduced by a preset first adjustment amount △f1;

[0090] S2032: When the preset second temperature threshold X2 < the first temperature difference △T1 < the preset third temperature threshold X3, the compressor frequency f is reduced by the preset second adjustment amount △f2.

[0091] S2033: When the first temperature difference △T1 > the preset third temperature threshold X3, the compressor frequency f is reduced by the preset third adjustment amount △f3.

[0092] S2034: Repeat step S102;

[0093] Wherein, the first temperature threshold X1 < the second temperature threshold X2 < the third temperature threshold X3, and the first adjustment amount △f1 < the second adjustment amount △f2 < the third adjustment amount △f3.

[0094] S204: Obtain the heat pump outlet water temperature T3;

[0095] S205: If the heat pump outlet water temperature T3 reaches the set first temperature protection threshold Tx1, then shut down the heat pump host 10.

[0096] S206: Obtain the heat pump inlet water temperature T4 and the buffer water tank temperature T2;

[0097] S207: If the heat pump inlet water temperature T4 is less than or equal to the buffer water tank temperature T2, then restart the heat pump host 10; otherwise, repeat step S206.

[0098] S211: If the compressor operates at a frequency lower than the minimum oil return frequency for a set first operating time, then adjust the compressor operating frequency f so that the compressor operates at the minimum oil return frequency for a set second operating time.

[0099] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0100] 1. By checking whether the temperature difference between the coil temperature and the buffer tank temperature exceeds the set temperature difference threshold, it can be determined whether the failure of the current tank water temperature to reach the target value is due to low heat exchange efficiency of the heating element caused by scale buildup. If so, the operating frequency of the compressor is reduced to lower the outlet water temperature of the heat pump unit and the water temperature returning to the heat pump unit from the coil, thereby preventing the heat pump unit from overheating.

[0101] 2. By measuring the temperature difference between the inlet and outlet water temperatures of the heat pump unit, as well as the temperature difference between the outlet water temperature and the condensing temperature of the heat pump unit, it can be determined whether the heat pump unit is in normal operating condition, thereby determining whether it is appropriate to adjust the compressor frequency.

[0102] 3. After the heat pump unit shuts down due to overheating, detect the heat pump inlet water temperature and the buffer water tank temperature. Restart the heat pump unit after the heat pump inlet water temperature drops to less than or equal to the buffer water tank temperature to achieve automatic restart after the heat pump unit shuts down due to overheating.

[0103] 4. After the compressor has been running at a frequency lower than the minimum oil return frequency for a set first operating time, adjust the compressor operating frequency f to make the compressor run at the minimum oil return frequency for a set second operating time to prevent excessive wear caused by the compressor running at a frequency lower than the oil return frequency for a long time.

[0104] The above-described embodiments are merely illustrative of several implementation methods of the embodiments of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the patent scope of the embodiments of this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the embodiments of this application, and these all fall within the protection scope of the embodiments of this application.

Claims

1. A heat pump water heater, characterized in that, include: The heat pump unit (10), the buffer water tank (20), and the coil (30) connected to the inlet and outlet of the heat pump unit (10) and installed in the buffer water tank, wherein the heat pump unit (10) includes a controller; The coil (30) is equipped with a first temperature sensor, and the buffer tank (20) is equipped with a second temperature sensor. The controller is connected to the first temperature sensor and the second temperature sensor respectively. The controller is used to obtain a first temperature difference ΔT1 between the coil temperature T1 measured by the first temperature sensor and the buffer tank temperature T2 measured by the second temperature sensor. It also includes an ambient temperature sensor, a third temperature sensor located at the outlet of the heat pump unit (10), a fourth temperature sensor located at the inlet of the heat pump unit (10), and a fifth temperature sensor located on the condenser of the heat pump unit. The controller is also used to acquire the ambient temperature T, the operating frequency f of the compressor and the heat exchange status value of the heat pump host (10), and to determine whether the heat exchange status value is within the range of the heat exchange status threshold corresponding to the ambient temperature T and the operating frequency f. If so, and the first temperature difference ΔT1 exceeds the set temperature difference threshold, the operating frequency f of the compressor is reduced. The heat exchange status value of the heat pump host (10) obtained by the controller includes the third temperature difference ΔT3 between the heat pump outlet water temperature T3 measured by the third temperature sensor and the condensation temperature T5 measured by the fifth temperature sensor.

2. The heat pump water heater according to claim 1, characterized in that: The heat exchange status value of the heat pump host (10) obtained by the controller also includes a second temperature difference △T2 between the heat pump outlet water temperature T3 measured by the third temperature sensor and the heat pump inlet water temperature T4 measured by the fourth temperature sensor.

3. The heat pump water heater according to claim 2, characterized in that: The controller is also used to shut down the heat pump host (10) when the heat pump outlet water temperature T3 reaches the set first temperature protection threshold Tx1, and to restart the heat pump host (10) after the heat pump inlet water temperature T4 drops to less than or equal to the buffer water tank temperature T2.

4. The heat pump water heater according to claim 3, characterized in that: The controller is also used to shut down the heat pump host (10) when the outlet water temperature T3 reaches the set second temperature protection threshold Tx2, and to restart the heat pump host (10) after the shutdown time of the heat pump host (10) reaches the set shutdown time, and to make the compressor of the heat pump host (10) run at the lowest operating frequency.

5. The heat pump water heater according to claim 1, characterized in that: When the first temperature difference △T1 exceeds the set temperature difference threshold, the larger the first temperature difference △T1 is, the greater the reduction in the operating frequency f of the compressor of the heat pump host (10).

6. The heat pump water heater according to claim 1 or 5, characterized in that, The controller is also used for: When the preset first temperature threshold X1 < the first temperature difference ΔT1 < the preset second temperature threshold X2, the compressor frequency f is reduced by a preset first adjustment amount Δf1. When the preset second temperature threshold X2 < the first temperature difference △T1 < the preset third temperature threshold X3, the compressor frequency f is reduced by a preset second adjustment amount △f2. When the first temperature difference ΔT1 is greater than the preset third temperature threshold X3, the compressor frequency f is reduced by the preset third adjustment amount Δf3. Wherein, the first temperature threshold X1 < the second temperature threshold X2 < the third temperature threshold X3, and the first adjustment amount △f1 < the second adjustment amount △f2 < the third adjustment amount △f3.

7. The heat pump water heater according to any one of claims 1-2, characterized in that: The controller is also used to obtain the buffer tank temperature T2 and the compressor operating frequency f again after the compressor frequency f is reduced. If the buffer tank temperature T2 is lower than the set target temperature T0 and the compressor frequency f is not reduced to the minimum operating frequency, the first temperature difference ΔT1 is obtained again. If the first temperature difference ΔT1 exceeds the set temperature difference threshold, the controller reduces the operating frequency f of the compressor of the heat pump host (10) again.

8. The heat pump water heater according to any one of claims 1-2, characterized in that: The controller is also used to adjust the compressor operating frequency f after the compressor has been running at a state less than the minimum oil return frequency for a set first operating time, so that the compressor runs at the minimum oil return frequency for a set second operating time.

9. A control method for a heat pump water heater, characterized in that, The heat pump water heater includes a heat pump main unit (10), a buffer water tank (20), and a coil (30) connected to the inlet and outlet of the heat pump main unit (10) and installed in the buffer water tank (20). The method includes the following steps: S101: Obtain the ambient temperature T, the compressor operating frequency f, and the heat exchange status value of the heat pump host, and determine whether the heat exchange status value is within the range of the heat exchange status threshold corresponding to the ambient temperature T and the operating frequency f. If so, proceed to step S102. The heat exchange status value of the heat pump host includes the third temperature difference ΔT3 between the heat pump outlet water temperature T3 and the condenser condensing temperature T5. S102: Obtain the first temperature difference ΔT1 between the coil temperature T1 and the water tank temperature T2; S103: If the first temperature difference △T1 exceeds the set temperature difference threshold, reduce the compressor's operating frequency f.

Images