JP5113447B2 - Control method for heat pump water heater - Google Patents

Description

  The present invention relates to a control method of a heat pump hot water supply apparatus, and more particularly to a control method of a heat pump hot water supply apparatus that regulates a set upper limit temperature of hot water generated by a water heat exchanger.

  In general, the heat pump hot water supply apparatus controls the hot water to reach a set temperature.

  However, the conventional heat pump hot-water supply device has been controlled so that the hot water temperature becomes the set temperature regardless of the outside air temperature that changes according to the season.

  For this reason, since the tapping temperature is constant at the low outside air temperature, the condensation pressure does not change, the evaporation pressure decreases, the pressure difference between the compressor discharge and the suction increases, and an excessive burden is placed on the compressor. In addition, by controlling the current that flows to the inverter that controls the operating frequency of the compressor at high outside air temperature, or by repeatedly stopping operation and returning to operation with high pressure protection that prevents the condensation temperature of the water heat exchanger from rising, There was a problem that the compressor became short intermittent operation and became unpreferable in terms of the reliability of the compressor.

  Further, the conventional heat pump hot water supply apparatus only abnormally stops the heat pump hot water supply apparatus when the water temperature is lowered to prevent water freezing at the time of defrosting.

In Patent Document 1, when the outside air temperature is high, the discharge pressure of the compressor does not exceed the preset maximum normal discharge pressure, and when the outside air temperature is low, the discharge temperature of the compressor is There has been proposed a control method for a heat pump hot-water supply device for controlling the opening degree of the pressure reducing device so as not to exceed a preset normal maximum discharge temperature.
JP 2000-346447 A

  The present invention has been made in consideration of the above-described circumstances, and can regulate the upper limit of the pressure difference between the discharge pressure and the suction pressure of the compressor, and can improve the reliability of the compressor. It is an object to provide a control method.

In order to achieve the above-described object, a method for controlling a heat pump hot water supply apparatus according to the present invention includes a water heat exchanger that heats water to generate hot water and a refrigeration cycle that incorporates a compressor that compresses refrigerant. In the apparatus control method, the number of rotations of the compressor is controlled so that the water outlet temperature of the water heat exchanger becomes a set temperature, and when the outside air temperature is equal to or lower than a predetermined temperature, the water heat exchanger generates the water heat exchanger. It is characterized by regulating and changing the set upper limit temperature of hot water.

  According to the control method of the heat pump hot water supply apparatus according to the present invention, the upper limit of the pressure difference between the discharge pressure and the suction pressure of the compressor can be regulated, and the reliability of the compressor can be improved. A control method can be provided.

  The control method of the heat pump hot-water supply apparatus which concerns on one Embodiment of this invention is demonstrated with reference to drawings.

  FIG. 1 is a conceptual diagram of a heat pump hot water supply apparatus that implements a control method for a heat pump hot water supply apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, a heat pump water heater 1 according to this embodiment includes a compressor 2, a four-way valve 3, a water heat exchanger 4, a first expansion valve 5 that opens and closes a refrigerant flow path, and expands the refrigerant to low temperature and low pressure. The second expansion valve 6 and the outdoor heat exchanger 7 to be made are sequentially connected by piping, and further, a defrosting bypass circuit 10 including a check valve 8 and a two-way valve 9 is provided in parallel with the water heat exchanger 4, A refrigeration cycle S1 having one end connected between the first expansion valve 5 and the second expansion valve 6 is provided. The first expansion valve 5 can be replaced with a two-way valve.

  The water heat exchanger 4 is connected to the water supply side of the hot water storage tank 13 via the water supply pump 11 and the pipe joints 12 and 12 to form a hot water supply circuit S2. The hot water storage tank 13 includes a hot water supply pipe 14 and water supply. A pipe 15 is connected.

As shown in FIG.1 and FIG.2, the heat pump type hot water supply apparatus 1 includes a control device 16 that controls the entire device, and the control device 16 includes an inverter circuit 2a via a necessary interface (not shown). Included inverter-type variable-speed compressor 2, outdoor heat exchanger blower 17, four-way valve 3, water supply pump 11, suction refrigerant temperature sensor s ₁ provided in the suction side piping of the compressor 2, and provided in the discharge side piping The discharged refrigerant temperature sensor s ₂ , the water heat exchanger temperature sensor s ₃ provided in the water heat exchanger ₄ , the outdoor heat exchanger temperature sensor s ₄ provided in the refrigerant inlet side pipe of the outdoor heat exchanger 7, and the outdoor heat exchange The outside air temperature sensor s ₅ provided in the vicinity of the air suction side of the vessel 7, the water inlet temperature sensor s ₆ provided in the water supply side piping of the water heat exchanger 4, and the water outlet temperature sensor s ₇ provided in the hot water side piping are connected. The

The control device 16 includes a CPU 16a and a memory 16b. Based on the temperature information from each of the temperatures s _{1 to} s ₇ or the contents of the operation command information instructed by the user, the compressor 3 via the inverter circuit 2a, the first The expansion valve 5, the second expansion valve 6, the outdoor heat exchanger blower 17, the operation of the feed water pump 11, the operation of the four-way valve 3, etc. are controlled.

  Next, the control method (at the time of hot water supply operation) of the heat pump hot water supply apparatus of this embodiment is demonstrated.

  In the refrigeration cycle S1 of the heat pump water heater 1 shown in FIG. 2, the high-temperature and high-pressure gas refrigerant discharged from the compressor 2 flows to the water heat exchanger 4 through the four-way valve 3 and dissipates heat to the hot water supply circuit S2. The heat condensed and radiated from the refrigerant is supplied to the water in the hot water supply circuit S2 to generate hot water.

  The water heat exchanger 4 is supplied with water at a constant flow rate using a water supply pump 11, the water (hot water) outlet temperature is detected by the water outlet temperature sensor s7, and the water outlet temperature (hot water temperature) becomes the set temperature. Further, the rotational speed of the compressor 2 is controlled via the control device 16 and the inverter circuit 2a.

  The temperature difference between the water inlet temperature and the water outlet temperature is determined as the upper limit of the heating temperature based on the flow rate of water and the heating capacity of the water heat exchanger 4.

  Usually, when the water inlet temperature, that is, the condensation temperature is constant, the pressure on the high pressure side of the compressor 2 is substantially constant regardless of the outside air temperature. Since the temperature of the hot water is constant, the pressure on the low pressure side decreases according to the outside air at a low outside air temperature, and the high / low pressure difference (ΔP) between the suction side and the discharge side of the compressor 2 increases. When this ΔP becomes large, the load applied to the compressor 2 becomes large, and the operation in a state where the compressor 2 is not reliable is continued.

  In the past, the lower limit of the outside air temperature range was determined, and operation was not performed below the lower limit. However, in actual operation, when the engine was operated below the lower temperature limit, the compressor 2 continued to operate with a heavy load. Will do.

The outside air temperature measured by the outside air temperature sensor s _5, when the temperature of the outside air temperature sensor s ₅ becomes a predetermined prescribed temperature or less, the △ P at low outside air temperature by regulating (reducing) the set temperature upper limit The upper limit of the load applied to the compressor 2 is restricted.

  FIG. 3 shows the correlation between the outside air temperature, the water inlet temperature, and the usage range of the compressor 2.

  When the outside air temperature is 7 ° C., the compressor 2 is within the proper use range in any case where the water inlet temperature is 60 ° C., 55 ° C., or 50 ° C. When the outside air temperature is −7 ° C., the water inlet temperature is 55 When the temperature is 50 ° C. or 50 ° C., the compressor 2 is within the proper use range, but when the water inlet temperature is 60 ° C., the compressor 2 is out of the proper use range.

  FIG. 4 shows an example of the upper limit regulation value (temperature) of the outside air temperature and the set temperature.

  When the outside air temperature is in the range of −5 ° C. to 25 ° C., the upper limit value of the water outlet temperature (hot water temperature) is 65 ° C., and outside the range of −5 ° C. to 25 ° C., the upper limit of the water outlet temperature is set. The value is 58 ° C.

  As described above, when the outside air temperature becomes a predetermined temperature, for example, −5 ° C. or lower, the upper limit of the set temperature is lowered from 60 ° C. to 58 ° C. to suppress ΔP and the load applied to the compressor 2 Regulate the upper limit of.

  If the water inlet temperature decreases, the water outlet temperature also decreases, and the pressure on the high pressure side of the compressor 2 also decreases. Therefore, if the temperature difference at the water inlet / outlet is not regulated but the set temperature upper limit is determined, Δ P can be regulated.

  Thereby, even at the time of low outside air temperature, the upper limit of the high / low pressure difference (ΔP) of the compressor 2 can be regulated, and the reliability of the compressor 2 is improved.

  During the hot water supply operation, it is necessary to regulate the current flowing through the inverter 2a and protect the compressor 2.

  Conventionally, when the current exceeds the upper limit value under high outside air temperature conditions, the upper limit of the operating frequency (Hz) of the compressor 2 is restricted, and the compressor 2 becomes lower than the minimum frequency and the compressor 2 stops. When the compressor 2 is stopped, the compressor 2 is restarted after a predetermined time has elapsed since the stop, and when the current exceeds the upper limit value again, the compressor 2 is stopped. The reliability of the machine 2 was not good.

  In contrast, in the present embodiment, it is determined that the operation of the compressor 2 cannot be continued when the current exceeds the upper limit value and the compressor 2 is stopped once or n times. Stop. In addition, the re-operation start condition after the operation stop of the compressor 2 is lower than the outside air temperature at which the compressor 2 is stopped, for example, 5K lower. Thereby, frequent stoppage of the compressor 2 is prevented.

  The count of n times that the compressor 2 is stopped is cleared if the operation continues for a certain period after the operation of the compressor is resumed. By this control, frequent operation on / off of the compressor 2 due to the current protection of the inverter 2a can be prevented, and the reliability of the refrigeration cycle is improved.

Specific control contents are described below.
Judgment condition: (outside temperature ≧ β (for example, 43 ° C.) + Stop of compressor 2 due to current protection) ≧ 1 or n times The count clear condition of n times is a constant time (for example, 10 minutes), and the compressor 2 continues to operate. Operation at the time of determination: Operation stop of the compressor 2 Operation stop release condition of the compressor 2: Outside air temperature ≦ Outside air temperature at the determination condition−α (for example, 5K)

  Further, during the hot water supply operation, when the flow rate of water to the water heat exchanger 4 is extremely small, the condensation temperature rises and the compressor 2 is repeatedly turned on / off due to high pressure protection. In order to prevent such a state, when the compressor is stopped m times by high pressure protection when the pressure is increased, it is determined that the operation of the compressor 2 cannot be continued and the operation of the compressor 2 is stopped. The count m, which is the number of stops of the compressor 2, is cleared if the operation continues for a certain time after the operation of the compressor 2 is restored.

  By performing such control, it is possible to prevent frequent on / off operation of the compressor 2 due to high pressure protection due to an increase in the condensation temperature, and the reliability of the refrigeration cycle is improved. In particular, it is possible to prevent short intermittent operation due to high-pressure protection when there is an abnormality such as a decrease in flow rate.

Specific control contents are described below.
Judgment condition: number of stops of compressor 2 due to high pressure protection due to increase in condensation temperature ≧ m (for example, 40 times)
The count clear condition of m times is a fixed time (for example, 10 minutes).

  Further, when the outside air temperature becomes a predetermined temperature, for example, 25 ° C. or more, if the set temperature upper limit is lowered from 60 ° C., for example, to 58 ° C., the current protection of the inverter 2a and the high pressure protection by increasing the condensation temperature are achieved. The stop of the compressor 2 can be prevented. In particular, short intermittent operation of the compressor 2 is avoided, and the reliability of the compressor 2 is improved.

  Moreover, the control method (at the time of a defrost operation) of the heat pump hot-water supply apparatus of this embodiment is demonstrated.

  In the defrosting control of the heat pump water heater (refrigeration cycle), the normal defrosting defrosts the outdoor heat exchanger 7 to which the refrigerant discharged from the compressor 2 has frosted, and the first expansion valve 5, The water flows into the water heat exchanger 4 through the second expansion valve 6. Defrosting is performed by receiving heat from the hot water in the water heat exchanger 4 and returning to the compressor 2 through the four-way valve 3 again.

  However, when the temperature of the hot water flowing into the water heat exchanger 4 is lowered, the water heat exchanger 4 may be frozen. Conventionally, the water inlet temperature TWi or the water outlet temperature TWo is a constant temperature. When it became below, defrosting was stopped and the abnormality was displayed. In this case, although freezing can be prevented, the refrigeration cycle does not complete defrosting, but abnormally stops in a frosted state.

  On the other hand, the control method at the time of defrosting operation of the heat pump hot-water supply apparatus of this embodiment WHEREIN: The water inlet temperature TWi, the water outlet temperature TWo, the water heat exchanger temperature Tc falls, and there exists a possibility that the water heat exchanger 4 may freeze. For example, “TWi ≧ γ (for example, 2 ° C.), TWo ≧ γ (for example, 2 ° C.), Tc ≧ ε (for example, −10 ° C.) continues for p seconds (for example, 25 seconds)”, and the bypass circuit 10 is opened. By closing the first expansion valve 5, the refrigerant at the time of defrosting is not allowed to flow into the water heat exchanger 4 and is bypassed to prevent freezing. In this case, defrosting is performed without using hot water.

  Even if the first expansion valve 5 is not closed and the refrigerant flows through the bypass circuit 10 in parallel with the water heat exchanger 4, the amount of refrigerant flowing into the water heat exchanger 4 can be reduced, and the water heat exchanger 4 can be prevented from freezing. .

A specific control method is described below.
Freezing judgment condition: TWi <2 ° C. or TWo <2 ° C. is continued for 25 seconds, or Tc <−10 ° C. is continued for 25 seconds. Operation during freezing judgment: As shown in FIG. 5, the first expansion valve 5 is closed, The two-way valve 9 is opened and the water 4 is completely bypassed.

  Or as shown in FIG. 6, the two-way valve 9 is open | released and the water heat exchanger 4 and the bypass circuit 10 are flowed in parallel. The bypass state is continued until the defrosting is completed.

  Water temperature decreases during defrosting operation (when water inlet temperature and water outlet temperature are below a certain temperature for a certain period of time) or water heat exchanger temperature decreases (when a certain temperature is below a certain temperature for a certain period of time) By determining that the exchanger may freeze and opening the bypass circuit 10, the refrigerant is not allowed to flow through the water heat exchanger 4, or the refrigerant is allowed to flow through the water heat exchanger 4 and the bypass circuit 10 in parallel. By reducing the amount of refrigerant to the heat exchanger 4, freezing of the water heat exchanger 4 can be prevented.

  According to the control method of the heat pump hot water supply apparatus of this embodiment, the upper limit of the pressure difference between the discharge pressure and the suction pressure of the compressor 2 can be regulated, and the reliability of the compressor 2 can be improved. A device control method is realized.

The conceptual diagram of the heat pump hot-water supply apparatus which implements the control method of the heat pump hot-water supply apparatus of one Embodiment of this invention. The control circuit diagram of the heat pump hot-water supply apparatus which implements the control method of the heat pump hot-water supply apparatus of one Embodiment of this invention. FIG. 3 in the control method of the heat pump hot water supply apparatus of one embodiment of the present invention is a diagram showing the correlation between the outside air temperature, the water inlet temperature, and the compressor use range. The figure which shows the correlation of the upper limit regulation value of outside temperature and preset temperature in the control method of the heat pump hot-water supply apparatus of one Embodiment of this invention. The refrigeration cycle figure at the time of the hydrothermal exchanger freezing determination in the control method of the heat pump hot-water supply apparatus of one Embodiment of this invention (bypass defrost). The refrigerating cycle figure at the time of the hydrothermal exchanger freezing determination in the control method of the heat pump hot-water supply apparatus of one Embodiment of this invention (parallel defrost).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heat pump hot-water supply apparatus, 2 ... Compressor, 2a ... Inverter circuit, 3 ... Four-way valve, 4 ... Water heat exchanger, 5 ... 1st expansion valve, 6 ... 2nd expansion valve, 7 ... Outdoor heat exchanger , 8 ... Check valve, 9 ... Two-way valve, 10 ... Bypass circuit, 11 ... Water supply pump, 12 ... Pipe joint, 13 ... Hot water storage tank, 14 ... Hot water supply pipe, 15 ... Water supply pipe, 16 ... Control device, 16a ... CPU, 16b ... memory, 17 ... outdoor heat exchanger fan, S1 ... refrigeration cycle, S2 ... hot water circuit, s 1 _... suction refrigerant temperature sensor, s 2 _... discharged refrigerant temperature sensor, it s 3 _... water heat exchange sensor, s ₄ ... outdoor heat exchange temperature sensor, s ₅ ... outside temperature sensor, s ₆ ... water inlet temperature sensor, s ₇ ... water outlet temperature sensor.

Claims (5)

In a control method for a water heat exchanger that heats water to generate hot water and a heat pump hot water supply apparatus that includes a refrigeration cycle that incorporates a compressor that compresses refrigerant , the water outlet temperature of the water heat exchanger becomes a set temperature. The control of the heat pump hot water supply device, which controls the rotational speed of the compressor and regulates and changes the set upper limit temperature of hot water generated by the water heat exchanger when the outside air temperature is equal to or lower than a predetermined temperature. Method. By regulating the current flowing through the inverter that controls the operating frequency of the compressor incorporated in the refrigeration cycle, when the condition that the operating frequency of the compressor is lower than a predetermined value occurs a predetermined number of times, The method of controlling a heat pump water heater according to claim 1, wherein the operation is stopped and the operation restart after the operation is stopped is performed when the temperature is lower than the outside air temperature at the time of the operation stop. In order to prevent an increase in the condensation temperature of the water heat exchanger, the operation of the compressor is stopped when a condition that the operation frequency of the compressor is lower than a predetermined value occurs a predetermined number of times. The control method of the heat pump hot-water supply apparatus of Claim 1 . The method for controlling a heat pump hot water supply apparatus according to claim 3, wherein when the outside air temperature is equal to or higher than a predetermined temperature, a set upper limit temperature of hot water generated by the water heat exchanger is regulated. During the defrosting operation of the refrigeration cycle, when the water inlet temperature and the water outlet temperature of the water heat exchanger are below a predetermined temperature for a certain time, or the temperature of the water heat exchanger is below a predetermined temperature for a certain time In addition, it is determined that the water heat exchanger is frozen, and a part or all of the refrigerant flowing through the water heat exchanger is caused to flow through a bypass circuit to control the refrigerant flowing through the water heat exchanger. Item 2. A method for controlling a heat pump water heater according to Item 1.

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