Patent Grant
11067074
The present disclosure relates to compressor control and, more specifically, to a system and method for flooded start control of a compressor.
This section provides background information related to the present disclosure which is not necessarily prior art.
Compressors are used in a wide variety of industrial and residential applications to circulate refrigerant within refrigeration, HVAC, heat pump, or chiller systems (generally referred to as “refrigeration systems”) to provide a desired heating or cooling effect. In any of these applications, the compressor should provide consistent and efficient operation to ensure that the particular refrigeration system functions properly.
The compressor may include a crankcase to house moving parts of the compressor, such as a crankshaft. In the case of a scroll compressor, the crankshaft drives an orbiting scroll member of a scroll set, which also includes a stationary scroll member. The crankcase may include a lubricant sump, such as an oil reservoir. The lubricant sump can collect lubricant that lubricates the moving parts of the compressor.
When the compressor is off, liquid refrigerant in the refrigeration system generally migrates to the coldest component in the system. For example, in an HVAC system, during an overnight period of a diurnal cycle when the HVAC system is off, the compressor may become the coldest component in the system and liquid refrigerant from throughout the system may migrate to, and collect in, the compressor. In such case, the compressor may gradually fill with liquid refrigerant and become flooded.
One issue with liquid refrigerant flooding the compressor is that the compressor lubricant is generally soluble with the liquid refrigerant. As such, when the compressor is flooded with liquid refrigerant, the lubricant normally present in the lubricant sump can dissolve in the liquid refrigerant, resulting in a liquid mixture of refrigerant and lubricant.
Further, in an HVAC system, upon startup in the morning of a diurnal cycle, the compressor may begin operation in a flooded state. In such case, the compressor may quickly pump out all of the liquid refrigerant, along with all of the dissolved lubricant, in the compressor. For example, the compressor may pump all of the liquid refrigerant and dissolved lubricant out of the compressor in less than ten seconds. At this point, the compressor may continue to operate without lubrication, or with very little lubrication, until the refrigerant and lubricant returns to the suction inlet of the compressor after being pumped through the refrigeration system. For example, it may take up to one minute, depending on the size of the refrigeration system and the flow control device used in the refrigeration system, for the lubricant to return to the compressor. Operation of the compressor without lubrication, however, can damage the internal moving parts of the compressor, result in compressor malfunction, and reduce the reliability and useful life of the compressor. For example, operation of the compressor without lubrication can result in premature wear to the compressor bearings.
Traditionally, crankcase heaters have been used to heat the crankcase of the compressor to prevent or reduce liquid migration to the compressor and a flooded compressor state. Crankcase heaters, however, increase energy costs as electrical energy is consumed to heat the compressor. Additionally, while crankcase heaters can be effective for slow rates of liquid migration, crankcase heaters can be less effective for fast rates of liquid migration, depending on the size or heating capacity of the crankcase heater.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
An example embodiment of a system according to the present disclosure is provided and includes a compressor for a refrigeration system and a controller. The controller operates the compressor in a flooded-start control mode that includes operating the compressor according to at least one cycle having a first time period during which the compressor is on, followed by a second time period during which the compressor is off. The controller receives asset data corresponding to at least one of a type and a characteristic of at least one component of the refrigeration system. The controller determines at least one of the first time period, the second time period, and a number of cycles for the at least one cycle for the flooded-start control mode. The at least one of the first time period, the second time period, and the number of cycles is based on the received asset data. The controller operates the compressor in the flooded-start control mode after determining the first time period, the second time period, and the number of cycles.
In other features, the controller may communicate with other devices in the refrigeration system to receive the asset data.
In other features, the controller may receive the asset data from user input.
In other features, the asset data may indicate at least one of a specific type, a capacity, a model number, and a serial number for a flow control device of the refrigeration system.
In other features, the asset data may indicate at least one of a compressor type and a compressor capacity.
In other features, the type of the compressor may include data indicating whether the compressor is at least one of a multi-stage compressor, a variable capacity compressor, a modulated compressor, and a compressor having a delayed suction system.
In other features, the asset data may indicate whether the compressor is a direct suction compressor.
In other features, the asset data may indicate at least one of a type and a characteristic of a condenser of the refrigeration system.
In other features, the asset data may indicate at least one of a type and a characteristic of an evaporator of the refrigeration system.
In other features, the asset data may indicate whether the compressor includes a crankcase heater.
An example embodiment of a method according to the present disclosure is provided and includes operating, with a controller, a compressor of a refrigeration system. The controller is configured to operate the compressor in a flooded-start control mode that includes operating the compressor according to at least one cycle having a first time period during which the compressor is on, followed by a second time period during which the compressor is off. The method further includes receiving, with the controller, asset data corresponding to at least one of a type and a characteristic of at least one component of the refrigeration system. The method further includes determining, with the controller, at least one of the first time period, the second time period, and a number of cycles for the at least one cycle for the flooded-start control mode, where the at least one of the first time period, the second time period, and the number of cycles is based on the received asset data; and operating, with the controller, the compressor in the flooded-start control mode after determining the first time period, the second time period, and the number of cycles.
In other features, the method may further include communicating, with the controller, with other devices in the refrigeration system to receive the asset data.
In other features, the method may further include receiving, with the controller, the asset data from user input.
In other features, the asset data may indicate at least one of a specific type, a capacity, a model number, and a serial number for a flow control device of the refrigeration system.
In other features, the asset data may indicate at least one of a type and a capacity of the compressor of the refrigeration system.
In other features, the type of the compressor may include data indicating whether the compressor is at least one of a multi-stage compressor, a variable capacity compressor, a modulated compressor, and a compressor having a delayed suction system.
In other features, the asset data may indicate whether the compressor is a direct suction compressor.
In other features, the asset data may indicate a type and a characteristic of a condenser of the refrigeration system.
In other features, the asset data may indicate at least one of a type and a character of an evaporator of the refrigeration system.
In other features, the asset data may indicate whether the compressor includes a crankcase heater.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
In the drawings, reference numbers may be reused to identify similar and/or identical elements.
Example embodiments will now be described more fully with reference to the accompanying drawings.
The present disclosure relates to a system and method for starting a compressor while in a flooded state. More specifically, instead of quickly pumping out all of the liquid refrigerant and dissolved lubricant present in the compressor when in a flooded state, the flooded start control of the present disclosure provides for cycling the compressor with one or more short on/off cycles to gradually pump liquid from the compressor without completely emptying the compressor of liquid refrigerant and lubricant. In this way, more time is allowed for the refrigerant/lubricant to work through the refrigeration system and return to the compressor before the compressor is emptied of liquid. Further, the gradual pumping of liquid from the compressor allows more time for the compressor to heat up on its own due to operation of the electric motor in the compressor and due to the rotation of the internal moving parts of the compressor, such as the crank shaft and compression mechanism. Additionally, as the pressure within the suction chamber of the compressor decreases and the temperature within the suction chamber of the compressor increases due to operation of the compressor, the liquid refrigerant within the compressor can start to flash to gaseous refrigerant that is then pumped out of the system, leaving lubricant behind in the compressor.
In this way, utilizing a flooded start control with one or more on/off cycles to begin operation of the compressor in a flooded state can more efficiently and effectively handle and manage the liquid refrigerant and lubricant in the compressor, resulting in improved operation of the compressor. Additionally, utilizing a flooded start control with one or more on/off cycles to begin operation of the compressor in a flooded state can decrease the need for use of a crankcase heater, resulting in lower energy consumption costs. In some instances, a smaller more energy efficient crankcase heater can be used. In other instances, the need for a crankcase heater can be eliminated altogether.
As discussed in further detail below, the present disclosure includes systems and methods for detecting when to utilize a flooded start control. For example, the present disclosure includes determining an amount of liquid migration to the compressor and comparing the determined amount with a threshold to determine if the compressor is in a flooded state.
Additionally, the present disclosure includes systems and methods for implementing a flooded start control by utilizing one or more on/off cycles to begin operation of the compressor in a flooded state. For example, the compressor may be started with one or more cycles that include a two-second on-period followed by a five-second off-period per cycle. The present disclosure includes determining the on-period, the off-period, and the number of cycles to be utilized.
Additionally, the present disclosure includes systems and methods for optimizing the flooded start control based on the types of components and specific configuration and operating characteristics of the particular refrigeration system.
With reference to
A control module 20 controls the compressor 12 by turning the compressor 12 on and off. More specifically, the control module 20 controls a compressor contactor 40 (shown in
With reference again to
The control module 20 may also control a crankcase heater 26 attached to or located within the compressor 12. For example, the control module 20 may turn the crankcase heater 26 on and off, as appropriate, to provide heat to the compressor and, more specifically, to the crankcase of the compressor.
The control module 20 may be located at or near the compressor 12 at the condensing unit that houses the compressor 12 and condenser 14. In such case, the compressor 12 may be located outdoors. Alternatively, the compressor 12 may be located indoors and inside a building associated with the refrigeration system. Alternatively, the control module 20 may be located at another location near the refrigeration system 10. For example, the control module 20 may be located indoors. Alternatively, the functionality of the control module 20 may be implemented in a refrigeration system controller. Alternatively, the functionality of the control module 20 may be implemented in a thermostat located inside a building associated with the refrigeration system 10. Alternatively, the functionality of the control module 20 may be implemented at a remote computing device.
With reference to
With reference to
With reference to
With reference to
The control module 20 turns the electric motor 42 of the compressor on and off by opening and closing the compressor contactor 40 that connects or disconnects the common node (C) of the electric motor 42 to electrical terminal (L1).
With reference to
With reference to
With reference to
At 606, the control module 20 determines a compressor off-time corresponding to the length of time that the compressor has been off. In other words, the compressor off-time corresponds to the length of time since the compressor was last on. In terms of the compressor contactor 40, the compressor off-time corresponds to the length of time that the compressor contactor 40 has been open.
At 608, based on the temperature data and the compressor off-time, the control module 20 can estimate or determine the amount of liquid migration that has occurred. In other words, based on the temperature data and the compressor off-time, the control module 20 can estimate or determine the amount of liquid present within the compressor 12. In this way, the amount of liquid present in the compressor is calculated as a function of the temperature data and the compressor off-time.
As an example, Table 1 shows the functional relationship between outdoor ambient temperature, compressor off-time, and the amount of liquid present in an exemplary three-ton system capacity rated compressor. In Table 1, the compressor off-time is indicated in hours, the outdoor ambient temperature (OAT) is indicated in degrees Fahrenheit, and the amount of liquid refrigerant present in the compressor is indicated in pounds. In Table 1, and the similar tables that follow below, outdoor ambient temperatures of eighty and sixty degrees Fahrenheit are normally associated with operation of an HVAC system, or a reversible heat pump operating in a cooling mode, while outdoor ambient temperatures of forty and twenty degrees Fahrenheit are normally associated with operation of a heat pump operating in a heating mode.
The control module 20 may store a look-up table, similar to Table 1, in memory to determine the amount of liquid in the compressor 12 or the control module 20 may use a function to calculate the amount of liquid in the compressor 12. Also, although Table 1 shows liquid amounts based on outdoor ambient temperature, a similar table could be used based on compressor temperature, for example.
At 610, the control module 20 may compare the amount of liquid in the compressor 12 with a predetermined threshold. The predetermined threshold, for example, may be a percentage of a maximum liquid handling volume of the compressor 12. For example, the exemplary three-ton capacity compressor 12 may have a maximum liquid handling volume of six pounds of liquid refrigerant. The predetermined threshold for the three-ton capacity compressor 12 may be, for example, twenty percent of six pounds or 1.2 pounds.
When the amount of liquid in the compressor 12 is greater than the predetermined threshold, the control module 20 performs flooded start control at 612. As described in further detail below, the flooded start control utilizes one or more on/off cycles to begin operation of the compressor 12 in a flooded state. The number of cycles and the lengths of time for the on and off periods of the cycle may vary depending on the amount of liquid present in the compressor 12. For example, the two right-most columns of Table 2 show the number of cycles and the lengths of time for the on and off periods of each cycle in an example embodiment, utilizing the same liquid amounts from Table 1.
As shown, in Table 2, when the amount of liquid in the compressor 12 is 1.2 pounds or less, the flooded start control is not performed and there are no on/off cycles. When the amount of liquid in the compressor 12 is between 1.4 pounds and 2.7 pounds, one on/off cycle is performed whereby the compressor 12 is on for one second, then off for five seconds. When the liquid in the compressor 12 is between 2.8 pounds and 3.4 pounds, two on/off cycles are performed whereby for the first cycle the compressor 12 is on for one second and then off for five seconds and for the second cycle the compressor 12 is on for three seconds and then off for five seconds. When the liquid in the compressor 12 is between 3.5 pounds and 4.1 pounds, two on/off cycles are performed whereby for the first cycle the compressor 12 is on for one second and then off for five seconds and for the second cycle the compressor 12 is on for four seconds and then off for five seconds. Determination of the lengths of time of the on/off periods and of the number of cycles and performance of the flooded start control is described further below.
Once the control module 20 performs the flooded start control at 612, the control module 20 proceeds to 614 and performs normal compressor operation, i.e., compressor operation without flooded start control. Additionally, at 610 when the amount of liquid present in the compressor 12 is not greater than the predetermined threshold, the control module 20 proceeds to 614 and performs normal compressor operation. The control algorithm ends at 616.
With reference to
At 706, the control module 20 compares the compressor off-time with a predetermined time threshold. For example, the time threshold may be twelve hours. At 708, when the compressor off-time is greater than the predetermined time threshold, the control module 20 proceeds to 710 and performs flooded start control, which is also described above with respect to 612 of
With reference to
At 808, the control module 20 receives the compressor temperature. At 810, the control module 20 determines whether the outdoor ambient temperature is greater than the compressor temperature by a predetermined threshold amount. For example, the predetermined threshold amount may be fifteen degrees Fahrenheit and the control module 20 at 810 may determine whether the outdoor ambient temperature is greater than the compressor temperature by fifteen degrees Fahrenheit or more.
At 810, when the control module 20 determines that the outdoor ambient temperature is greater than the compressor temperature by fifteen degrees Fahrenheit or more, then a sudden liquid migration condition may be present and there may be a high amount of liquid migration into the compressor 12. For example, in an HVAC system, such a condition may occur in the morning after an overnight off period. Overnight, as the outside ambient temperature drops, the indoor temperature of a residence or commercial building associated with the HVAC system may remain higher than the outdoor ambient temperature. As such, liquid refrigerant from components of the HVAC system located within the building will migrate to the colder locations in the components of the HVAC system located outside the building, for example the compressor 12 and the outdoor condenser. Further, in the morning when the sun rises, the outdoor ambient temperature may begin to rise and may rise faster than a temperature of the compressor 12. For example, the compressor 12 may be located near the building in the shade and may not experience direct sunlight. As the outdoor ambient temperature rises quicker than the compressor temperature, additional liquid refrigerant may migrate, at a higher rate, into the compressor 12.
In the case of a sudden liquid migration, the amount of liquid in the compressor 12 may rise above the maximum liquid handling volume. As shown in Table 3, example amounts of liquid present in the compressor 12 are shown for a sudden liquid migration condition associated with different outside ambient temperatures.
At 810, when a sudden liquid migration condition is present, the control module 20 proceeds to 812 and performs flooded start control. Otherwise, the control module 20 proceeds to 814 and performs normal compressor operation, i.e., compressor operation without flooded start control.
At 812, the control module 20 performs flooded start control. As an example, the two right-most columns of Table 4 show the number of cycles and the lengths of time for the on and off periods in an example embodiment, utilizing the same liquid amounts from Table 3.
After performing flooded start control at 812, the control module 20 then proceeds to 814 and performs normal compressor operation, i.e., compressor operation without flooded start control.
With reference to
With reference to
At 1006, the control module 20 operates the compressor 12 based on the flooded start control parameters. At 1008, the control algorithm 1000 ends.
With reference to
Specifically, with reference to
With reference to
With reference to
The algorithms 1100, 1120, 1130 for calculating the flooded start control parameters may be done by the control module 20 during operation. Alternatively, the algorithms 1100, 1120, 1130 may be performed ahead of time for many different possible liquid amounts present in the compressor 12. The results of such calculations may be programmed into the control module 20 at installation. Additionally, the algorithms 1100, 1120, 1130 may be performed ahead of time for many different possible combinations of liquid amounts present in the compressor 12, compressor pumping capacities, and liquid migration capacity rates. As such, at installation or at the time of manufacture, the control module 20 may be programmed to access the applicable combination of parameters, or sub-group of parameters, based on the components present in the refrigeration system at installation.
Additionally, the flooded start control parameters may be adaptive such that the on-times and off-times may vary or progress from cycle to cycle. For example, a first cycle may include a one second on-time and a five second off-time. A second cycle may include a two second on-time and a five second off-time. A third cycle may include a three second on-time and a five second off-time. Additionally, the off-time may decrease as the cycles progress. For example, the first cycle may include a five second off-time, while the second cycle may include a four second off-time and the third cycle may include a three second off-time.
Additionally, the flooded start control parameters may be optimized to balance considerations of contactor life and compressor noise, on the one hand, and lubrication of the compressor 12 on the other. For example, additional cycling of the compressor 12 will negatively impact the life of the compressor contactor 40. Further, starting and stopping of the compressor 12 will result in audible changes in compressor operation. In other words, while the compressor 12 may not be very loud, the starting and stopping may be audible and noticeable to a nearby person, whereas continual operation may simply drone into background noise. Further, a nearby person may perceive there to be a problem when hearing the audible starting and stopping of the compressor 12. These considerations can be taken into consideration when determining the flooded start control parameters. With these considerations, it may generally be preferable to have no more than two to three cycles, with a ratio of approximately forty-percent of the cycle for on-time and sixty-percent of the cycle for off-time. As an example, two to three cycles, with an on-time of two seconds and an off-time of five seconds may be preferable.
Additionally, the flooded start control parameters may be adapted to whether the refrigeration system is a heat pump operating in a heating mode. For example, with a heat pump system operating in a heating mode, the number of cycles may be increased by thirty to forty percent or the on-time per cycle may be increased by about thirty to forty percent to accommodate the pumping capacity rate being lower due to the lower evaporator temperatures, as compared with an air conditioning cycle in an HVAC system or a heat pump system operating in a cooling mode.
With reference to
At 1208, the control module 20 may operate the compressor motor for one cycle based on the determined flooded start control on-time and off-time parameters. Additionally, the control module 20 may measure the electrical current of the compressor 12 during the on-time. At 1210, the control module 20 may compare the measured current from the last cycle with a predetermined current threshold. When the compressor 12 is pumping liquid, the associated electrical current spikes to a level that is higher than when the compressor 12 is only pumping gaseous refrigerant. For example, the electrical current level of a compressor 12 pumping liquid may be 2.5 times greater than the expected electrical current level for the same compressor 12 pumping gaseous refrigerant during normal operation under the same operating and ambient conditions (i.e., after the initial current in-rush in the initial 400 milliseconds time period). As such, the predetermined current threshold at 1210 may be, for example, 1.5 times the level of the normal expected electrical current for the compressor 12 when pumping gaseous refrigerant, under the same operating and ambient conditions.
At 1212, when the measured current is less than the predetermined current threshold, the control algorithm 1200 and cycling ends and no additional flooded start control is performed. At 1212, when the measured current is not less than the predetermined current threshold, the control algorithm 1200 loops back to 1204 and proceeds with another cycle.
With reference to
At 1306, the control module 20 may operate the compressor 12 for one cycle, based on the determined parameters. At 1308, the control module 20 may determine whether a locked rotor condition occurred during the last cycle. For example, during a three-second on-time, a locked-rotor condition may have occurred at the two-second mark due to the compressor 12 pumping liquid instead of gaseous refrigerant. At 1308, when a locked-rotor condition occurred, the control module 20 proceeds to 1310 and reduces the flooded start control on-time parameter. For example, the control module 20 may reduce the on-time parameter by one second at 1310. The control module 20 then proceeds to 1312 and checks to determine whether the adjusted on-time parameter is still greater than zero seconds. When the on-time parameter is still greater than zero seconds, the control module 20 loops back to 1306 and proceeds with the next cycle. At 1312, when the on-time parameter is at or below zero seconds, the control module 20 proceeds to 1314 to set the locked-rotor trip notification and then ends at 1318. At 1308, when a locked-rotor condition did not occur on the last cycle, the control module 20 proceeds to 1316 and operates the compressor 12 for any remaining flooded start control cycles and then ends at 1318. In this way, the control module 20 may adapt the on-time parameter on the fly to avoid a repeated locked rotor condition over successive cycles.
The control module 20 may also measure data associated with a flooded start, without using a flooded start control, to then determine flooded start parameters for use in the future when performing flooded start control. In this way, the control module 20 may initialize and learn characteristics of the refrigeration system 10, 30 that can then be used for flooded start control after initialization.
For example, the control module 20 may operate the compressor 12 in a flooded start condition, without using the flooded start control algorithms described herein, and may monitor discharge line temperature (DLT). As an example,
As shown, about four minutes and forty seconds of data is included in the graph. During that time, the outside ambient temperature graph line 1408 remained steady at about seventy five degrees Fahrenheit.
With respect to the compressor weight graph line 1402, at time zero, the compressor 12 includes about 8.5 pounds of liquid. Within the first ten seconds of normal operation, about 7.0 pounds of liquid has been pumped out of the compressor 12. At about 45 seconds, the entire 8.5 pounds of liquid has been pumped out of the compressor 12 and the compressor 12 is now operating without lubrication and without any liquid inside the compressor 12. At about 45 seconds, the compressor weight graph line 1402 is at its lowest point. At this point, refrigerant and lubricant begin to return to the compressor 12 and the compressor weight begins to increase. After fluctuations over the next 2 to 2.5 minutes, the compressor weight normalizes around the 3:00 minute mark, with about two pounds of liquid in the compressor 12, such liquid being mostly compressor lubricant.
With respect to the suction pressure graph line 1404, the suction pressure is pumped down about 66 psi in the first ten seconds and then drops further in the next ten seconds. The suction pressure then increases somewhat, as refrigerant and lubricant begin to return to the suction side of the compressor 12. After about the forty second mark, the suction pressure begins to normalize.
With respect to the discharge line temperature graph line 1406, like the compressor weight graph line 1402, the discharge line temperature graph line 1406 fluctuates over the first three minutes of operation before normalizing. Further, the discharge line temperature decreases roughly when the compressor weight increases. In other words, the discharge line temperature can be used to estimate the amount of time it takes for the compressor 12 to pump all liquid out of the compressor 12, the amount of time it takes for liquid to begin to return to the compressor 12, and the amount of time it takes for the compressor to normalize to a steady state. The control module 20 can use this data as historical data to learn appropriate flooded start control parameters for future use. For example, based on monitoring the discharge line temperature data, the control module 20 may be able to determine the amount of time it takes for the compressor 12 to completely pump out the liquid contents of the compressor 12 (i.e., about forty-five seconds) and the amount of time it takes for the compressor 12 to normalize operation after a flooded start (i.e., about three minutes). The control module 20 can use this data, for example, to determine that two to three cycles may be required and that the total on-time for all cycles may be less than ten seconds for future flooded start control.
With respect to
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With reference to
At 1708, based on the monitored system operating conditions during the normal flooded start, the control module 20 determines the flooded start parameters including, for example, the on-time, off-time, and number of cycles parameters. For example, based on the monitored discharge line temperature of the compressor 12, as discussed above with respect to
In addition to the various data described above used to calculate flooded start control parameters, other sensors and data can be used in addition to, or in place of, the above described sensors and data. For example, the optimum flooded start control parameters may be determined based on suction pressure sensed by a suction pressure sensor, suction temperature sensed by a suction temperature sensor, discharge line pressure sensed by a discharge line pressure sensor, discharge line temperature sensed by a discharge line temperature sensor, mass flow sensed by a mass flow sensor, oil level sensed by an oil level sensor, liquid level sensed by a liquid level sensor, bottom shell temperature sensed by a bottom shell temperature sensor, motor temperature sensed by a motor temperature sensor, and any other temperature, pressure, or other data or parameters related to the amount of liquid present in the compressor 12.
As discussed above, the flooded start control may be used in conjunction with a crankcase heater 26. For example, a crankcase heater 26 may be suitable for slow liquid migration conditions, while the flooded start control described herein may be reserved for fast liquid migration conditions.
With reference to
At 1806, when the liquid migration rate is not greater than the first liquid migration rate threshold, the control module 20 compares the liquid migration rate with a second liquid migration rate threshold at 1810. The second liquid migration rate threshold is less than the first liquid migration rate threshold. When the liquid migration rate is greater than the second liquid migration rate threshold, but less than the first liquid migration rate threshold, a slow liquid migration condition is present and the control module 20 proceeds to 1812 to activate the crankcase heater and then to 1814 to end.
With reference to
In this way, when the compressor 12 is completely filled with liquid, both the flooded start control and the crankcase heater are used together. Additionally, the control module 20 may determine that the compressor 12 is completely filled with liquid based on a current spike, i.e., a substantial increase in the amount of current flowing to the compressor 12. For example, the current spike may be 2.5 times the normal expected amount of current flowing to the compressor 12 in normal operation under the same operating and ambient conditions (i.e., after the initial current in-rush in the initial 400 milliseconds time period). Additionally, the control module 20 may determine that the compressor 12 is completely filled with liquid based on a locked rotor condition. In each of these additional cases, the control module 20 may then use the flooded start control together with activating of the crankcase heater.
With reference to
The received asset data may include information related to various system component types and capacities. For example, the asset data may indicate the type of flow control device present in the refrigeration system 10, 30, the type of condenser or evaporator present in the refrigeration system 10, 30, whether the compressor 12 is a variable capacity compressor or a multi-stage compressor, or whether multiple compressors are present in the refrigeration system 10, 30. Additionally, for example, the asset data may indicate the type of compressor such as a high-side scroll compressor (i.e., motor is located in a discharge pressure zone of the compressor 12), a low-side scroll compressor (i.e., motor is located in a suction pressure zone of the compressor 12), a directed suction low-side scroll compressor (i.e., suction inlet 52 is connected, directly or loosely, to the scroll set 50 inlet of the compressor 12), a high-side rotary compressor, or a low-side rotary compressor.
In the case of a multi-stage compressor, since the flooded start control depends on the pumping rate of the system, it is preferable to apply the flooded start control in a lower capacity stage. In the case of multiple compressors, it is preferable to apply the flooded start control to one of the multiple compressors.
At 2006, the control module 20 determines compressor pumping capacity and system liquid migration capacity rates based on the received asset data. At 2008, the control module 20 determines the flooded start control parameters, including on-time, off-time, and number of cycles, based on the determined pumping capacity and determined liquid migration capacity rate. At 2010, the control module 20 stores the flooded start operating parameters for use with flooded start control in the future. At 2012, the control module 20 ends.
Additionally, the asset data discussed above may indicate that the compressor 12 is a directed suction type compressor. In such case, the flooded start control parameters may be adjusted to account for the different pumping rates associated with a direct suction type compressor. Specifically, with a directed suction type compressor, the pumping rate is significantly lower by a factor proportional to the ratio of the scroll volume to the compressor shell volume. As such, with a direct suction type compressor, the flooded start control on-time parameter may need to increase by a factor of five to ten times, as compared with a non-direct suction type compressor. Alternatively, the control module 20 may be configured not to perform flooded start control when a direct suction type compressor is discovered as part of the asset data.
During operation of a standard low-side compressor 12, the liquid inside the compressor 12 is taken from the interior of the compressor 12, through the suction intake of the scroll set 50, through the discharge of the scroll set 50, and out through a discharge outlet 90 of the compressor 12. In contrast, for a directed suction type compressor 12 the suction inlet 52 is connected directly or loosely to the suction intake 85 of the scroll set 50. In such case, liquid enters the compressor 12 through the suction inlet 52 and then enters the scroll set 50. The liquid then seeps into the interior of the compressor 12 through the scroll set 50. During operation of the directed suction type compressor 12, liquid is taken both from the suction inlet 52 and the interior of the compressor 12. For a directed suction type compressor, however, the pressure within the suction inlet 52 will decrease faster than the pressure within the remainder of the interior of the suction chamber of the compressor 12. Further, liquid from inside the compressor 12 will seep back into the scroll set 50 for pumping out of the compressor 12 through the discharge outlet 90.
When utilizing the flooded start control of the present disclosure with a directed suction type compressor 12, these different pumping rates, resulting from the configuration of the direction suction type compressor, can be taken into account.
The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in another embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. Therefore, while this disclosure includes particular examples, the scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the claims.
As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.
In this application, including the definitions below, the term module may be replaced with the term circuit. The term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.
The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared processor encompasses a single processor that executes some or all code from multiple modules. The term group processor encompasses a processor that, in combination with additional processors, executes some or all code from one or more modules. The term shared memory encompasses a single memory that stores some or all code from multiple modules. The term group memory encompasses a memory that, in combination with additional memories, stores some or all code from one or more modules. The term memory may be a subset of the term computer-readable medium. The term computer-readable medium does not encompass transitory electrical and electromagnetic signals propagating through a medium, and may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory tangible computer readable medium include nonvolatile memory, volatile memory, magnetic storage, and optical storage.
The apparatuses and methods described in this application may be partially or fully implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on at least one non-transitory tangible computer readable medium. The computer programs may also include and/or rely on stored data.
This application is a divisional of U.S. patent application Ser. No. 14/947,146, filed on Nov. 20, 2015, which is a continuation of U.S. patent application Ser. No. 14/250,704, filed on Apr. 11, 2014 and issued as U.S. Pat. No. 9,194,393, which claims the benefit of U.S. Provisional Application No. 61/811,440, filed on Apr. 12, 2013. The entire disclosures of the above applications are incorporated herein by reference.
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| Number | Date | Country | |
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| Number | Date | Country | |
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| Number | Date | Country | |
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| Parent | 14947146 | Nov 2015 | US |
| Child | 16670709 | US |
| Number | Date | Country | |
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| Parent | 14250704 | Apr 2014 | US |
| Child | 14947146 | US |
