Patent ID: 12202316

DETAILED DESCRIPTION

Embodiments of the present disclosure and its advantages are best understood by referring toFIGS.1through7of the drawings, like numerals being used for like and corresponding parts of the various drawings.

The extent of cooling and dehumidification an HVAC system can achieve is generally determined by its sensible capacity (Sc) and latent capacity (Lc). Each HVAC system has a total capacity (Tc), which is the sum of the sensible capacity and latent capacity (i.e., Tc=Sc+Lc). Generally, sensible capacity refers to an ability of the HVAC system to remove sensible heat from conditioned air (i.e., to cool the air). As used herein, sensible heat refers to heat that, when added to or removed from the air, results in a temperature change of the conditioned air. Comparatively, latent heat refers to the ability of an HVAC system to remove latent heat from conditioned air (i.e., to dehumidify the air). As used herein, latent heat refers to heat that, when added to or removed from the conditioned air, results in a phase change of, for example, water within the conditioned air. Sensible capacity and latent capacity may vary with environmental conditions.

HVAC systems are generally operated to achieve a sensible heat ratio (“S/T ratio”), where S/T ratio=Sc/Tc, of about 0.75. For the example of a 0.75 S/T ratio, an HVAC system is devoting 75% of its total capacity to removing sensible heat (i.e., for cooling) and 25% of its total capacity to remove latent heat (i.e., for dehumidification). Generally, an increased S/T ratio relative to this value is associated with an increase in the humidity of the conditioned air, while a decreased S/T ratio is associated with dehumidification of the conditioned air.

The S/T ratio generally changes proportionally with the ratio of the flow rate of air provided by the blower to the tonnage of the HVAC system (i.e., the “CFM/ton” of the HVAC system). The flow rate of air provided by the blower is generally measured in units of cubic feet per minute (CFM). The tonnage of the HVAC system corresponds to the cooling capacity of the system, where one “ton” of cooling corresponds to 12000 Btu/hr. The tonnage of the HVAC system is largely determined by the speed of the compressor(s) of the system, such that a decreased compressor speed corresponds to a decreased tonnage. The relationship between compressor speed and system tonnage is approximately linear. Accordingly, the CFM/ton value of an HVAC system, and thus the associated S/T Ratio, may be controlled by adjusting the flow rate of air provided by the blower and/or the tonnage of the HVAC system. For example, at a constant air flow rate from the blower, the speed of a variable-speed compressor may be decreased, to increase the CFM/ton value and the associated S/T Ratio of the system.

As described above, prior to the present disclosure, there was a lack of tools for improving comfort in a conditioned space in response to a demand request. This disclosure encompasses the unique recognition that the S/T ratio or the CFM/ton of an HVAC system can be increased to more effectively maintain comfortable temperatures in a conditioned space during a peak demand response time while still fulfilling the requirements of an associated demand request (e.g., to operate at a predefined setpoint temperature or at a reduced power consumption). For example, the temperature in a conditioned space may increase less rapidly during a peak demand response time when the efficiency modes described in this disclosure are employed.

HVAC System

FIG.1is a schematic diagram of an embodiment of an HVAC system100configured for operation during a peak demand response time. The HVAC system100conditions air for delivery to a conditioned space. The conditioned space may be, for example, a room, a house, an office building, a warehouse, or the like. In some embodiments, the HVAC system100is a rooftop unit (RTU) that is positioned on the roof of a building and the conditioned air is delivered to the interior of the building. In other embodiments, portion(s) of the system may be located within the building and portion(s) outside the building. The HVAC system may include one or more heating elements, not shown for convenience and clarity. The HVAC system100may be configured as shown inFIG.1or in any other suitable configuration. For example, the HVAC system100may include additional components or may omit one or more components shown inFIG.1.

The HVAC system100includes a working-fluid conduit subsystem102, at least one condensing unit104, an expansion valve114, a cooling unit116, a thermostat132, and a controller136. The HVAC system100is generally configured to operate at an increased sensible capacity when a demand request138is received from third part140which indicates that the HVAC system100is required to operate under conditions associated with decreased power consumption. For example, the demand request138may indicate that the HVAC system100must be operated at a predefined setpoint temperature (e.g., a setpoint temperature that is higher than may be preferred for comfort to occupants of a space conditioned by the HVAC system100) or at a predefined percentage reduction of power consumption during a peak demand response time. In response to the demand request138, the HVAC system100is operated according to an efficiency mode, illustrative examples of which are described in greater detail below, which provides improved cooling during the peak demand response time than was possible using previous technologies, while still satisfying operating requirements associated with the demand request138.

The working fluid conduit subsystem102facilitates the movement of a working fluid (e.g., a refrigerant) through a cooling cycle such that the working fluid flows as illustrated by the dashed arrows inFIG.1. The working fluid may be any acceptable working fluid including, but not limited to, fluorocarbons (e.g. chlorofluorocarbons), ammonia, non-halogenated hydrocarbons (e.g. propane), hydroflurocarbons (e.g. R-410A), or any other suitable type of refrigerant.

The condensing unit104includes a compressor106, a condenser108, and a fan110. In some embodiments, the condensing unit104is an outdoor unit while other components of system100may be indoors. The compressor106is coupled to the working-fluid conduit subsystem102and compresses (i.e., increases the pressure of) the working fluid. The compressor106of condensing unit104may be a variable-speed or multi-stage compressor. A variable-speed compressor is generally configured to operate at different speeds to increase the pressure of the working fluid to keep the working fluid moving along the working-fluid conduit subsystem102. In the variable-speed compressor configuration, the speed of compressor106can be modified to adjust the cooling capacity of the HVAC system100. Meanwhile, a multi-stage compressor may include multiple compressors, each configured to operate at a constant speed to increase the pressure of the working fluid to keep the working fluid moving along the working-fluid conduit subsystem102. In the multi-stage compressor configuration, one or more compressors can be turned on or off to adjust the cooling capacity of the HVAC system100. As described in greater detail below with respect toFIG.5, in certain embodiments, the HVAC system100may include two or more condensing units (e.g., condensing units506and512ofFIG.5).

The compressor106is in signal communication with the controller136using wired or wireless connection. The controller136provides commands or signals to control operation of the compressor106and/or receives signals from the compressor106corresponding to a status of the compressor106. For example, when the compressor106is a variable-speed compressor, the controller136may provide signals to control the compressor speed. When the compressor106operates as a multi-stage compressor, the signals may correspond to an indication of which compressors to turn on and off to adjust the compressor106for a given cooling capacity. The controller136may operate the compressor106in different modes corresponding to load conditions (e.g., the amount of cooling or heating required by the HVAC system100). As described in greater detail below, operation of the compressor106may be adjusted by the controller136before, during, and/or after a peak demand response time to increase the sensible capacity of the HVAC system100during a peak demand response time. The controller136is described in greater detail below with respect toFIG.7.

The condenser108is configured to facilitate movement of the working fluid through the working-fluid conduit subsystem102. The condenser108is generally located downstream of the compressor106and is configured to remove heat from the working fluid. The fan110is configured to move air112across the condenser108. For example, the fan110may be configured to blow outside air through the condenser108to help cool the working fluid flowing there through. The compressed, cooled working fluid flows from the condenser108toward an expansion device114.

The expansion device114is coupled to the working-fluid conduit subsystem102downstream of the condenser108and is configured to remove pressure from the working fluid. In this way, the working fluid is delivered to the cooling unit116and receives heat from airflow118to produce a conditioned airflow120that is delivered by a duct subsystem122to the conditioned space. In general, the expansion device114may be a valve such as an expansion valve or a flow control valve (e.g., a thermostatic expansion valve valve) or any other suitable valve for removing pressure from the working fluid while, optionally, providing control of the rate of flow of the working fluid. The expansion device114may be in communication with the controller136(e.g., via wired and/or wireless communication) to receive control signals for opening and/or closing associated valves and/or provide flow measurement signals corresponding to the rate of working fluid flow through the working fluid subsystem102.

The cooling unit116is generally any heat exchanger configured to provide heat transfer between air flowing through the cooling unit116(i.e., air contacting an outer surface of one or more coils of the cooling unit112) and working fluid passing through the interior of the cooling unit116. For example, the cooling unit116may be or include an evaporator coil. More specifically, the cooling unit116may be or include a row/split intertwined evaporator (e.g., as described in greater detail below with respect toFIG.4) or a face-split evaporator (e.g., as described in greater detail below with respect toFIGS.5and6). The cooling unit116is fluidically connected to the compressor106, such that working fluid generally flows from the cooling unit116to the condensing unit104. A portion of the HVAC system100is configured to move air118across the cooling unit116and out of the duct sub-system122as conditioned airflow120. Return air124, which may be air returning from the building, fresh air from outside, or some combination, is pulled into a return duct126.

A suction side of a blower128pulls the return air124. The blower128discharges airflow118into a duct130such that airflow118crosses the cooling unit116or heating elements (not shown) to produce conditioned airflow120. The blower128is any mechanism for providing a flow of air through the HVAC system100. For example, the blower128may be a constant-speed or variable-speed circulation blower or fan. Examples of a variable-speed blower include, but are not limited to, belt-drive blowers controlled by inverters, direct-drive blowers with electronic commuted motors (ECM), or any other suitable type of blower. The blower128is in signal communication with the controller136using any suitable type of wired or wireless connection. The controller136is configured to provide commands and/or signals to the blower128to control its operation. For example, the controller136may be configured to send signals to the blower128to adjust the speed of the blower128, for example, to increase the cooling capacity of the HVAC system100during a peak demand response time, as described in greater detail below.

The HVAC system100includes one or more sensors130a-bin signal communication with the controller136. The sensors130a-bmay include any suitable type of sensor for measuring air temperature, relative humidity, and/or any other properties of a conditioned space (e.g. a room or building). The sensors130a-bmay be positioned anywhere within the conditioned space, the HVAC system100, and/or the surrounding environment. For example, as shown in the illustrative example ofFIG.1, the HVAC system100may include a sensor130apositioned and configured to measure a return air temperature (e.g., of airflow124) and/or a sensor130bpositioned and configured to measure a supply or treated air temperature (e.g., of airflow120), a temperature of the conditioned space, and/or a relative humidity of the conditioned space. In other examples, the HVAC system100may include sensors positioned and configured to measure any other suitable type of air temperature (e.g., the temperature of air at one or more locations within the conditioned space and/or an outdoor air temperature) or other property (e.g., a relative humidity of air at one or more locations within the conditioned space).

The HVAC system100includes a thermostat132, for example, located within the conditioned space (e.g. a room or building). The thermostat132is generally in signal communication with the controller136using any suitable type of wired or wireless connection. The thermostat132may be a single-stage thermostat, a multi-stage thermostat, or any suitable type of thermostat as would be appreciated by one of ordinary skill in the art. The thermostat132is configured to allow a user to input a desired temperature or temperature setpoint134of the conditioned space for a designated space or zone such as a room in the conditioned space. The controller136may use information from the thermostat132such as the temperature setpoint134for controlling the compressor106and/or the blower128. In some embodiments, the thermostat132includes a user interface for displaying information related to the operation and/or status of the HVAC system100. For example, the user interface may display operational, diagnostic, and/or status messages and provide a visual interface that allows at least one of an installer, a user, a support entity, and a service provider to perform actions with respect to the HVAC system100. For example, the user interface may provide for input of the temperature setpoint134and display of any alerts and/or messages related to the status and/or operation of the HVAC system100.

As described in greater detail below, the controller136is configured to receive a demand request138from a third party140. The demand request138may correspond to information transmitted via an electronic signal from the third party140. Generally, the controller136is configured to receive and interpret the demand request138and to appropriately adjust operation of the HVAC system100to satisfy operating requirements associated with the demand request138. The demand request138is generally associated with a time interval (e.g., a start and stop time) during which certain operating requirements should or must be enforced for the HVAC system100. The time interval of the demand request138may correspond to a peak demand response time (e.g., a time during which electrical power consumption should be decreased). The operating requirements of the demand request138may be associated with a predefined setpoint temperature (i.e., a value at which the temperature setpoint134must be set during the time interval), an amount (e.g., a percentage) by which the HVAC system100must decrease its power consumption, an amount of power that can be consumed by the HVAC system100, or the like. In general, the demand request138may include any appropriate demand requirement associated with decreasing power consumed by the HVAC system100, as would be appreciated by a person skilled in the art. The third party140, which provides the demand request138, may be a utility provider or any other entity with administrative privileges over operation of the HVAC system100.

As described above, in certain embodiments, connections between various components of the HVAC system100are wired. For example, conventional cable and contacts may be used to couple the controller136to the various components of the HVAC system100, including, the compressor106, the expansion valve114, the blower128, sensor(s)130a-b, and thermostat(s)132. In some embodiments, a wireless connection is employed to provide at least some of the connections between components of the HVAC system100. In some embodiments, a data bus couples various components of the HVAC system100together such that data is communicated therebetween. In a typical embodiment, the data bus may include, for example, any combination of hardware, software embedded in a computer readable medium, or encoded logic incorporated in hardware or otherwise stored (e.g., firmware) to couple components of HVAC system100to each other. As an example and not by way of limitation, the data bus may include an Accelerated Graphics Port (AGP) or other graphics bus, a Controller Area Network (CAN) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or any other suitable bus or a combination of two or more of these. In various embodiments, the data bus may include any number, type, or configuration of data buses, where appropriate. In certain embodiments, one or more data buses (which may each include an address bus and a data bus) may couple the controller136to other components of the HVAC system100.

In an example operation of HVAC system100, the HVAC system100starts up to provide cooling to an enclosed space based on temperature setpoint134. For example, in response to the indoor temperature exceeding the temperature setpoint134, the controller136may cause the compressor106and the blower128to turn on to startup the HVAC system100. The HVAC system100is generally operated in a normal cooling mode (e.g., associated with a CFM/ton value in a range from about 400 to 450 CFM/ton or an S/T ratio in a range from about 0.7 to 0.75). Upon receipt of a demand request138, the controller136may determine a start time and operating requirements of the demand request138. For example, the controller may determine, based on the demand request138, that the HVAC system must be operated according to certain energy-saving requirements (e.g., at a particular setpoint temperature or at a particular percentage of the current power consumption) starting at a predefined time in the future and lasting for predefined time interval corresponding to a peak demand response time. The present disclosure contemplates various efficiency modes in which to operate the HVAC system100in order to provide more comfortable (e.g., cooler) temperatures than could be achieved during a peak demand response time using previous technologies. Each efficiency mode generally facilitates operation at an increased sensible capacity while still satisfying the operating requirements associated with the demand request138.

For example, if the demand request138includes a requirement to operate the HVAC system at a predefined setpoint temperature, the controller136may cause the temperature setpoint134to be set to this predefined setpoint temperature. In general, the predefined setpoint temperature is a temperature value that is greater than would generally be preferred for the comfort of individuals occupying a space conditioned by the HVAC system100. For example, in some embodiments, the predefined setpoint temperature is 77° F. or greater. In some embodiments, the controller136may cause the speed of the compressor106to be decreased. The speed of the blower128may then be adjusted to a value based on an efficiency mode CFM/ton value (e.g., to values in a range from about 500-700 CFM/ton, as described with respect to the first efficiency mode illustrated inFIG.3Bbelow) or based on a calculated value (e.g., as described with respect to the second efficiency mode illustrated inFIG.4below). In some embodiments, the controller136may employ a feedback loop to determine and set the speeds of the compressor106and/or blower128based on a measured temperature of the conditioned space (e.g., as also described with respect to the second efficiency mode illustratedFIG.4below). For example, speeds for the compressor106and/or the blower128may be established to increase any one or more of the cooling capacity of the HVAC system100, the efficiency of the HVAC system100, or any other appropriate performance metric of the HVAC system100.

As another example, if the demand request138includes a requirement to operate the HVAC system100at a predefined percentage of current power consumption (e.g., or a predefined percentage of maximum power consumption) for the HVAC system100, the controller136may adjust the speed of the compressor106such that the required percentage of power consumption is obtained. The controller136will further (i.e., while still maintaining the percentage of power consumption required by the demand response138) adjust the speeds of the compressor106and/or blower128to values that achieve an efficiency mode CFM/ton value (e.g., to values in a range from about 500-700 CFM/ton, as described with respect to the first efficiency mode illustrated inFIG.3Bbelow). The speed of the blower128may alternatively be determined and set based on a calculated value and/or via a feedback control loop (e.g., as described with respect to the second efficiency mode illustrated inFIG.4below), while satisfying the required power reduction of the demand request138.

In some embodiments, the cooling unit116includes a face-split evaporator which includes a top circuit positioned above a bottom circuit (e.g., as described with respect toFIG.5below). In such embodiments, the controller136may implement a third efficiency mode of operation and cause, in response to receiving the demand request138, the bottom evaporator circuit to act as an evaporative cooler, for example, by deactivating a compressor associated with this circuit (e.g., a compressor that provides a flow of working fluid through the bottom circuit). As described in greater detail below with respect toFIGS.5and6, deactivating the bottom circuit of the face-split evaporator may provide improved sensible capacity during the demand response time associated with the demand request138.

FIG.2shows an example plot200demonstrating certain benefits of the systems and methods described in this disclosure. The plot200includes values of the percentage of total power consumed202, the CFM/ton value204during normal cooling mode operation of the HVAC system, the corresponding sensible capacity206during cooling mode operation, the adjusted CFM/ton value208during an example efficiency mode operation, and the corresponding sensible capacity210during efficiency mode operation. The total power consumed202generally decreases with decreasing compressor speed. During cooling mode operation, the CFM/ton value204(e.g., or an associated S/T ratio) remains approximately constant at a value near 400 to 450 CFM/ton, and the sensible capacity206decreases relatively sharply with decreasing compressor speed. In contrast, during efficiency mode operation, the CFM/ton value208(e.g., or an associated S/T ratio) is increased, and the corresponding sensible capacity210decreases less rapidly with decreasing compressor speed.

As further illustrated inFIG.2, if a 48% reduction of total power consumption202is enforced by a demand request138, the compressor speed is decreased to an appropriate speed of 30 Hz to achieve this power reduction. The sensible capacity206achieved during normal cooling mode operation at 30 Hz compressor speed decreases by about 42%. Meanwhile, for the same 48% reduction of total power consumption202(i.e., at a compressor speed of 30 Hz), the sensible capacity210during efficiency mode operation only decreases by about 23%. Because the efficiency-mode sensible capacity210is maintained nearer its original value (i.e., with a smaller percent reduction of 23% vs. 48%), efficiency mode operation provides improved cooling compared to that possible using conventional cooling strategies of previous technologies. Since an increase in the sensible capacity is generally associated with a corresponding decrease in latent capacity, in some embodiments, the controller may cause the HVAC system100to operate in a dehumidification mode prior to operating in the various efficiency modes described below (e.g., to help maintain the conditioned space at or near a desired relative humidity value during a peak demand response time).

First Efficiency Mode Operation Based on Operating at a Predefined CFM/Ton Value

FIGS.3A-Bare flowcharts illustrating example methods300,350of operating the HVAC system100ofFIG.1in response to receiving a demand request138. The method300generally includes initial steps which may be performed following receipt of a demand request138and before different process flows are executed based on whether the demand request138is associated with setting a required setpoint temperature (leading to steps316,402, and602ofFIGS.3B,4, and6, respectively) or reducing power consumption (leading to steps334,422, and608ofFIGS.3B,4, and6, respectively). As such, the method300may include preliminary steps that precede any of the methods described in this disclosure including those described with respect toFIGS.3B,4, and6below.

The method300may begin at step302where the controller136determines whether there is an upcoming demand requirement (e.g., a requirement for operating the HVAC system100at a predefined setpoint temperature or at a predefined percentage of power consumption based on a received demand request138). If there is no upcoming demand requirement, the method300may return to start to continue monitoring for an upcoming demand requirement (e.g., based on the receipt of a demand request138).

If an upcoming demand requirement is identified at step302, the controller136determines, at step304, whether to dehumidify the conditioned space prior to the start of the peak demand response time associated with the demand request138. For example, the controller136may receive a relative humidity measurement associated with the conditioned space from sensor130band/or any other sensor of the HVAC system100and determine whether the measured relative humidity is greater than a threshold value. If the relative humidity is greater than the threshold value then pre-dehumidification may be desired at step304, and pre-dehumidification may be performed at step306. At step306, pre-dehumidification may involve operating the HVAC system in a dehumidification mode associated with a relatively low S/T value. For example, the speeds of the compressor106and/or the blower128may be adjusted to operate the HVAC system100at a CFM/ton value that is in a range from about 100 CFM/ton to less than 400 CFM/ton. For example, the CFM/ton value may be adjusted to a value of less than 400 CFM/ton to dehumidify the conditioned space with or without providing substantial cooling to the conditioned space.

At step308, the controller136determines whether the start of the peak demand response time has been reached. The controller136generally continues to wait until this time is reached. After or upon reaching the start of the peak demand response time, the controller136may determine whether the relative humidity (RH) of the conditioned space is less than a maximum relative humidity value (RHmax), at step310. If this criteria is not satisfied, subsequent steps associated with efficiency mode operation may not be performed. This may prevent the conditioned space from becoming excessively or uncomfortably humid during efficiency mode operation.

Otherwise, if the criteria are satisfied at step310, the controller136may proceed to step312to determine whether the demand request138is associated with a requirement to operate at a predefined setpoint temperature. If this is the case, the controller136may proceed to step316,402, or602ofFIGS.3B,4, and6, respectively. If this is not the case, the controller136determines whether the demand request138is associated with operation at a predefined percentage reduction of power at step314. If this is the case, the controller136proceeds to step334,422, and608ofFIGS.3B,4, and6, respectively.

FIG.3Bis a flowchart illustrating an example method350of operating the HVAC system100ofFIG.1in an efficiency mode using a predefined CFM/ton value. Method350may follow from step312or step314ofFIG.3A, based on whether the received demand request138requires operation at predefined setpoint temperature (starting from step312) or a predefined reduction of power consumption (starting from step314), as shown inFIG.3B.

If the demand request138is associated with a requirement to operate the HVAC system100at a predefined setpoint temperature, the method350may begin at step316. At step316, the temperature setpoint134is adjusted to the predefined setpoint temperature associated with the demand request138. For example, the demand request138may be associated with a predefined (e.g., defined by the third party140) setpoint temperature that is a particular value (e.g., 77° F. or greater). In some cases, the predefined setpoint temperature may be provided as an amount to increase the temperature setpoint134. For example, the demand request138may specify a temperature difference value (of about 1 to 10° F.), and the temperature setpoint134may be increased by the temperature difference value. At step316, the speed of the compressor106is also decreased. For example, the compressor106may be adjusted to operate in a low speed mode (e.g., at a speed that is 75% or less of a recommended speed of the compressor106). For example, the low speed mode may correspond to a speed of the compressor106of about 30 Hz or less. The speed of the blower128is adjusted such that the HVAC system100operates at an efficiency mode CFM/ton value. The efficiency mode CFM/ton value is generally larger than the CFM/ton value associated with normal cooling operation (e.g., of about 400 CFM/ton). For example, the efficiency mode CFM/ton value may be in a range from about 500 CFM/ton to about 700 CFM/ton. Operation at an increased CFM/ton value generally corresponds to operation at an increased S/T ratio. Operation at the efficiency mode CFM/ton value may correspond to operation at an S/T ratio of about 0.9 or greater.

At step318, the controller136determines whether a measured temperature (e.g., a temperature of the conditioned space or the temperature of a zone or portion of the conditioned space) is within a predefined range of the new temperature setpoint (Tnew) established at step316. For example, the controller may determine whether the measured temperature is greater than Tnew−1° F. and less than Tnew+0.5° F. (e.g., as shown in the example ofFIG.3B). If the measured temperature is not within this range, the controller136proceeds to step320and determines whether the relative humidity associated with the conditioned space is greater than or equal to the maximum relative humidity value. If the relative humidity value is greater than or equal to the maximum relative humidity value, the controller136proceeds to step322and adjusts the speed of the blower128such that the HVAC system100operates at a normal cooling mode CFM/ton value (e.g., of about 400 to 450 CFM/ton). Operation at the normal cooling mode CFM/ton value may correspond to operation at an S/T ratio in a range from about 0.7 to about 0.75. Otherwise, if the relative humidity value is not greater than or equal to the maximum relative humidity value, the HVAC system100continues to operate according to the efficiency mode associated with step316.

If at step318the measured temperature is within the temperature range associated with this step, the controller136proceeds to step324. At step324, the speed of the compressor106is increased to a medium speed (e.g., in a range from greater than 30 Hz to about 50 Hz), and the speed of the blower128is adjusted such that the HVAC system100continues to operate according to the efficiency mode CFM/ton value (e.g. in a range from about 500 CFM/ton to about 700 CFM/ton). As described above, operation at the efficiency mode CFM/ton value may correspond to operation at an S/T ratio of about 0.9 or greater.

At step326, the controller136determines whether a measured temperature (e.g., a temperature of the conditioned space or the temperature of a zone or portion of the conditioned space) is greater than a threshold temperature (Tthreshold) For example, the threshold temperature may be Tnew+0.5° F. If the measured temperature is not greater than the threshold temperature, the controller136proceeds to step328and determines whether a relative humidity associated with the conditioned space is greater than or equal to the maximum relative humidity value. If the relative humidity is greater than or equal to the maximum relative humidity value, the controller136proceeds to step330and adjusts the speed of the blower128such that the HVAC system100operates at a normal cooling mode CFM/ton value (e.g., of about 400 to 450 CFM/ton). Otherwise, if the relative humidity is not greater than or equal to the maximum relative humidity value, the HVAC system100continues to operate in the efficiency mode associated with step324(i.e., at a medium compressor speed and an efficiency mode CFM/ton value). If at step326the measured temperature is greater than the threshold temperature, the speed of the compressor106is set to a high speed (e.g., a speed greater than 50 Hz, e.g., a speed of 60 Hz, e.g., a maximum recommended speed of the compressor106) at step332. The speed of the blower128is adjusted such that the HVAC system operates at a normal cooling mode CFM/ton value (e.g., of about 400 to 450 CFM/ton).

If the demand request138is associated with a requirement to reduce power consumption, the method350may begin at step334. At step334, the speed of the compressor106is decreased. For example, the compressor106may be adjusted to operate in a low speed mode (e.g., at a speed of about 30 Hz or less). The speed of the blower128is adjusted such that the HVAC system100operates at an efficiency mode CFM/ton value. As described above, the efficiency mode CFM/ton value is generally larger than the CFM/ton value associated with normal cooling operation (e.g., of about 400 to 450 CFM/ton). For example, the efficiency mode CFM/ton value may be in a range from about 500 CFM/ton to about 700 CFM/ton, as described above.

At step336, the controller136determines whether a measured relative humidity associated with the conditioned space is greater than or equal to the maximum relative humidity value. If the relative humidity value is greater than or equal to the maximum relative humidity value, the controller136proceeds to step338and adjusts the speed of the compressor106and the speed of the blower128such that the HVAC system100operates at a normal cooling mode CFM/ton value (e.g., of about 400 to 450 CFM/ton). At step338, the compressor speed may be increased to a medium speed value initially (e.g., a speed in a range from greater than 30 to about 50 Hz) before increasing the speed to a high speed of greater than 50 Hz or at a maximum recommended speed of the compressor106(e.g., at 60 Hz). Otherwise, if at step336the relative humidity value is not greater than or equal to the maximum relative humidity value, the HVAC system100continues to operate according to the efficiency mode associated with step334.

Modifications, additions, or omissions may be made to methods300and350depicted inFIGS.3A-B. Methods300and350may include more, fewer, or other steps. For example, steps may be performed in parallel or in any suitable order. While at times discussed as controller136, HVAC system100, or components thereof performing the steps, any suitable HVAC system or components of the HVAC system may perform one or more steps of the method.

Second Efficiency Mode Operation Based on Calculated CFM/Ton and/or Feedback Control

FIG.4is a flowchart of an example method400of operating the HVAC system100ofFIG.1in an efficiency mode using a calculated CFM/ton value. For example, a CFM/ton value may be calculated according to a relationship that is specific to the HVAC system100such that efficiency and/or sensible capacity can be further improved during peak demand response times. As described in greater detail below, certain steps of method400may be implemented using a feedback control loop418. Method400may start from step312or step314of method300shown inFIG.3Abased on whether the received demand request138requires operation at a predefined setpoint temperature (starting from step312ofFIG.3A) or a predefined reduction of power consumption (starting from step314ofFIG.3A). In some embodiments, the method400may be employed when the cooling unit116of the HVAC system100is a row split/intertwined evaporator.

If the demand request138is associated with a requirement to operate the HVAC system100at a predefined setpoint temperature, the method400may begin from step312ofFIG.3Aat step402. At step402, the temperature setpoint134is adjusted to the predefined setpoint temperature associated with the demand request138. For example, as described above, the demand request138may be associated with a predefined setpoint temperature that is a particular value (e.g., 77° F. or greater). In some cases, the predefined setpoint temperature may be provided via a required increase in the temperature setpoint134. For example, the demand request138may specify a temperature difference value (e.g., of about 1 to 10° F.), and the temperature setpoint134may be increased by the temperature difference value.

At step402, the speed of the compressor106is decreased. For example, the compressor106may be adjusted to operate in a low speed mode (e.g., a speed of about Hz or less). A blower speed is determined based on the compressor speed, and the speed of the blower128is adjusted based on this determined blower speed. For example, the blower speed may be determined using a predefined relationship between blower speed and compressor speed (e.g., a formula, lookup table, or the like). The predefined relationship may facilitate operation at an increased sensible energy efficiency ratio, a preferred (e.g., increased) S/T ratio, or the like. An example of a relationship for determining a blower speed may be: Blower speed=A(compressor speed)2+B(compressor speed)+C, where A, B, and C are constant values. The constants A, B, and C may be specific to the HVAC system100and may be determined, for example, through calibration or other appropriate testing to facilitate operation of the HVAC system100in an efficiency mode which provides increased cooling capacity, efficiency, and/or comfort during a peak demand response time.

At step404, the controller136determines whether a measured temperature (e.g., a temperature of the conditioned space or the temperature of a zone or portion of the conditioned space) is within a predefined range of the new temperature setpoint (Tnew) established at step402. For example, the controller may determine whether the measured temperature is greater than Tnew−1° F. and less than Tnew+0.5° F. (e.g., as shown in the example ofFIG.3B). If the measured temperature is not within this range, the controller136proceeds to step406and determines whether the relative humidity of the conditioned space is greater than or equal to the maximum relative humidity value. If the relative humidity value is greater than or equal to the maximum relative humidity value, the controller136proceeds to step408and adjusts the speed of the blower128such that the HVAC system100operates at a normal cooling mode CFM/ton value (e.g., of about 400 to 450 CFM/ton). Otherwise, if the relative humidity value is not greater than or equal to the maximum relative humidity value, the HVAC system100continues to operate in the efficiency mode associated with step402(i.e., at the decreased compressor speed and the blower speed determined based on the compressor speed).

If at step404the measured temperature is within the temperature range associated with this step, the controller136proceeds to step410. At step410, the compressor106is increased to a medium speed (e.g., in a range from greater than 30 Hz to about 50 Hz), and a new speed is determined for the blower128. For example, the new speed for the blower128may be determined based on a predefined relationship, as described above. The speed of the blower128is adjusted based on this newly determined speed. For example, the speed of the blower128may be adjusted to the determined speed or to a speed within about 5% of the determined speed.

At step412, the controller determines whether a measured temperature (e.g., a temperature of the conditioned space or the temperature of a zone or portion of the conditioned space) is greater than a threshold temperature. For example, the threshold temperature may be Tnew+0.5° F. If the measured temperature is not greater than the threshold temperature, the controller136proceeds to step414and determines whether a relative humidity associated with the conditioned space is greater than or equal to the maximum relative humidity value. If the relative humidity is greater than or equal to the maximum relative humidity value, the controller136proceeds to step416and adjusts the speed of the blower128such that the HVAC system100operates at a normal cooling mode CFM/ton value (e.g., of about 400 to 450 CFM/ton). Otherwise, if the relative humidity is not greater than or equal to the maximum relative humidity value, the HVAC system100continues to operate in the efficiency mode associated with step410(i.e., at a medium compressor speed and a blower speed based on the compressor speed). Returning to step412, if the measured temperature is greater than the threshold temperature, the compressor106is set to a high speed (e.g., a speed greater than 50 Hz), and a speed is determined for the blower128at step420. The speed of the blower128is set based on the determined speed, as described above.

In some embodiments, steps404,410, and412may be implemented in a more continuous manner using a feedback control loop418. For example, proportional-integral (PI) control may be used to implement these steps of the method400such that the speed of the compressor106is gradually adjusted (e.g., increased) during a peak demand response time, based on the measured temperature, and the speed of the blower128is similarly adjusted (e.g., based on a predefined relationship as described above) to a value determined based on the speed of the compressor106. Feedback control loop418may facilitate efficient adjustment of the speed of the compressor106and blower128to provide improved comfort to a conditioned space during a peak demand response time. For example, the feedback control loop418may facilitate operation of the HVAC system100at in increased sensible capacity such that the temperature of a conditioned space may be held at a lower temperature for a greater portion of a peak demand response time than was possible using previous technologies.

If the demand request138is associated with a requirement to reduce power consumption, the method400may begin from step314ofFIG.3Aat step422. At step422, the speed of the compressor106is decreased. For example, the compressor106may be adjusted to operate in a low speed mode (e.g., at a speed of about 30 Hz or less). A speed is determined for the blower128based on the decreased blower speed (e.g., as described above), and/or the speed of the blower128is adjusted based on the determined speed. At step424, the controller136determines whether a measured relative humidity (e.g., a relative humidity of the conditioned space or of a zone of the conditioned space) is greater than or equal to the maximum relative humidity value. If the relative humidity value is greater than or equal to the maximum relative humidity value, the controller136proceeds to step426and adjusts the speed of the compressor106and/or the speed of the blower128such that the HVAC system100operates at a normal cooling mode CFM/ton value (e.g., of about 400 to 450 CFM/ton). For example, the compressor speed may be increased to a medium speed value initially (e.g., a speed in a range from greater than 30 Hz to about 50 Hz) before the speed is gradually increased to a high speed of greater than 50 Hz (e.g., and up to the maximum recommended compressor speed). Otherwise, if the relative humidity value is not greater than or equal to the maximum relative humidity value, the HVAC system100continues to operate according to the efficiency mode associated with step422.

Modifications, additions, or omissions may be made to method400depicted inFIG.4. Method400may include more, fewer, or other steps. For example, steps may be performed in parallel or in any suitable order. While at times discussed as controller136, HVAC system100, or components thereof performing the steps, any suitable HVAC system or components of the HVAC system may perform one or more steps of the method.

Third Efficiency Mode Operation of an HVAC System with a Face-Split Evaporator

In some embodiments, the cooling unit116of the HVAC system100shown inFIG.1is a face-split evaporator.FIG.5shows an illustrative example of a face-split evaporator500. The cooling unit116ofFIG.1may be or include the face-split evaporator500. As shown inFIG.5, the face-split evaporator500includes at least a top evaporator circuit502and a bottom evaporator circuit504. Generally, each of the evaporator circuits502and504is associated with a corresponding condensing unit506and512, respectively. Condensing unit506may include a compressor508and a condenser510, and condensing unit512may include a compressor514and a condenser516. The one or more condensing units104ofFIG.1may include condensing units506and512.

A portion118aof the airflow118ofFIG.1may flow through the top circuit502and exit the top circuit502as cooled airflow portion120a. When airflow portion118aflows through the top circuit502, water vapor from airflow118amay condense on the coils of the top circuit502. At least a portion of this condensed water may fall on the surface (e.g., the surface of coils) of the bottom circuit504. Even when the condensing unit512of the bottom evaporator circuit504is turned off (i.e., when compressor514is turned off), an airflow portion118bof the airflow118may flow through the bottom circuit504and be evaporatively cooled via contact with the water received from the top circuit502. Evaporatively cooled airflow portion120bmay exit the bottom circuit504. Airflow120ofFIG.1may include each of airflows120aand120bofFIG.5.

In some embodiments, the face-split evaporator500is positioned above a drain pan518which captures water falling from the evaporator500(i.e., water not retained on the surface of the bottom circuit504). At least a portion of the water captured in the drain pan518may be absorbed by an air-permeable media520and used to provide further evaporative cooling of airflow portion118b. For example, the media520may be in fluidic contact with the drain pan518via a fluidic connection522or may be inserted directly in a portion of the drain pan518. The fluidic connection522may be a channel, tube, a section of water-absorbing or water-permeable material (e.g., the same material or a different material to that of the air-permeable media520) or any other appropriate element for providing transfer of water from the drain pan518to the media520. At least a portion of airflow118amay flow through media520and contact water on and/or within the media520, thereby providing further evaporative cooling to the airflow portion118band improved cooling to airflow120ofFIG.1, even when the compressor514is turned off to conserve power and satisfy requirements of the demand request138.

FIG.6is a flowchart illustrating example method600of operating the HVAC system100ofFIG.1when the cooling unit116includes the face-split evaporator500ofFIG.5. If the demand request138is associated with a requirement to operate the HVAC system100at a predefined setpoint temperature, the method600may begin from step312ofFIG.3Aat step602. At step602, the temperature setpoint134is adjusted to the predefined setpoint temperature associated with the demand request138(as described above for methods350and400), and the compressor514associated with the bottom evaporator circuit504is turned off. Turning off compressor514allows the bottom evaporator circuit504to act as an evaporative cooler without requiring additional power consumption. For example, water condensate formed on the top evaporator circuit502may fall on the surface of the bottom evaporator circuit504and evaporatively cool airflow118bflowing across the otherwise inactive circuit504, as described above with respect toFIG.5. At step604, the controller determines whether a measured temperature (e.g., a temperature of the conditioned space or the temperature of a zone or portion of the conditioned space) is greater than a threshold temperature. For example, the threshold temperature may be Tnew+0.5° F. If the measured temperature is greater than the threshold temperature, the controller136proceeds to step606and turns on the compressor514associated with the bottom evaporator circuit504.

If the demand request138is associated with a requirement to reduce power consumption, the method600may begin from step314ofFIG.3Aat step608. At step608, the controller136turns off the compressor514associated with the bottom evaporator circuit504, thereby allowing the bottom evaporator circuit504to act as an evaporative cooler without consuming power via operation of compressor514, as described above with respect to step602. If the power consumed by the HVAC system is not decreased sufficiently to satisfy a percentage of power consumption associated with the demand request138, the controller138may further decrease the speed of the compressor508and/or of the blower128. At step610, the controller136determines whether a measured relative humidity is greater than or equal to the maximum relative humidity value. If the relative humidity value is greater than or equal to the maximum relative humidity value, the controller136proceeds to step612and turns on the compressor514associated with the bottom evaporator circuit504and turns on the compressor508associated with the top evaporator circuit502. This facilitates operation at a decreased power consumption as required by the demand request138(i.e., with one compressor turned off), while preventing a further increase in relative humidity by no longer providing for substantial evaporative cooling in the bottom evaporator circuit514, which was facilitated by shutting down the compressor514associated with the bottom evaporator circuit504. Otherwise, if the relative humidity value is not greater than or equal to the maximum relative humidity value, the HVAC system100continues to operate in the efficiency mode with the compressor514turned off.

Modifications, additions, or omissions may be made to method600depicted inFIG.6. Method600may include more, fewer, or other steps. For example, steps may be performed in parallel or in any suitable order. While at times discussed as controller136, HVAC system100, or components thereof performing the steps, any suitable HVAC system or components of the HVAC system may perform one or more steps of the method.

Example Controller

FIG.7is a schematic diagram of an embodiment of the controller136. The controller136includes a processor702, a memory704, and an input/output (I/O) interface706.

The processor702includes one or more processors operably coupled to the memory704. The processor702is any electronic circuitry including, but not limited to, state machines, one or more central processing unit (CPU) chips, logic units, cores (e.g. a multi-core processor), field-programmable gate array (FPGAs), application specific integrated circuits (ASICs), or digital signal processors (DSPs) that communicatively couples to memory704and controls the operation of HVAC system100. The processor702may be a programmable logic device, a microcontroller, a microprocessor, or any suitable combination of the preceding. The processor702is communicatively coupled to and in signal communication with the memory704. The one or more processors are configured to process data and may be implemented in hardware or software. For example, the processor702may be 8-bit, 16-bit, 32-bit, 64-bit or of any other suitable architecture. The processor702may include an arithmetic logic unit (ALU) for performing arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory704and executes them by directing the coordinated operations of the ALU, registers, and other components. The processor may include other hardware and software that operates to process information, control the HVAC system100, and perform any of the functions described herein (e.g., with respect toFIG.3). The processor702is not limited to a single processing device and may encompass multiple processing devices. Similarly, the controller136is not limited to a single controller but may encompass multiple controllers.

The memory704includes one or more disks, tape drives, or solid-state drives, and may be used as an over-flow data storage device, to store programs when such programs are selected for execution, and to store instructions and data that are read during program execution. The memory704may be volatile or non-volatile and may include ROM, RAM, ternary content-addressable memory (TCAM), dynamic random-access memory (DRAM), and static random-access memory (SRAM). The memory704is operable to store one or more setpoints708and threshold values710.

The one or more setpoints708include but are not limited to the temperature setpoint134ofFIG.1. In general, the setpoint(s)708may include any temperature, relative humidity, or other setpoints used to configure cooling or heating functions of the HVAC system100and/or operation of the HVAC system100according to any of the efficiency modes described in this disclosure. For example, the setpoint(s) may include a predefined setpoint temperature received with or as a part of the demand request138. The threshold values710include any of the thresholds used to implement the functions described herein including, for example, the threshold temperatures, maximum relative humidity values, and temperature range values described with respect to the methods ofFIGS.3A-B,4, and6above.

The I/O interface706is configured to communicate data and signals with other devices. For example, the I/O interface706may be configured to communicate electrical signals with components of the HVAC system100including the compressor106, the expansion valve114, the blower128, sensors130a-b, and the thermostat132. For cases where the HVAC system includes a face-split evaporator500(e.g., as described with respect toFIGS.5and6above), the I/O interface706provides communication with compressors508and514. The I/O interface may provide and/or receive, for example, compressor speed signals blower speed signals, temperature signals, relative humidity signals, thermostat calls, temperature setpoints, environmental conditions, and an operating mode status for the HVAC system100and send electrical signals to the components of the HVAC system100. The I/O interface706may include ports or terminals for establishing signal communications between the controller136and other devices. The I/O interface706may be configured to enable wired and/or wireless communications.

While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants note that they do not intend any of the appended claims to invoke 35 U.S.C. § 112(f) as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.