Method and system for utilizing a bypass humidifier for dehumidification during cooling

An HVAC system includes an indoor heat-exchange coil disposed between a supply air duct and a return air duct. A damper is disposed in a re-circulation duct and is moveable between an open position and a closed position. A controller is configured to determine if the HVAC system is operating in a heating mode or an air-conditioning mode. Responsive to a determination that the HVAC system is operating in the air-conditioning mode, the controller is configured to determine if the variable-speed indoor circulation fan is operating at a minimum speed and if the relative humidity measured by the humidity sensor is above a pre-determined threshold. Responsive to a determination that the variable-speed indoor circulation fan is operating at the minimum speed and the relative humidity of the enclosed space is above the pre-determined threshold, the controller signals the damper to move to the open position.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application incorporates by reference a patent application bearing Ser. No. 16/208/880 and titled METHOD AND SYSTEM FOR SUPPLY-AIR RE-CIRCULATION.

TECHNICAL FIELD

The present disclosure relates generally to heating, ventilation, and air conditioning (HVAC) systems and more particularly, but not by way of limitation, to utilizing a re-circulation duct to utilize a bypass humidifier for dehumidification during cooling.

BACKGROUND

HVAC systems are used to regulate environmental conditions within an enclosed space. Typically, HVAC systems have a circulation fan that pulls air from the enclosed space through ducts and pushes the air back into the enclosed space through additional ducts after conditioning the air (e.g., heating, cooling, humidifying, or dehumidifying the air). To direct operation of the circulation fan and other components, HVAC systems include a controller. In addition to directing operation of the HVAC system, the controller may be used to monitor various components, (i.e. equipment) of the HVAC system to determine if the components are functioning properly.

SUMMARY

Various aspects of the disclosure relate to a heating, ventilation, and air conditioning (HVAC) system. The HVAC system includes an indoor heat-exchange coil disposed between a supply air duct and a return air duct. A re-circulation duct fluidly couples the supply air duct and the return air duct. A damper is disposed in the re-circulation duct and is moveable between an open position and a closed position. A controller operatively coupled to a variable-speed compressor, a variable-speed indoor circulation fan, and the damper. A humidity sensor is disposed in an enclosed space and is configured to measure a relative humidity in the enclosed space. The controller is configured to determine if the HVAC system is operating in a heating mode or an air-conditioning mode. Responsive to a determination that the HVAC system is operating in the heating mode, the controller signals the damper to move to the open position. Responsive to a determination that the HVAC system is operating in the air-conditioning mode, the controller is configured to determine if the variable-speed indoor circulation fan is operating at a minimum speed and if the relative humidity measured by the humidity sensor is above a pre-determined threshold. Responsive to a determination that the variable-speed indoor circulation fan is operating at the minimum speed and the relative humidity of the enclosed space is above the pre-determined threshold, the controller signals the damper to move to the open position. Responsive to a determination that the variable-speed indoor circulation fan is not operating at the minimum speed or the relative humidity of the enclosed space is below the pre-determined threshold, the controller signals the damper to move to the closed position.

Various aspects of the disclosure relate to a heating, ventilation, and air conditioning (HVAC) system. The HVAC system includes a supply air duct, a return air duct, and a re-circulation duct that fluidly couples the supply air duct and the return air duct. A damper is disposed in the re-circulation duct and is moveable between an open position and a closed position. A controller operatively coupled to the damper. A humidity sensor is disposed in an enclosed space and is configured to measure a relative humidity of the enclosed space. The controller is configured to determine if the HVAC system is operating in a heating mode or an air-conditioning mode. Responsive to a determination that the HVAC system is operating in the heating mode, the controller signals the damper to move to the open position. Responsive to a determination that the HVAC system is operating in the air-conditioning mode, the controller is configured to determine if the relative humidity measured by the humidity sensor is above a pre-determined threshold. Responsive to a determination that the relative humidity of the enclosed space is above the pre-determined threshold, the controller signals the damper to move to the open position. Responsive to a determination that the relative humidity of the enclosed space is below the pre-determined threshold, the controller signals the damper to move to the closed position.

Various aspects of the disclosure relate to a method of operating an HVAC system. The HVAC system includes determining, using an HVAC controller, if the HVAC system is operating in a heating mode or an air-conditioning mode. Responsive to a determination that the HVAC system is operating in the heating mode, a damper arranged in a re-circulation duct that fluidly couples a supply air duct to a return air duct is closed. Responsive to a determination that the HVAC system is operating in the air-conditioning mode, damper is closed. In various embodiments, the method includes determining, using the HVAC controller, if a relative humidity of an enclosed space is above a pre-determined threshold. Responsive to a determination that the relative humidity of the enclosed space is not above the pre-determined threshold, the damper is retained in the closed position. Responsive to a determination that the relative humidity of the enclosed space is above the pre-determined threshold, determining using the HVAC controller, if an indoor circulation fan is operating at a minimum speed. Responsive to a determination that the indoor circulation fan is not operating at the minimum speed, the speed of the indoor circulation fan is reduced. Responsive to a determination that the indoor circulation fan is operating at the minimum speed, the damper is opened.

DETAILED DESCRIPTION

Various embodiments will now be described more fully with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

HVAC systems are frequently utilized to adjust both temperature of conditioned air as well as relative humidity of the conditioned air, A cooling capacity of an HVAC system is a combination of the HVAC system's sensible cooling capacity and latent cooling capacity. Sensible cooling capacity refers to an ability of the HVAC system to remove sensible heat from conditioned air. Latent cooling capacity refers to an ability of the HVAC system to remove latent heat from conditioned air. In a typical embodiment, sensible cooling capacity and latent cooling capacity vary with environmental conditions. Sensible heat refers to heat that, when added to or removed from the conditioned air, results in a temperature change of the conditioned air. 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-to-total ratio (“S/T ratio”) is a ratio of sensible heat to total heat (sensible heat+latent heat). The lower the S/T ratio, the higher the latent cooling capacity of the HVAC system for given environmental conditions.

Sensible cooling load refers to an amount of heat that must be removed from the enclosed space to accomplish a desired temperature change of the air within the enclosed space. The sensible cooling load is reflected by a temperature within the enclosed space as read on a dry-bulb thermometer. Latent cooling load refers to an amount of heat that must be removed from the enclosed space to accomplish a desired change in humidity of the air within the enclosed space. The latent cooling load is reflected by a temperature within the enclosed space as read on a wet-bulb thermometer. Setpoint or temperature setpoint refers to a target temperature setting of the HVAC system as set by a user or automatically based on a pre-defined schedule.

When there is a high sensible cooling load such as, for example, when outside-air temperature is significantly warmer than an inside-air temperature setpoint, the HVAC system will continue to operate in an effort to effectively cool and dehumidify the conditioned air. When there is a low sensible cooling load but high relative humidity such as, for example, when the outside air temperature is relatively close to the inside air temperature setpoint, but the outside air is considerably more humid than the inside air, supplemental air dehumidification is often undertaken to avoid occupant discomfort.

An existing approach to air dehumidification involves lowering the temperature setpoint of the HVAC system. This approach causes the HVAC system to operate for longer periods of time than if the temperature setpoint of the HVAC system were set to a higher temperature. This approach serves to reduce both the temperature and humidity of the conditioned air. However, this approach results in over-cooling of the conditioned air, which over-cooling often results in occupant discomfort. Additionally, consequent extended run times cause the HVAC system to consume more energy, which leads to higher utility costs. Another air dehumidification approach involves re-heating of air leaving an evaporator coil.

In HVAC systems having a variable-speed compressor, the compressor speed may be modulated with the cooling load. In an effort to maintain a desirable SIT ratio, a speed of an indoor circulation fan may also be adjusted with the compressor speed. In practice, however, this can be difficult to accomplish as mechanical limitations of the indoor circulation fan establish a minimum possible CFM. Additionally, very low CFM results in poor air distribution within the enclosed space.

FIG. 1illustrates an HVAC system100. In a typical embodiment, the HVAC system100is a networked HVAC system that is configured to condition air via, for example, heating, cooling, humidifying, or dehumidifying air within an enclosed space101. In a typical embodiment, the enclosed space101is, for example, a house, an office building, a warehouse, and the like. Thus, the HVAC system100can be a residential system or a commercial system such as, for example, a roof top system. For exemplary illustration, the HVAC system100as illustrated inFIG. 1includes various components; however, in other embodiments, the HVAC system100may include additional components that are not illustrated but typically included within HVAC systems.

The HVAC system100includes a variable-speed indoor circulation fan110, a gas heat120, electric heat122typically associated with the variable-speed indoor circulation fan110, and an indoor heat-exchange coil130, also typically associated with the variable-speed indoor circulation fan110, The variable-speed indoor circulation fan110, the gas heat120, the electric heat122, and the indoor heat-exchange coil130are collectively referred to as an “indoor unit”148. In a typical embodiment, the indoor unit148is located within, or in close proximity to, the enclosed space101. The HVAC system100also includes a variable-speed compressor140and an associated outdoor heat-exchange coil142, which are typically referred to as an “outdoor unit”144. In various embodiments, the outdoor unit144is, for example, a rooftop unit or a ground-level unit. The variable-speed compressor140and the associated outdoor heat-exchange coil142are connected to an associated indoor heat-exchange coil130by a refrigerant line146. In a typical embodiment, the variable-speed compressor140may be, for example, a single-stage compressor or a multi-stage compressor. The variable-speed indoor circulation fan110, sometimes referred to as a blower, is configured to operate at different capacities (i.e., variable motor speeds) to circulate air through the HVAC system100, whereby the circulated air is conditioned and supplied to the enclosed space101.

Still referring toFIG. 1, the HVAC system100includes an HVAC controller150that is configured to control operation of the various components of the HVAC system100such as, for example, the variable-speed indoor circulation fan110, the gas heat120, the electric heat122, and the variable-speed compressor140to regulate the environment of the enclosed space101, In some embodiments, the HVAC system100can be a zoned system. In such embodiments, the HVAC system100includes a zone controller180, dampers185, and a plurality of environment sensors160. In a typical embodiment, the HVAC controller150cooperates with the zone controller180and the dampers185to regulate the environment of the enclosed space101.

The HVAC controller150may be an integrated controller or a distributed controller that directs operation of the HVAC system100. In a typical embodiment, the HVAC controller150includes an interface to receive, for example, thermostat calls, temperature setpoints, blower control signals, environmental conditions, and operating mode status for various zones of the HVAC system100. For example, in a typical embodiment, the environmental conditions may include indoor temperature and relative humidity of the enclosed space101. In a typical embodiment, the HVAC controller150also includes a processor and a memory to direct operation of the HVAC system100including, for example, a speed of the variable-speed indoor circulation fan110.

Still referring toFIG. 1, in some embodiments, the plurality of environment sensors160are associated with the HVAC controller150and also optionally associated with a user interface170. The plurality of environment sensors160provide environmental information within a zone or zones of the enclosed space101such as, for example, temperature and humidity of the enclosed space101to the HVAC controller150. The plurality of environment sensors160may also send the environmental information to a display of the user interface170. In some embodiments, the user interface170provides additional functions such as, for example, operational, diagnostic, status message display, and 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. In some embodiments, the user interface170is, for example, a thermostat of the HVAC system100. In other embodiments, the user interface170is associated with at least one sensor of the plurality of environment sensors160to determine the environmental condition information and communicate that information to the user. The user interface170may also include a display, buttons, a microphone, a speaker, or other components to communicate with the user. Additionally, the user interface170may include a processor and memory that is configured to receive user-determined parameters such as, for example, a relative humidity of the enclosed space101, and calculate operational parameters of the HVAC system100as disclosed herein.

In a typical embodiment, the HVAC system100is configured to communicate with a plurality of devices such as, for example, a monitoring device156, a communication device155, and the like. In a typical embodiment, the monitoring device156is not part of the HVAC system. For example, the monitoring device156is a server or computer of a third party such as, for example, a manufacturer, a support entity, a service provider, and the like. In other embodiments, the monitoring device156is located at an office of, for example, the manufacturer, the support entity, the service provider, and the like.

In a typical embodiment, the communication device155is a non-HVAC device having a primary function that is not associated with HVAC systems. For example, non-HVAC devices include mobile-computing devices that are configured to interact with the HVAC system100to monitor and modify at least some of the operating parameters of the HVAC system100. Mobile computing devices may be, for example, a personal computer (e.g., desktop or laptop), a tablet computer, a mobile device (e.g., smart phone), and the like. In a typical embodiment, the communication device155includes at least one processor, memory and a user interface, such as a display. One skilled in the art will also understand that the communication device155disclosed herein includes other components that are typically included, in such devices including, for example, a power supply, a communications interface, and the like.

The zone controller180is configured to manage movement of conditioned air to designated zones of the enclosed space101. Each of the designated zones include at least one conditioning or demand unit such as, for example, the gas heat120and at least one user interface170such as, for example, the thermostat. The zone-controlled HVAC system100allows the user to independently control the temperature in the designated zones. In a typical embodiment, the zone controller180operates electronic dampers185to control air flow to the zones of the enclosed space101.

In some embodiments, a data bus190, which in the illustrated embodiment is a serial bus, couples various components of the HVAC system100together such that data is communicated therebetween. In a typical embodiment, the data bus190may 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 the HVAC system100to each other. As an example and not by way of limitation, the data bus190may 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 bus190may include any number, type, or configuration of data buses190, where appropriate. In particular embodiments, one or more data buses190(which may each include an address bus and a data bus) may couple the HVAC controller150to other components of the HVAC system100. In other embodiments, connections between various components of the HVAC system100are wired. For example, conventional cable and contacts may be used to couple the HVAC controller150to the various components. In some embodiments, a wireless connection is employed to provide at least some of the connections between components of the HVAC system such as, for example, a connection between the HVAC controller150and the variable-speed indoor circulation fan110or the plurality of environment sensors160.

FIG. 2is a schematic diagram of the exemplary HVAC system100with a humidity sensor220. For illustrative purposes,FIG. 2will be described herein relative toFIG. 1. In various embodiments, the HVAC system100may operate in a heating mode or an air-conditioning mode. When the HVAC system100is operating in the air-conditioning mode, the HVAC system100may further operate in one of a cooling mode or a dehumidification mode. The HVAC system100includes the indoor heat-exchange coil130, the outdoor heat-exchange coil142, the variable-speed compressor140, and a metering device202. In a typical embodiment, the metering device202is, for example, a thermostatic expansion valve or a throttling valve. The indoor heat-exchange coil130is fluidly coupled to the variable-speed compressor140via a suction line204. The variable-speed compressor140is fluidly coupled to the outdoor heat-exchange coil142via a discharge line206. The outdoor heat-exchange coil142is fluidly coupled to the metering device202via a liquid line208.

Still referring toFIG. 2, during operation, low-pressure, low-temperature refrigerant is circulated through the indoor heat-exchange coil130. The refrigerant is initially in a liquid/vapor state. In a typical embodiment, the refrigerant is, for example, R-22, R-134a, R-410A, R-744, or any other suitable type of refrigerant as dictated by design requirements. Air from within the enclosed space101, which is typically warmer than the refrigerant, is circulated around the indoor heat-exchange coil130by the variable-speed indoor circulation fan110. When the HVAC system operates in the air-conditioning mode, the indoor heat-exchange coil130functions as an evaporator. Thus, the refrigerant begins to boil after absorbing heat from the air and changes state to a low-pressure, low-temperature, super-heated vapor refrigerant. Saturated vapor, saturated liquid, and saturated fluid refer to a thermodynamic state where a liquid and its vapor exist in approximate equilibrium with each other. Super-heated fluid and super-heated vapor refer to a thermodynamic state where a vapor is heated above a saturation temperature of the vapor. Sub-cooled fluid and sub-cooled liquid refers to a thermodynamic state where a liquid is cooled below the saturation temperature of the liquid.

The low-pressure, low-temperature, super-heated vapor refrigerant is introduced into the variable-speed compressor140via the suction line204. In a typical embodiment, the variable-speed compressor140increases the pressure of the low-pressure, low-temperature, super-heated vapor refrigerant and, by operation of the ideal gas law, also increases the temperature of the low-pressure, low-temperature, super-heated vapor refrigerant to form a high-pressure, high-temperature, superheated vapor refrigerant. The high-pressure, high-temperature, superheated vapor refrigerant leaves the variable-speed compressor140via the discharge line206and is directed to the outdoor heat-exchange coil142.

Outside air is circulated around the outdoor heat-exchange coil142by an outdoor fan210. The outside air is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant present in the outdoor heat-exchange coil142. When the HVAC system100is operating in the air-conditioning mode, the outdoor heat-exchange coil142functions as a condenser. Thus, in the air-conditioning mode, heat is transferred from the high-pressure, high-temperature, superheated vapor refrigerant to the outside air. Removal of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state. The high-pressure, high-temperature, sub-cooled liquid refrigerant leaves the outdoor heat-exchange coil142via the liquid line208and enters the metering device202.

Still referring toFIG. 2, when the HVAC system is operating in the heating mode, the direction of refrigerant flow is reversed. Thus, in the heating mode, the indoor heat-exchange coil130functions as a condenser and the outdoor heat-exchange coil142functions as an evaporator. In various embodiments, reversal of refrigerant flow is accomplished by a reversing valve207.

In the metering device202, the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant is abruptly reduced. In various embodiments where the metering device202is, for example, a thermostatic expansion valve, the metering device202reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant by regulating an amount of refrigerant that travels to the indoor heat-exchange coil130. Abrupt reduction of the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant causes sudden, rapid, evaporation of a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant, commonly known as “flash evaporation.” The flash evaporation lowers the temperature of the resulting liquid/vapor refrigerant mixture to a temperature lower than a temperature of the air in the enclosed space101. The liquid/vapor refrigerant mixture leaves the metering device202and returns to the indoor heat-exchange coil130.

Still referring toFIG. 2, the HVAC controller150is operatively coupled to the variable-speed indoor circulation fan110and the variable-speed compressor140. A humidity sensor220is disposed in the enclosed space101and is adapted to measure a relative humidity of the air within the enclosed space101. In various embodiments, the humidity sensor220may be integral with the HVAC controller150. That is, the HVAC controller itself may be disposed in the enclosed space101. In other embodiments, the humidity sensor220may be located remotely from the HVAC controller150and may communicate with the HVAC controller via a wired connection or a wireless protocol. When the HVAC system100is operating in the cooling mode, a speed of the variable-speed compressor140may be adjusted to correspond to changing cooling loads. The HVAC controller150adjusts a speed of the variable-speed indoor circulation fan110relative to a speed of the variable-speed compressor140, Thus, by way of example, a decrease in the speed of the variable-speed compressor140is detected by the HVAC controller150. Communication of the variable-speed compressor140with the HVAC controller150is illustrated inFIG. 2by arrow294. The HVAC controller150then signals the variable-speed indoor circulation fan110to reduce speed. Communication of the HVAC controller150with the variable-speed indoor circulation fan110is illustrated inFIG. 2by arrow272. In certain conditions, however, reduction of the speed of the variable-speed indoor circulation fan110is constrained by mechanical limitations of the variable-speed indoor circulation fan110. Additionally, low speeds of the variable-speed indoor circulation fan110can result in ineffective air distribution throughout the enclosed space101.

FIG. 3is a perspective view of a horizontally aligned supply air duct256and return air duct254.FIG. 4is a perspective view of an upflow supply air duct256and return air duct254. For illustrative purposes,FIGS. 3-4will be described herein relative toFIGS. 1-2. A bypass humidifier301is fluidly coupled to the supply air duct256. A bypass duct302fluidly couples the bypass humidifier301to the return air duct254. Thus, the bypass humidifier301and the bypass duct302fluidly couple the supply air duct256to the return air duct254. A damper304is disposed in the bypass duct302. During operation, the damper304is movable between an open position, which allows air to pass from the supply air duct256, through the bypass humidifier301, through the bypass duct302, and into the return air duct254, and a closed position, which does not allow passage of air through the bypass humidifier301or the bypass duct302. In various embodiments, the damper304is electrically coupled to the HVAC controller150and moves between the open position and the closed position responsive to a signal from the HVAC controller150.

Still referring toFIGS. 3-4, during operation of the HVAC system100in the heating mode, the HVAC controller150signals the damper304to move to the open position. Moving the damper304to the open position allows air to pass from the supply air duct256, through the bypass humidifier301, through the bypass duct302, and into the return air duct254. In various embodiments, the bypass humidifier301includes a wet, evaporative pad303. In various embodiments, a motor-driven fan could be utilized to boost airflow through the bypass duct302. As air passes through the bypass humidifier301, moisture is absorbed into the air from the bypass humidifier301. Thus, the bypass humidifier301increases the relative humidity of the air passing through the HVAC system100during operation of the HVAC system100in the heating mode.

Still referring toFIGS. 3-4, during operation of the HVAC system100in the air-conditioning mode, and particularly, in the cooling mode, the damper304is normally moved to the closed position in an effort to prevent movement or air from the supply air duct256and through the bypass humidifier301. The humidity sensor220monitors a relative humidity of air in the enclosed space101and transmits a signal corresponding to the relative humidity of the enclosed space101to the HVAC controller150. If the humidity sensor220detects a relative humidity in the enclosed space101above a pre-determined threshold, the HVAC controller150transmits a signal to the variable-speed indoor circulation fan110directing the variable-speed indoor circulation fan110to reduce speed in an effort to increase latent capacity of the HVAC system100. If the variable-speed indoor circulation fan110is operating at a minimum rated speed, the HVAC controller150transmits a signal to the damper304directing the damper304to move from the closed position to the open position thereby allowing air to flow from the supply air duct256to the return air duct254via the bypass duct302. In various embodiments, the pre-determined humidity threshold could be, for example, in a range of approximately 40% to approximately 60%; however, in other embodiments, other humidity thresholds could be utilized. In various embodiments, the minimum rated speed of the variable-speed indoor circulation fan110is a manufacturer-established minimum speed based, at least in part, on stability of the variable-speed indoor circulation fan110and power consumption of the variable-speed indoor circulation fan110. In various embodiments, the minimum rated speed of the variable-speed indoor circulation fan110prevents operation of the variable-speed indoor circulation fan110in a speed range that could compromise reliability.

Still referring toFIGS. 3-4, when the damper304is in the open position, a portion of air discharged from the variable-speed indoor circulation fan110travels through the bypass duct302to the return air duct254and is not discharged to the enclosed space101via the supply air duct256. Moving the damper304to the open position reduces a volume of air supplied to the enclosed space101and thus has an effect similar to that of reducing a speed of the variable-speed indoor circulation fan110. Thus, the latent capacity of the HVAC system100is increased and the HVAC system100has better capability to remove moisture from the air. When operating in the air-conditioning mode, a water supply to the bypass humidifier301is turned off in an effort to prevent additional moisture being added to air passing through the bypass duct302. In various embodiments, the evaporative pad may be removed from the bypass humidifier301.

FIG. 5is a flow diagram of a process500for utilizing the bypass duct302. At step504, it is determined if the HVAC system100is operating in air-conditioning mode or heating mode. If at step504, it is determined that the HVAC system is operating in the heating mode, the process500proceeds to step506. At step506, the HVAC controller150signals the damper304to move to the open position. Movement of the damper304to the open position allows air to move from the supply air duct256, through the bypass humidifier301, through the bypass duct302, and into the return air duct254, thereby increasing a relative humidity of the air moving through the HVAC system100during operation of the HVAC system100in the heating mode. From step506, the process500returns to step504. If at step504, it is determined that the HVAC system100is operating in the air-conditioning mode, the process500proceeds to step508. At step508, the HVAC controller150signals the damper304to move to the closed position thereby preventing air from moving through the bypass humidifier301and the bypass duct302. From step508, the process500proceeds to step510.

Still referring toFIG. 5, at step510, the humidity sensor220monitors a relative humidity of the enclosed space101and determines if the relative humidity of the enclosed space101is above the pre-determined threshold. If at step510, it is determined that the relative humidity of the enclosed space101is not above the pre-determined threshold, the HVAC controller150signals the damper304to remain in the closed position. If at step510, it is determined that the relative humidity of the enclosed space101exceeds the predetermined threshold, the process500proceeds to step512. At step512, it is determined if a speed of the variable-speed indoor circulation fan110can be reduced. If at step512, it is determined that the speed of the variable-speed indoor circulation fan110can be reduced, the process500proceeds to step514where the speed of the variable-speed indoor circulation fan110is reduced. From step514, the process500returns to step510. If at step512, it is determined that the speed of the variable-speed indoor circulation fan110cannot be reduced, the process500returns to step506where the HVAC controller150signals the damper304to move to the open position. Moving the damper304to the open position allows air to pass from the supply air duct256, through the bypass humidifier301, through the bypass duct302, and into the return air duct254. Moving the damper304to the open position reduces a volume of air supplied to the enclosed space101and thus has an effect similar to that of reducing a speed of the variable-speed indoor circulation fan110such that the latent capacity of the of the HVAC system100is increased. From step516, the process500returns to step504.

The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms “substantially,” “approximately,” “generally,” and “about” may be substituted with “within 10% of” what is specified.

For purposes of this patent application, the term computer-readable storage medium encompasses one or more tangible computer-readable storage media possessing structures. As an example and not by way of limitation, a computer-readable storage medium may include a semiconductor-based or other integrated circuit (IC) (such as, for example, a field-programmable gate array (FPGA) or an application-specific IC (ASIC)), a hard disk, an HDD, a hybrid hard drive (HHD), an optical disc, an optical disc drive (ODD), a magneto-optical disc, a magneto-optical drive, a floppy disk, a floppy disk drive (FDD), magnetic tape, a holographic storage medium, a solid-state drive (SSD), a RAM-drive, a SECURE DIGITAL card, a SECURE DIGITAL drive, a flash memory card, a flash memory drive, or any other suitable tangible computer-readable storage medium or a combination of two or more of these, where appropriate.

Particular embodiments may include one or more computer-readable storage media implementing any suitable storage. In particular embodiments, a computer-readable storage medium implements one or more portions of the HVAC controller150, one or more portions of the user interface170, one or more portions of the zone controller180, or a combination of these, where appropriate. In particular embodiments, a computer-readable storage medium implements RAM or ROM. In particular embodiments, a computer-readable storage medium implements volatile or persistent memory. In particular embodiments, one or more computer-readable storage media embody encoded software.

In this patent application, reference to encoded software may encompass one or more applications, bytecode, one or more computer programs, one or more executables, one or more instructions, logic, machine code, one or more scripts, or source code, and vice versa, where appropriate, that have been stored or encoded in a computer-readable storage medium. In particular embodiments, encoded software includes one or more application programming interfaces (APIs) stored or encoded in a computer-readable storage medium. Particular embodiments may use any suitable encoded software written or otherwise expressed in any suitable programming language or combination of programming languages stored or encoded in any suitable type or number of computer-readable storage media. In particular embodiments, encoded software may be expressed as source code or object code. In particular embodiments, encoded software is expressed in a higher-level programming language, such as, for example, C, Python, Java, or a suitable extension thereof. In particular embodiments, encoded software is expressed in a lower-level programming language, such as assembly language (or machine code). In particular embodiments, encoded software is expressed in JAVA. In particular embodiments, encoded software is expressed in Hyper Text Markup Language (HTML), Extensible Markup Language (XML), or other suitable markup language.

Depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. Although certain computer-implemented tasks are described as being performed by a particular entity, other embodiments are possible in which these tasks are performed by a different entity.