Technical Field

[0001] The embodiments disclosed herein relate to systems for regulating airflow and temperature control in buildings, and, in particular to a booster fan apparatus, system and methods for increasing the efficiency and efficacy of HVAC systems.

Introduction

[0002] In most residential properties, one or more central heating, ventilation and air-conditioning units (HVACs) are used to send conditioned air through a system of ductwork to rooms or zones in various parts of the structure. Usually, one thermostat controls the temperature of several rooms or zones and in each house, there are at least 2 to 3 areas/rooms that do not have desired temperature and/or airflow due to the bad design or implementation of the ducts which causes weak or insufficient airflow coming from the vents (supply air ducts).

[0003] Often, rooms on the upper floors of a building have significantly higher temperature in the summer than the rooms in the lower floors. In the winter, the opposite happens, and in addition, rooms above the garage of a dwelling usually have lower temperatures than other rooms. In order to solve such problems, there are a few different approaches, for example: redesign and renovations to the HVAC system; blocking some of the vents using a damper in areas with excess airflow, for example in a basement, to direct more airflow to other floors; using conventional booster fans to improve the airflow in areas with less airflow and employing multi-zoning temperature regulation using multiple HVAC units.

[0004] Renovations to existing HVAC systems and the installation of multiple HVAC units can be costly, time consuming, and requires downtime to perform installation/renovations. Similarly, there are drawbacks associated with using dampers. Blocking vents by dampers does not have a significant effect on the air flow in the areas which have the aforementioned issues. In fact, dampers increase the downstream pressure, resulting in more stress on the main blower and may cause some hazardous situations where HVACs become dysfunctional or breakdown. Blocking the airflow may not guarantee directing the airflow to where it is needed. For example, by closing the vents in the basement, there may be more airflow in the main floor but not much change in a bedroom on the second floor.

[0005] Conventional booster fans provide a less costly solution, as they can be installed relatively quickly in areas with less airflow to boost the airflow in those areas. However, there are two major problems with the booster fans: 1 ) conventional booster fans do not work synchronously with the main HVAC unit. To rectify this issue, some conventional booster fan systems use temperature sensors and a low-level decision making unit and control mechanism to set point of thermostats to boost the airflow. However, there is no scientific data to prove or disprove the effectiveness of such methods, and user reviews, show that customer satisfaction seems to be an issue, and as such, industry as well as HVAC manufacturers have generally not adapted such technologies.

[0006] A key limitation of existing booster systems is that analog sensors have a considerable delay in detecting temperature fluctuations and that temperature set point settings may be compromised due to hot or cold air blowing directly to the sensor unit. Furthermore, if the booster fans operate while the main unit is in standby mode, it will result in undesirable situations where rooms receive cold air in the winter and warm air in the summer resulting in further energy inefficiency.

[0007] Accordingly, there is a need for new systems and apparatus to boost the efficiency and efficacy of HVAC systems by addressing the limitations of existing systems.

Summary

[0008] According to an aspect, provided is a booster fan unit for installation in an air duct for increasing the efficiency and efficacy of HVAC systems. The booster fan unit includes a housing having at least one opening and a blower positioned within the opening for moving air through the opening from a first side of the booster fan unit to a second side of the booster fan. The booster fan unit includes at least two retaining arms attached to the housing for retaining the booster fan unit within an air duct adjacent to a register. [0009] The booster fan unit includes a thermistor for measuring the temperature of air passing through the duct, an accelerometer for detecting vibrations during HVAC operation and a microphone for detecting noise of persons in proximity to the booster fan unit.

[0010] The booster fan unit includes a memory for storing processor-executable instructions including an artificial intelligence module and a processor coupled to the memory, wherein upon execution of the instructions by the processor, the booster fan unit is configured to adjust operation of the blower based on inputs received from the thermistor, accelerometer and microphone, and transmit temperature measurements to a mobile device and a backend server for storage and processing.

[0011] The artificial intelligence module comprises one or more machine learning algorithms trained to process inputs received from the thermistor, the accelerometer and the microphone to predict one or more of: an operational state of an HVAC unit; a heat loss index for a room; the presence of persons in the room; and an ambient temperature in the room.

[0012] According to another aspect, there is a method for predicting an operational state of an HVAC unit, the method comprising: measuring temperature over time in an air duct at a frequency of ~40 Hz; determining whether there is a significant difference between a current temperature and a prior temperature, wherein the prior temperature is measured one minute prior to the current temperature; predicting whether the HVAC unit is in a heating cycle, wherein the current temperature is greater than a sum of a heating tolerance parameter and the prior air temperature, and the prior temperature is greater than a heating threshold; predicting whether the HVAC unit is in a cooling cycle, wherein the current temperature is greater than the sum of a cooling tolerance parameter and the prior air temperature, and the prior temperature is less than a cooling threshold; and recording the predicted operational state of the HVAC unit.

[0013] According to another aspect, there is a method for predicting ambient room temperature, comprising: measuring temperature over time in an air duct for at least three qualifying HVAC cycles; calculating a first average linear regression of a slope of a measured temperature curve between the end of each qualifying HVAC cycle to thirty minutes after each qualifying HVAC cycle; calculating a second average linear regression of the slope of the measured temperature curve between thirty minutes after each qualifying HVAC cycle to ninety minutes after each qualifying HVAC cycle; and applying the first and the second average linear regression of the slope to a last temperature measurement to estimate the ambient room temperature.

[0014] Other aspects and features will become apparent, to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments.

Brief Description of the Drawings

[0015] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

[0016] FIG. 1A is a cross-sectional diagram of a system for increasing the efficiency and efficacy of an HVAC, according to an embodiment;

[0017] FIG. 1 B is a diagram of wireless connectivity between components of the system in FIG. 1A;

[0018] FIG. 1 C is a box diagram of the box diagram of the internal components of the booster fan unit in FIGS. 1A-1 B;

[0019] FIG. 2A is a perspective view of a booster fan unit, according to an embodiment; and

[0020] FIG. 2B is a top view of the booster fan unit in FIG. 2A;

[0021] FIG. 2C is the booster fan unit of FIG. 1 A shown installed in a duct in relation to a register;

[0022] FIG. 3 is a flow chart of a method for predicting an operational state of a HVAC unit, according to an embodiment;

[0023] FIG. 4A is an exemplary plot of temperature change over time as during a HVAC heating cycle;

[0024] FIG. 4B is an exemplary plot of temperature change over time during a

HVAC cooling cycle; [0025] FIG. 4C is an exemplary plot of an HVAC cycle for predicting room temperature, according to an embodiment

[0026] FIG. 5A is an exemplary plot showing the effect of increasing air velocity on the temperature measured by a self-heat thermistor; and

[0027] FIG. 5B is an exemplary plot comparing the temperatures recorded by a self-heat thermistor and a digital temperature sensor in a booster fan unit, according to an embodiment.

Detailed Description

[0028] Various apparatuses or processes will be described below to provide an example of each claimed embodiment. No embodiment described below limits any claimed embodiment and any claimed embodiment may cover processes or apparatuses that differ from those described below. The claimed embodiments are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below.

[0029] One or more systems described herein may be implemented in computer programs executing on programmable computer devices, each comprising at least one processor and a data storage system (including volatile and non-volatile memory and/or storage elements). For example, and without limitation, the programmable computer may be a programmable logic unit, a mainframe computer, server, cloud-based program or server, laptop computer, smartphone, or tablet device.

[0030] Each program is preferably implemented in a high-level procedural or object oriented programming and/or scripting language to communicate with a computer system. However, the programs can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language. Each such computer program is preferably stored on a storage media or a device readable by a general or special purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. [0031] A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary a variety of optional components are described to illustrate the wide variety of possible embodiments of the present invention.

[0032] Further, although process steps, method steps, algorithms or the like may be described (in the disclosure and I or in the claims) in a sequential order, such processes, methods and algorithms may be configured to work in alternate orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of processes described herein may be performed in any order that is practical. Further, some steps may be performed simultaneously.

[0033] When a single device or article is described herein, it will be readily apparent that more than one device I article (whether or not they cooperate) may be used in place of a single device I article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be readily apparent that a single device I article may be used in place of the more than one device or article.

[0034] References herein to “conditioned air” means air that has been heated by a furnace or cooled by an air conditioning unit. References herein to “register” means a vent covering or grill that may be opened or closed to regulate the passage of air through a duct.

[0035] Referring to FIG. 1 A, shown therein is a cross-sectional diagram of a system 100 for increasing the efficiency and efficacy of an HVAC system 102, according to an embodiment. The system 100 may be installed in a residential dwelling, or generally, any building having an HVAC system 102 and a network of ducts. Various components of the system 100 may be installed or retrofit to an existing HVAC system 102 having an HVAC unit 104, connected to ducts 106, 107, 108 and registers 109, 110, 111 , 112, 113.

[0036] The HVAC unit 104 is preferably a central (combined) heating, ventilation and air conditioning unit. According to other embodiments, the HVAC unit 104, may be a furnace or an air conditioner unit. The HVAC unit 104 is typically located within a building, for example, in a basement 114 (as shown) or on a floor 116, 118. The HVAC unit 102 may be located on the exterior of the building, for example, on the roof. [0037] The ductwork includes a network of ducts 106, 107, 108 for carrying conditioned air from the HVAC unit 104 to other locations within the building. For example, duct 106 carries conditioned air from the HVAC unit 104 to the basement 114 and a room 116 on a first floor 120. Similarly, duct 107 carries conditioned air from the HVAC unit to a room 118 on a second floor 121. Duct 108 returns air from the rooms 116, 118 back to the HVAC unit 104 for conditioning.

[0038] The system 100 includes one or more booster fan units 122, 123, 124, 125, 126. The booster fan units 122, 123, 124, 125, 126 are installed within the ducts 106, 107, 108 adjacent to the registers 109, 110, 11 , 112, 113. Each booster fan unit includes one or more blowers (i.e. , fans) for either expelling air out of the duct or drawing air into the duct. As shown, certain booster fan units 122, 123 and 126 may be configured for expelling air out of the ducts 106, 107 while other booster fan units 124, 125 are configured for drawing air into the duct 108.

[0039] The booster fan units 122, 123, 124, 125, 126 may be configured for bidirectional blowing, that is, the blowers within the booster fan unit may alternate direction to either expel air out of the duct or draw air into the duct. The booster fan units 122, 123, 124, 125, 126 may include one or more sensors, including an accelerometer, a thermistor (temperature sensor), a pressure sensor and a humidity sensor. According to other embodiments, the sensors may be standalone sensors positioned within the ducts 106, 107, 108 or positioned within the rooms 114, 116, 118. According to some embodiments, the temperature sensor may be a thermostat 128, 129 located within a room 116, 118 and operably connected to the HVAC unit 104.

[0040] The system 100, includes a mobile device 130. The mobile device 130 may be a smartphone, tablet, laptop computer, or the like, having a display, an input interface (e.g., a touchscreen or keyboard) and wireless network components. The mobile device 130 is installed with an application 132 for connecting to the booster fan units 122, 123, 124, 125, 126 over a wireless communications network (FIG. 1 B).

[0041] Referring to FIG. 1 B, shown therein is a diagram of wireless connectivity between certain components of the system in FIG. 1A. As shown, one representative booster fan unit 123, a thermostat 128, the mobile device 130, and a backend server 134 are connected over a wireless communication network 135 (e.g., a Wi-Fi network). The mobile device 130 may also connect directly to the booster fan unit 123 via a Bluetooth connection.

[0042] A user of the mobile device 130 may use the application 132 to connect to and configure the booster fan unit 123. For example, the mobile device 130 may: transmit commands to control the operation of the booster fan unit 123; receive data and sensor readings from the booster fan unit 123; configure the booster fan unit 123 to transmit data and sensor readings to a backend server 134 for storage and/or processing (FIG. 1 B) over the wireless communication network 135; connect multiple booster fan units 123 in a Wi-Fi mesh network; and provide firmware updates to the booster fan unit 123.

[0043] According to some embodiments, the application 132 may be further used to wirelessly connect the booster fan unit 123 to a compatible “smart” thermostat 128 configured for wireless communications. For example, a user may use the application 132 to connect to the thermostat 128 to view the temperature reading of the thermostat and set a desired temperature or temperature range. The thermostat 128 is connected to an HVAC unit (i.e., HVAC unit 10 in FIG. 1A). Accordingly, the user of the mobile device 130 may connect the thermostat 128 to the booster fan unit 123 whereby the booster fan unit 123 receives commands from the thermostat 128 to synchronize the operation of the booster fan unit 123 to an operational state of the HVAC unit.

[0044] The backend server 134 stores historical operational data and sensor measurements received from the booster fan unit 123. For example, the backend server 134 may store the operational time duration of the booster fan unit. A user of the mobile device 130 may use the application 132 to connect to the backend server 134 to view the stored operational data and sensor measurements. The backend server may be further configured to implement artificial intelligence (e.g., a neural network) to model HVAC and booster fan usage patterns using, for example, linear regression analysis, to tune operation of the booster fan for maximum efficiency.

[0045] Referring to FIG. 1 C, shown therein is a box diagram of the internal components of booster fan unit 123 in FIGS. 1A-1 B, according to an embodiment. For brevity and ease of illustration, certain components of the booster fan unit 123 such as the power supply have been omitted.

[0046] The booster fan unit 123 includes wireless network components 156, for example a Wi-Fi transceiver and/or a Bluetooth transceiver, for wireless communication with a mobile device, a thermostat and a backend server (i.e., the mobile device 130, the thermostat 128 and the backend server 134 in FIG. 2B).

[0047] The booster fan unit 123 includes a processor 140 operatively coupled to a memory 142. The memory 142 includes an Al module 144. The Al module 144 comprises a set of processor-executable instructions for controlling operation of the blowers 154 based on inputs received from an accelerometer 150, a microphone 153 and a thermistor 152 as well as commands received from the mobile device, the thermostat or the backend server. The Al module 144 may comprise one or more machine learning algorithms configured to analyze the operation of blowers 123 and the HVAC unit to predict, for example, user preferences/behavior, an operational state of the HVAC unit, resultant airflow and temperature fluctuations and a heat loss index for a given room.

[0048] The accelerometer 150 is configured to detect vibrations in the X-, Y- and Z- axes to determine if/when the HVAC system is operational (i.e., when the HVAC system is turned on or off). For example, when the HVAC system turns on, a resulting vibration in the duct may be detected by the accelerometer. When the HVAC system turns off (or is in standby mode), the reduction (or absence) of vibration may be recorded by the accelerometer 150.

[0049] The thermistor 152 is configured to measure the ambient air temperature, while the blowers are not operating, and a current air temperature while the blowers are in operation. According to some embodiments, the booster fan unit 123 may further include a digital temperature sensor using a heatsink (not shown).

[0050] The measurements recorded by the accelerometer 150 and thermistor 152 may be received by the Al module 144 as inputs to determine an operational state of the HVAC system and control the operation of the blowers 154 accordingly. The recorded measurements may also be wirelessly transmitted to the mobile device or backend server for storage and/or processing. [0051] The microphone 153 detects the sound of people walking or moving in the room where the booster fan unit 123 is installed. The Al module 144 may include instructions to processes the audio signal from the microphone 153 to detect noise above a threshold level indicating the presence of people in the room. In addition, the noise detected by the microphone 153 may be processed by the Al module 144 to adjust operation of the blowers 154 and/or the HVAC system generally, based on the presence/absence of people in the room. For example, the booster fan unit 123 may be configured to only operate while people are present as detected by the microphone 153.

[0052] A second approach to controlling the blowers 154 or HVAC system operation based on the presence/absence of people is by use of the wireless components 156 (i.e., the Bluetooth transceiver) to detect the proximity of Bluetooth devices carried by persons. Detecting the presence of people by proximity of Bluetooth devices may be preferable in areas where ambient noise is high.

[0053] Referring to FIGS. 2A-2C, shown therein are a perspective (FIG. 2A) and a top view (FIG. 2B) of a booster fan unit 200, according to an embodiment; FIG. 2C shows a perspective view of the booster fan unit 200 installed within a duct 250 in relation to a register 260. The booster fan unit 200 may be any of the booster fan units 122, 123, 124, 125, 126 in FIG. 1A.

[0054] The booster fan unit 200 includes a housing 202. The housing 202 holds the internal components of the booster fan unit 200, including one or more sensors, including an accelerometer and/or a thermistor (not shown). The housing 202 is substantially rectangular in shape and sized to fit within a standard (e.g., 3 x 10 inch, 4 x 10 inch, or other standard size) duct 250 (FIG. 2C).

[0055] The booster fan unit 200 includes a port 206 for connecting a power cable (not shown) to power the booster fan unit 200 using an AC power source (e.g., a 120V AC power receptacle). According to some embodiments, the booster fan unit 200 may be connected directly to an electrical panel or junction box by routing the power cable through ductwork. According to other embodiments, the booster fan unit 200 may be configured for wireless power transfer, wherein the booster fan unit 200 includes wireless charging components (e.g., a secondary induction coil) and is installed in a location having corresponding wireless charging components (e.g., a primary induction coil).

[0056] The booster fan unit 202 includes at least one, preferably two blowers 204a,

204b. The blowers 204a, 204b turn in the same direction to either expel air out of the duct or draw air into the duct. The blowers 204a, 204b may operate at variable speeds. The combined action of the blowers 204a, 204b may move air at a rate of ~80 cubic feet per minute (CFM) at maximum output. The blowers 204a, 204b may include baffles or vibration dampers to minimize noise during operation.

[0057] The booster fan unit 200 includes four retaining arms 208 disposed at four corners of the housing 202. The retaining arms 208 are substantially rigid to support the weight of the booster fan unit 200 and securely retain the booster fan unit 200 within the duct 250. The retaining arms 208 include terminal ends 210 that are perpendicular with respect to the longitudinal section of the retaining arms 208. According to some embodiments, the retaining arms 208 may be spring biased to fictionally engage the walls of the duct 250 for retaining the booster fan unit 200 in ceiling or horizontal wall ducts.

[0058] Now referring to FIG. 2C, the terminal ends 210 rest on a lip of the duct 250, or on a surface (i.e. , a floor, ceiling or wall) adjacent to the lip of the duct 250 to position the booster fan unit 200 substantially in the center of the duct. A register 260 may be placed over the terminal ends 210 such that the terminal ends 210 are securely held in place being interposed between the register 260 and the lip of the duct 250.

[0059] According to some embodiments, the terminal ends 210 have openings for screws or other fasteners to securely attached the booster fan unit 210 to the register 260 and/or a surface (i.e., a floor, ceiling or wall) adjacent to the lip of the duct 250. According to other embodiments, the booster fan unit 200 may be permanently attached to the register 260 at the terminal ends 208; or the register 260 may be integral to the booster fan unit 200, replacing the terminal ends 208, as a means of retaining the booster fan unit 200 within the duct 250.

[0060] According to some embodiments, the booster fan unit 200 may further include dampers (not shown) to regulate the flow of air through the register 260. The dampers provide another means for regulating local climate control by restricting the passive flow of air through the duct 250 and register 260 even when the blowers 204a, 204b are not operating. The dampers many also be used to completely close off the register 260 and retain conditioned air within the duct 250 when not needed in a particular room or area.

[0061] Referring back to FIG. 1A, an objective of the present disclosure is to provide a means for local climate control in one or more rooms 114, 116, 118 in a building having a single HVAC unit 104. Local climate control refers to maintaining a specific ambient temperature (or temperature range) across all rooms 114, 116, 118 based on three factors: (1 ) the set temperature vs. actual ambient temperature in each room; (2) an operational status of the HVAC unit 104; and (3) optimization of the operation of the booster fan units 122, 123, 124, 125, 126 within a given room, and between rooms, to synchronize with the operational status of the HVAC unit 104.

[0062] Regarding factor (1 ), the temperature in each room 114, 116, 118 is set by a user by adjusting the thermostat 128, 129 or by entering a set temperature in the application 132 running on the mobile device 130 (which in turn adjusts a “smart” thermostat, if connected). The actual ambient temperature in the room is measured by either the thermostat 128, 129 or a thermistor within the booster fan units 122, 123, 124, 125, 126.

[0063] Regarding factor (2), the operational status of the HVAC unit 104 must first be known in order to synchronously operate the booster fan units 122, 123, 124, 125, 126 to coincide with operation of the HVAC unit for maximum efficiency and efficacy in climate control. For example, if the room 116 needs be cooled, and the HVAC unit 104 is in a heating state, it would be counter-productive for the booster fan unit 123 to operate to expel warm air into the room via duct 106.

[0064] The operational state of the HVAC unit 104 may be known if the thermostat 128, 129 is a “smart” thermostat wirelessly connected to the booster fan units 122, 123, 124, 125, 126. However, if the thermostat 128, 129 is an analog thermostat, or is not connected/out of range of the booster fan units 122, 123, 124, 125, 126), the operational status of the HVAC unit 104 may be predicted to determine whether the HVAC unit 104 is in a cooling or a heating state (see FIG. 3).

[0065] Regarding factor (3), optimization of the operation of the booster fan units 122, 123, 124, 125, 126 may be performed for greater efficiency (less operating time) to achieve a temperature as set by a user according to a room’s “fingerprint” or heat loss index, that is, the rate at which the temperature in the rooms 114, 116, 118 change due to operation of the HVAC unit 104 while the booster fan units 122, 123, 124, 125, 126 in the rooms 114, 116, 118 are off or blowing air at variable speeds. Accordingly, the required air velocity through the registers 109, 110, 111 , 112, 113 to achieve the required temperature change can be estimated (see FIGS. 4A-4C) to determine the when the booster fan units 122, 123, 124, 125, 126 blowers should be turned on and off.

[0066] Also, optimization of booster fan unit 122, 123, 124, 125, 126 run time can avoid unnecessary blower operation when not required. For example, if the thermostats 128, 129 in the rooms 116, 118 are both set to 21 degrees Celsius and the actual temperature is 21 degrees in the room 116 and 19 degrees in the room 118, only booster fan unit 126 need be operational when the HVAC unit 104 is in the heating state to boost warm air through duct 107; whereas the booster fan unit 123 may remain with blowers off since the temperature in the room 116 is already at the set temperature.

[0067] Referring to FIG. 3, shown therein is a flowchart of a method 300 for predicting the operational state of an HVAC unit. The method 300 may be implemented using a representative booster fan unit 123 shown in FIGS. 1A-1 C. For reference, the elements from FIGS. 1A-1 C are shown in parenthesis.

[0068] At 302, a thermistor (152) within a booster fan unit (123) continuously measures the temperature at a sampling frequency of ~40 Hz (20 readings every half second)According to other embodiments, the temperature may be measured by a standalone temperature sensor installed within a duct (106) or a thermostat (128) installed within the room (116) and connected to the booster fan unit (123).

[0069] At 304, The Al module (144) determines whether there is a significant difference (e.g., greater than 5%) between a current temperature (i.e., the latest temperature measurement) and the temperature measured one minute prior. [0070] At 306, if there is no significant difference between the average measured temperature and subsequent temperature measurements, then it is assumed there has been no change to the operational state of the HVAC unit (104) over the duration of the temperature measurements. Accordingly, the operation of the booster fan unit (123) is maintained - that is, if the booster fan unit (123) blowers (154) are on, they remain on; if the booster fans unit (123) blowers (154) are off, they remain off - and the method 300 reverts to Act 302.

[0071] If at 304, if there is a significant difference (for example, greater than 5% difference) between the current measured temperature and temperature measured one minute prior, then the method 300 proceeds to 308.

[0072] At 308, the Al module (144) determines whether the operational state of the HVAC unit is a heating cycle. The HVAC unit is predicted to be in a heating cycle if (1 ) the current temperature difference is greater than the sum of a heating tolerance parameter and the temperature measured one minute prior; and (2) the temperature measured one minute prior is higher than a heating threshold. The heating tolerance parameter (e.g., 0.3 degrees Celsius) and the heating threshold (e.g., 25 degrees Celsius) are specific to the environment/room and may be set by a user. If the Al module (144) predicts that the HVAC unit (104) is in a heating cycle, booster fan unit (123) blowers (154) are turned on (if they are not already on) at Act 312.

[0073] At 310, the Al module (144) determines whether the operational state of the HVAC unit is a cooling cycle. The HVAC unit is predicted to be in a cooling cycle if (1 ) the current temperature is greater than the sum of a cooling tolerance parameter and the temperature measured one minute prior; and (2) the temperature measured one minute prior is less than a cooling threshold. The cooling tolerance parameter (e.g., 0.4 degrees Celsius) and the cooling threshold (e.g., 22 degrees Celsius) are specific to the environment/room and may be set by a user. If the Al module (144) predicts that the HVAC unit (104) is in a cooling cycle, the booster fan unit (123) blowers (154) are turned on (if they are not already on) at Act 314.

[0074] At 316, the predicted state (either a heating cycle or a cooling cycle) of the HVAC unit (104) is recorded and the method 300 reverts to Act 302. Since temperature measurements are continuously recorded at act 302, the predicted state of the HVAC unit may be dynamically predicted and recorded, in near-real time. Similarly, the duration of an HVAC cycle (i.e. , the duration of time the HVAC unit is in actual operation), whether in a predicted heating cycle or a predicted cooling cycle, is continuously assessed and recorded. The predicted state of the HVAC unit (104) may be transmitted by the booster fan unit (123) to the backend server (134) for storage and to determine a prediction history average.

[0075] At 318, a prediction history average (PHA) for the HVAC unit (104) is determined to establish what state the HVAC is actually in, to account for potentially incorrect heating or cooling cycle predictions. To avoid (or minimize) incorrect predictions, the PHA is determined by only considering HVAC cycles lasting 5 minutes (300 seconds) or longer. That is, the PHA is calculated using only predicted heating or cooling cycles lasting 5 minutes or longer (and using temperature measurements taken while the HVAC unit was operating for 5 minutes or longer). Given that temperature measurements are continuously recorded at Act 302, measurements taken during HVAC cycles lasting less than 5 minutes, and measurements taken while the HVAC is not operating, are not considered when calculating the PHA. The PHA may be a running average that is updated after completion of the latest heating or cooling cycle lasting 5 minutes or longer.

[0076] The PHA is calculated as follows. If a heating cycle longer than 5 minutes was predicted by successive rounds of Acts 302-304-308-312, a prediction history sum is increased by one (1 ). If a cooling cycle longer than 5 minutes was predicted by successive rounds of Acts 302-304-308-310-314, the prediction history sum is decreased by one (1 ). The PHA is then equal to the prediction history sum divided by the total number of predicted heating and cooling cycles lasting longer than 5 minutes. A positive PHA establishes that the actual HVAC state is a heating state. Conversely, a negative PHA establishes that the actual HVAC state is a cooling state. Accordingly, the season (time of year) may be predicted based on the PHA of the HVAC unit. For example, an average cooling state may be indicative of the summer season and an average heating state may be indicative of the winter season. [0077] To further improve the accuracy in predicting the operational state of the HVAC unit, the accelerometer Al module (144) of the booster fan unit (123) may be configured to constantly process inputs from the accelerometer (150) to detect normal changes in vibration patterns within the ducts, that are indicative of one operational state, or another, to form a “second opinion” to confirm the operational state as determined by the method 300. A sudden or unexpected change in the detected vibration patterns at the vent may be an indication that there is a mechanical issue related to either the HVAC fan bearing or that joints/fixtures in the ducts are loosening.

[0078] Referring to FIG. 4A, shown therein is an exemplary plot 400 of temperature change over time for an HVAC heating cycle, as measured by a thermistor sensor within a booster fan unit itself installed in a duct. Line 402 represents the HVAC operational status (On/Off) (i.e., the blower within the HVAC unit forcing air through the ducts). Curve 404 shows the temperature measured by the thermistor within the booster fan unit. Line 403 shows the desired temperature set point.

[0079] The HVAC heating cycle is from ti until ts lasting approximately 40 minutes. The HVAC commences operation at times ti and ceases operation at ts, respectively. During the initial operation of the HVAC blower between ti and ts, the thermistor experiences a “wind chill” cooling effect of residual cool air from the duct being blown over the thermistor, corresponding to a negative slope of line 404 between ti and t2. Additionally, as air velocity in the duct increases due to operation of the HVAC blower, the self-heat temperature of the thermistor will drop (see FIGS. 5A-5B) further contributing to the wind chill effect between ti and ts.

[0080] From t2 until te, the temperature measured by the thermistor increases due to the now warm air passing through the ducts from the HVAC corresponding to a positive slope between t2 until te. It should be noted that the temperature measured by the thermistor is the temperature within the duct, near the duct opening where the booster fan unit is installed, not the ambient temperature within the room the duct is expelling air to. Generally, the actual temperature increase within the room will be somewhat slower than the measured temperature increase within the duct. Thus, the peak temperature measured within the duct will generally reach higher temperatures than the temperature set point so that the ambient temperature in the room rises faster to reach the temperature set point. If the measured temperature rise within the duct is less than 20-30 degrees Celsius five minutes after the heating cycle commences at ti , it may be indicative of the furnace in the HVAC not functioning properly and/or an issue with the gas supply to the furnace.

[0081] Following the end of the HVAC heating cycle at ts, the air temperature within the duct reaches a plateau at te and gradually decreases thereafter. At time tz, the air temperature in the duct drops to the temperature set point. After tz, the temperature of the air in the duct will be lower than the set point. Accordingly, to maximize energy and heating efficiency, the booster fan unit blowers should turn on to expel air into the room (to speed up the rate at which the room warms up) at ts, just following the increase in the measured temperature and positive slope of line 404, coinciding with the arrival of warm air at the duct opening. The booster fan blowers should cease operation when the air temperature in the duct reaches the set point, since thereafter, the temperature of air in the duct will be below the set point and further expulsion of air from the duct into the room will cause the room temperature to drop. Accordingly, the optimal time duration 406 for operation of the booster fan unit blowers during the HVAC heating cycle is between ts and ty, overlapping with the HVAC heating cycle between ts and te. According to some embodiments, the optimal time duration 406 may be shortened if it is predicted that the room temperature is getting to the desired room temperature before the HVAC operational cycle ends.

[0082] Referring to FIG. 4B, shown therein is an exemplary plot 430 of temperature change over time for several HVAC cooling cycles, as measured by a thermistor sensor within a booster fan unit itself installed in a duct. Line 432 (dashed) represents the HVAC operational status (On/Off) (i.e. , the blower within the HVAC unit forcing air through the ducts). Curve 434 shows the temperature measured by the thermistor within the booster fan unit. Line 436 shows the desired temperature set point.

[0083] A representative HVAC cooling cycle 438 is from ts until tn lasting approximately 6 minutes. During the initial operation of the HVAC blower between ts and tg, the thermistor measures a rise in temperature from residual warm air from the duct being blown over the thermistor, corresponding to a positive slope of line 434 between ts and tg.

[0084] From tg until ti o, the temperature measured by the thermistor decreases due to the now cool air passing through the ducts from the HVAC corresponding to a negative slope of line 434 between tg until ti o after which time the measured temperature plateaus between t and tn. It should be noted that the temperature measured by the thermistor is the temperature within the duct, near the duct opening where the booster fan unit is installed, not the ambient temperature within the room the duct is expelling air to. Generally, the actual temperature decrease within the room will be somewhat slower than the measured temperature decrease within the duct. Thus, the lowest temperature measured within the duct will generally reach lower temperatures than the temperature set point so that the ambient temperature in the room decreases faster to reach the temperature set point. If the measured temperature drop within the duct is less than 5-10 degrees Celsius five minutes after the cooling cycle 438 commences, it may be indicative of the cooling coil in the HVAC not functioning properly and/or the Freon gas pressure in the coil is lower than normal.

[0085] Following the end of the HVAC cooling cycle 438 at tn, the measured air temperature gradually increases. At time ti2, the air temperature in the duct rises to the temperature set point. After ti 2, the temperature of the air in the duct will be higher than the set point. Accordingly, to maximize energy and cooling efficiency, the booster fan unit blowers should turn on to expel air into the room (to speed up the rate at which the room cools down) at tg, just following the decrease in the measured temperature and negative slope of line 434, coinciding with the arrival of cool air at the duct opening. The booster fan blowers should cease operation when the air temperature in the duct reaches the set point, since thereafter, the temperature of air in the duct will be above the set point and further expulsion of air from the duct into the room will cause the room temperature to rise. Accordingly, the optimal time duration 440 for operation of the booster fan unit blowers during the HVAC heating cycle is between tg and ti2, overlapping with the HVAC cooling cycle between tg and tn. [0086] The Al module of the booster fan unit may be configured to optimize operation of the booster fan blowers to maximize energy usage and heating/cooling efficiency by analyzing the temperature change during HVAC heating and cooling cycles as described above with reference to FIGS. 4A and 4B. In addition, the slope (i.e., the rate of change) of the air temperature curves 404, 434 may be used to accurately estimate the ambient temperature within the room. This may be particularly useful in rooms lacking a thermostat.

[0087] Referring to FIG. 4C, shown therein is an exemplary plot 450 of HVAC operational status (dashed line) over time for predicting room temperature, according to an embodiment. The plot 450 shows a first HVAC cycle 452 between ti 3 and ti4, a second HVAC cycle 454 between tis and t and a third HVAC cycle 456 commencing at tie. It is assumed that the ambient room temperature will be equal to the air temperature measured by the thermistor in the booster fan unit (within the duct) at time points before the HVAC cycle commences if there has been no HVAC operation for at least 90 minutes prior to the cycle (e.g., prior to ti 5, given that at least 90 minutes has elapsed between ti 4 and tis), and at least thirty minutes after the end of the HVAC cycle (at least 30 minutes after ti4). For example, the measured temperature at tis is assumed to be equal to the ambient room temperature since the preceding HVAC cycle 452 ended at ti4, at least 90 minutes prior ti 5. Similarly, the measured temperature 30 minutes after ti e is assumed to be equal to the ambient room temperature.

[0088] If at least 90 m inutes has elapsed since the end of the previous HVAC cycle, the ambient room temperature may be estimated as follows. At the start of the HVAC cycle, the ambient room temperature is assumed to be the temperature measured by the booster fan unit thermistor just prior to commencement of the HVAC cycle. For example, at tis the ambient room temperature is assumed to be the air temperature measured by the booster fan unit thermistor a few seconds prior to tis, since 90 minutes has elapsed since the preceding HVAC cycle 454. During the HVAC cycle 456, the ambient room temperature is estimated as described below.

[0089] After conclusion of an HVAC cycle the ambient room temperature is estimated. First, the linear regression of the slope of the temperature curve (i.e., slope of curves 404 and 434 in FIGS. 4A and 4B, respectively) is averaged for at least three qualifying HVAC cycles. A qualifying HVAC cycle is one that has another HVAC cycle preceding it by at least 90 minutes, and is not followed by another HVAC cycle until at least at least 30 minutes after. As shown in FIG. 4C, only HVAC cycle 454 meets the requirements for a qualifying HVAC cycle, the HVAC cycle 454 being preceded by the HVAC cycle 452 90 minutes earlier and followed by the HVAC cycle 456 approximately 70 minutes later.

[0090] A linear regression of the slope of the temperature curve is calculated between the end of a qualifying HVAC cycle to 30 minutes after the qualifying cycle and averaged over at least three qualifying cycles (“Slopeso”). A second linear regression of the slope of the temperature curve is calculated between 30 minutes after the end of the qualifying cycle to 90 minutes after the end of the qualifying cycle and averaged over the same at least three qualifying cycles (“Slopeso to 90”). For an HVAC heating cycle, the ambient room temperature is then estimated by applying the averaged linear regression of slopes to the highest temperature reading (or the lowest temperature reading for a cooling cycle) during the HVAC cycle (i.e. , the last temperature reading recorded before the end of the HVAC cycle, “Ceiling”) according to the following equation: ambient temperature = Slopesoto oo * (Slopeso/ 30 * Ceiling)

[0091] Referring to FIG. 5A, shown therein is an exemplary plot 500 showing the effect of increasing air velocity on the temperature measured by an analog self-heat thermistor. The analog self-heat thermistor may be the thermistor 152 in within the booster fan unit 123 in FIG. 1 C and is exposed to the airflow within the duct. The temperature of the self-heat thermistor will depend on how much heat is dissipated to the surrounding medium (i.e., the air in the duct). As the air flow in the duct increases, the thermistor will dissipate heat better, and its self-heat temperature will drop resulting in higher resistance. The change in resistance can be detected and correlated to the air velocity in the duct.

[0092] The plot 500 shows the dissipation constant of the self-heat thermistor as a function of temperature. As air velocity is increased to a constant value (indicated by line 502), compared to air velocity = 0 (indicated by line 504), the temperature of the self-heat thermistor will drop from T2 to T1 , as shown. The increased air velocity also has the effect of increasing the dissipation constant of the thermistor.

[0093] Using the plot 500, the approximate air velocity within the vent may be determined by how much the thermistor cools and the corresponding air velocity required for the temperature change. For example, a temperature change from T2 to T1 is caused by a constant air velocity, V2. Based on the air velocity, a distance from the duct opening (or the position where the booster fan unit is located) to the furnace, and hence the approximate relative duct branch length may be determined.

[0094] Determining the approximate branch length may be advantageous for mapping a duct network to determine the optimal placement of booster fan units for more efficient heating/cooling. In addition, by mapping the duct network, airflow along longer branches may be better managed when the HVAC system is not operating. For example, longer duct branches are more likely to be connected to more rooms, thus air may be boosted from one room to another room on the same duct branch to “passively” heat/cool rooms when the HVAC system is not operating.

[0095] Another benefit of measuring air velocity within the vent is that a reduction in V2 over time may be indicative of an HVAC air filter becoming clogged or dirty thereby restricting airflow through the ducts and vent. A measured decrease in V2 over 7-10 days may signal that the air filter must be changed to maintain efficiency of the HVAC system.

[0096] Referring to FIG. 5B, shown therein is an exemplary plot 520 comparing the temperatures recorded by an analog self-heat thermistor (grey curve) and a digital temperature sensor (black curve) in a booster fan unit, according to an embodiment. The digital temperature sensor uses a heatsink and is less prone to interference from windchill affecting the recorded temperature. Accordingly, at ti 9, when the HVAC cycle starts, unconditioned residual cool air moving through the duct will cause an initial drop in the temperature measured by both the analog thermistor and digital sensor, however, the effect is more pronounced for the analog thermistor due to the wind-chill effect. Similarly, when the HVAC cycle stops at t2o, the analog thermistor records an initial drop in temperature due to heat dissipation to the moving air around it. [0097] In regions 522, 524 corresponding to time points following the start and end of the HVAC cycle, respectively, the area (gap) between the analog and digital measurement curves represents the air velocity in the duct. The greater the area between the curves, the higher the air velocity in the duct. The air velocity may be calculated by the booster fan unit’s processor using analog and digital temperature measurements as shown in FIG. 5B.

[0098] Referring back to FIG. 1A, the system 100 may be configured to operate in one or more modes. For example, the booster fan units 122, 123, 124, 125, 126 may be configured to operate continuously in an “always on” mode, that is the blowers will always operate regardless of the operational status of the HVAC unit 104 and the ambient and set temperatures within the rooms 114, 116, 118. In an economy mode implementing method 300, the booster fan units 122, 123, 124, 125, 126 may be configured to only operate when the HVAC unit 104 is operating and turn off when the HVAC turns off. In an automatic mode, each room 114, 116, 118 may have a different temperature set point and the booster fan units 122, 123, 124, 125, 126 may be configured to operate only while the HVAC unit 104 is operating and only if the room temperature is not at the set point.

[0099] According to other embodiments, the system 100 may work “passively,” independent of the HVAC unit 104. For example, if the temperature set point in the rooms 116, 118 are both set to 21 degrees Celsius, and the actual ambient temperature in the rooms 116, 118 are 21 degrees and 24 degrees, respectively, the system 100 may be configured to operate booster fan unit 124 to draw relatively cooler air from the room 116 into the duct 108, while booster fan unit 125 operates to expels air from the duct 108 into the room 118. Simultaneously, booster fan unit 126 may operate to drawn relatively warmer air from the room 118 into the duct 107. Accordingly, it is contemplated that any one of booster fan units 122, 123, 124, 125, 126 may be configured for bi-directional blowing to direct air flow to the room 114, 116, 118, where it is needed to meet the temperature set point.

[0100] While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the claims as interpreted by one of skill in the art.