Integrating room space pressure measurements with HVAC controls

Abstract

A substantially tubeless and wireless system accurately measures differential air pressures at several different indoor points relative to outside air. In some embodiments, individual units (e.g., receivers and / or zone transmitters) apply an algorithm to derive the air pressure in the space in which the unit is installed. If the derived pressure is at or near the outside pressure, the unit starts a counter to measure the length of time the equalized pressure condition exists. If the condition persists longer than the time it takes to egress or ingress through a door or to open and close a window, a flag signal is sent to the unit. The unit then takes action to halt cooling or heating in the space. In some embodiments, the unit may be a thermostat, or HVAC controlling device or cloud acting as a HVAC controller. Notification to the end user of the action taken may be provided on the thermostat panel or through a mobile application or other available source.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 639,815, filed Apr. 29, 2024, and titled “Integrating Room Pressure with HVAC Controls,” which is herein incorporated by reference in its entirety.BACKGROUND

[0002] The ability to monitor individual rooms with an understanding of pressure changes relative to outside air pressure provides an opportunity to determine whether windows or doors are open while trying to cool or heat the room. According to some methods, sensors can be installed to detect if a window or door is open. In some examples, a thermostat receives the sensor information from the door and window sensors and then, based on this sensor data, reacts to ambient conditions by turning the air conditioning or heating off as needed. However, each sensor is costly and needs to be installed and integrated with the thermostat so as to permit easy removal and ready battery replacement.SUMMARY

[0003] These and other challenges are addressed by a substantially tubeless and wireless system that accurately measures differential air pressures at several different indoor points relative to outside air. In some embodiments, individual units (e.g., receivers and / or zone transmitters) apply an algorithm to derive the air pressure in the space in which the unit is installed. If the derived pressure is at or near the outside pressure, the unit starts a counter to measure the length of time the equalized pressure condition exists. If the condition persists longer than the time it takes to egress or ingress through a door or to open and close a window, a flag signal is sent to the unit. The unit then takes action to halt cooling or heating in the space. In some embodiments, the unit may be a thermostat, or HVAC controlling device or cloud acting as a HVAC controller. Notification to the end user of the action taken may be provided on the thermostat panel or through a mobile application or other available source.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The following figures, which are incorporated into the form part of this disclosure, illustrate embodiments of the invention and together with the description serve to explain the principals of this invention.

[0005] FIG. 1 shows an example of a communications system that includes a plurality of transmitting units controlled by a receiving unit.

[0006] FIG. 2 shows an example transmitter in block diagram form according to at least one embodiment.

[0007] FIG. 3 illustrates an example of a receiver according to at least one embodiment.

[0008] FIG. 4 illustrates an example of a zeroization method that may be performed by the receiver to calibrate between or among individual absolute pressure sensors to realize a zeroized pressure differential value.

[0009] FIG. 5 illustrates an example of a machine learning algorithm embedded in the receiver that uses CO2 values (ppm) to determine unoccupied periods of time and to provide a zeroization trigger to begin the process of self-calibration by the receiver.

[0010] FIG. 6 illustrates an example state machine for the control logic to the receiver functions for OCCUPIED times.DETAILED DESCRIPTION

[0011] Disclosed here are embodiments of an automated tubeless communicating pressure system that may continuously, periodically, or aperiodically determine air pressure of an indoor space relative to outdoor air pressure (differential pressure) and take action through a unit to turn heating or cooling OFF if the pressure system determines windows or doors are open. The system may include, among other elements, one or more zone transmitting devices capable of Pascal resolution pressure measurement, communication components, a receiver, which may be a thermostat, with a communications component and the ability to influence HVAC climate controls directly through relays or indirectly through cloud based APIs. An outdoor air transmitter is present to measure outside barometric pressure. Each individual receive or zone device receives outside air pressure measurements and resolves individual indoor space pressures independently. The receiving device aggregates the pressure information from the multiple zone transmitters. Action performed by the thermostat is based on if the thermostat is actively cooling or heating the space. The supply fan control, typically the G relay, acts as a trigger to begin monitoring pressure and, if required, take action.

[0012] The receiving device may have a visual display component that alerts users to the condition. In some embodiments, system alerts may be generated and sent to a mobile app or text message. Pre- and post-processing algorithms may be integrated into both transmitters and receivers to determine if the condition is temporary such as a door opening and closing, or if the condition is persistent (e.g., a window is opened and remains so). The receiver device may obtain outside air barometric pressure from a wired sensor, a wireless sensor or an external source such as a cloud interface, for example. This information may be continuously transmitted to all elements in the pressure measurement system. A differential pressure reading is derived from the two absolute pressure readings (indoor and outdoor) to determine if the space is pressurized or at a neutral pressure with respect to the outside air, indicating a door or window is open and causing the space pressure to neutralize. Post processing algorithms and filters may be applied to increase pressure resolution to address noise, prior to being sent to a receiver.

[0013] In some embodiments, an automatic calibration process may be trigged when the space is non-occupied. This can be determined by the schedule in the thermostat or if the CO2 level indicates that there are no people present. Calibration is performed during unoccupied periods. Calibration uses an offset zeroization algorithm introduce to calculate variables into the final derived pressure values. Variables determined during the zeroization process include: production offsets between two sensors, drift introduced over time and altitude differences between the physical placement of the two absolute sensors. Temperature of the sensor membranes is controlled at all times through a modulating pulse width signal with feedback driving a heating element.

[0014] In at least one embodiment, multiple (indoor) zone and outside transmitting devices may communicate wirelessly with a receiver device. Although described as a “wireless transmission” this phrase or word is not intended to be limiting, but would encompass, for example, any signal transmission method including but not limited to Wi-Fi, Lo-Ra, Cellular, BlueTooth, RF in any MHZ, Zigbee, cable, 12C bus, serial and / or directly to an application programming interface for cloud based calculations.

[0015] The transmitters can be battery and / or line voltage operated, and support a visual method to test the communication link and confirm operation. In some embodiments, this testing capability can be installed through an embedded web server running on the transmitter that is accessible through a browser, for example, allowing the testing device to be remote from the transmitter device. However, incorporating the testing capability directly into the transmitter is an example and testing is not limited to such embodiments. In the case that the unit is battery operated, the transmitting device may also contains an audio method to notify the user of low battery or other alert conditions.

[0016] The receiver can be battery and / or line voltage operated. A visual method for an installer to configure the system may be provided by an embedded web server that is accessible through a standard browser, allowing the configuration to be remote from the receiver. Alternatively, or in addition, the configuration device may be incorporated directly into the receiver. In some embodiments, the receiver may provide a visual display to the user that a window or door has been opened or is open.

[0017] Advantages of certain embodiments described herein are numerous and include, without limitation, providing differential pressure measurements between any two points independently and at a low cost by using separate micro-electromechanical (MEMS)-based absolute pressure sensor data to perform the algorithms associated with determining the pressure difference between the areas of interest. A visual indicator of individual space pressure / ventilation characteristics may include both air molecules present based on CO2 molecules and the flow of these air molecules into or out of the space based on positive or negative pressurization. Updating the firmware over the wireless link to provide future capabilities and bug fixes is also possible.

[0018] FIG. 1 shows an example of a communications system 100 that includes a plurality of transmitting units (here, represented by transmitters 31, 32, and 33) controlled by a receiving unit (represented by a receiver 20), although no limit on the number of transmitters or receivers 20 should be inferred. The receiver 20 may be or include a thermostat or an HVAC controller, for example. In some embodiments, the transmitters 31, 32, and / or 33 may be located in different respective indoor spaces or zones, for example in different rooms, with the same receiver 20 acting as a receiver for multiple transmitters. The receiver 20 may receive information regarding outdoor air pressure sensed by a sensor or sensors 10 and communicated to the receiver 20. The outside air pressure may be a reference used by the transmitters to derive differential pressure in the zones in which the transmitters are respectively installed and resolve zone differential pressure relative to the outside. In at least some embodiments, the receiver 20 may be responsible for the retransmission of outside pressure information to one or more of the transmitters 31, 32, and 33. This information can be transmitted to the receiver 20 via a direct wired input or wirelessly over Wi-Fi or other method using UDP broadcast packets, for example.

[0019] The transmitters 31, 32 and 33 may capture transmissions from the receiver 20 to receive outside air information and also the calibration state. In this schematic, each of the individual zones monitored by the transmitters 31, 32, and 33 may transmit their resolved differential pressures in their respective zones. This data may be transmitted in the form of UDP packets over Wi-Fi to the receiver 20. In such embodiments, the receiver 20 may have an internal antenna and be under line power operations. Data received from the transmitters are then used in the control determination algorithm described elsewhere herein.

[0020] FIG. 2 shows an example transmitter 200 in block diagram form according to at least one embodiment. This figure identifies the breakout of hardware logic elements that can perform various functions of the transmitter 200. The transmitter 200 may correspond to one or more of the transmitter devices 31, 32, and 33 of FIG. 1.

[0021] The transmitter 200 may include a power management unit 65, die temperature control logic 61, an ambient noise (fast Fourier transform) filter 55, a differential pressure derivation algorithm unit 60, a zeroization algorithm unit 58, and a visual display filter 59. The transmitter 200 may be operably coupled to receive AC power from a commercial power source via a line conditioning unit 66, and / or DC power from another power source, such as a battery 67. In case the power is received from an AC power source, the line conditioning may include an AC / DC converter, not shown.

[0022] The transmitter 200 may further be operably coupled to one or more sensors related to air quality, examples of which may include one or more of an absolute pressure sensor 52 (which may include or be coupled with a die temperature sensor to adjust for a pressure offset proportional to the temperature of the sensor die), a CO2 sensor 53, and one or more other indoor air quality sensors 54. In some embodiments, output of the absolute pressure sensor 52 (as adjusted according to the die temperature, in some examples) is received by the transmitter 200 via the ambient noise FFT filter 55.

[0023] The absolute pressure sensor 52 and die temperature control logic 61 may be coupled via an ABS temperature control circuit 62. The ABS temperature control circuit 62 may receive output from the absolute pressure sensor 52 and provide the same to the die temperature control logic 61 which operates to adjust the temperature of the die via a heating element to bring the temperature of the die sensor into conformity with a desired temperature programmed into the ABS temperature control sensor 62. An objective of this circuit is to maintain a predetermined die temperature between both the transmitting and receiving sensor membranes, resulting in a more accurate pressure calculation. The die temperature control logic 61 may operate a pulse width modulated control loop that maintains a known and fixed temperature at the sensor membrane. Software filters such as the FFT 55 may be applied to the output of the absolute pressure sensor 52. For example, pressure reading samples between the two disparate sensors are aligned in time to synchronize the measurements, resulting in comparing pressure differences within the sample period. These sample adjustments may take into consideration, for example, any communications delay incurred between getting the readings from the transmitting unit to the receiving unit. Rate of change filters applied to the output “slow” down any transients effects seen in the data from rapid noise injection.

[0024] The transmitter 200 may receive measurements from one or more sensors integrated into the transmitting unit and / or made by a local sensor or sensors associated with the transmitter 20 (e.g., at a site local to the transmitter and in communication with the transmitter), including but not limited to pressure, temperature, and / or humidity, and may wirelessly transmit the data to the receiver 20. The transmitter 200 may have an internal or external antenna, and may be battery or line powered.

[0025] Outside air information, e.g., the outside air pressure, may be re-transmitted from one transmitter to another transmitter or transmitters. For example, in the illustration of FIG. 1, the transmitter 31 may be configured to act as a micro access point for one or more of the transmitters, 32, 33. This allows the transmitter(s) to listen for re-transmission packets specifically from the transmitter 31 over, e.g., a wireless link, and obtain the data being transmitted substantially at the same time as received by the transmitter 31.

[0026] The primary control logic executed by one or more processor(s) may apply the differential pressure derivation algorithm 60 to the received measurement data, store the measurement data in local data storage, and compare the measurement data with its own measurements taken by the absolute pressure sensor, the CO2 sensor, and / or the other indoor air quality sensors according to a time vector to establish a differential pressure between the zone in which the transmitter 200 is located and the outside air. One or more filters may be employed for the user to apply, for example via the user interface, rate of change limits to the output of the pressure sensor data via the communication interface and / or user interface, transmitter sensor data, and derived differential pressure value output. Optionally in accordance with a data averaging filter applied to the space pressure displayed via the visual display filter 59, a value for the differential pressure may be determined and the value may be output and / or transmitted via the user interface or communication interface.

[0027] The power management unit 65 may be embedded in the transmitter 200, and may determine the unit power source—the AC / DC line (via the line conditioning unit 66) or the battery 67, for example—and adapt communications and control operations based on the power configuration. During battery operations, a real-time clock may be used in some embodiments to wake up the transmitter 200 when powered down to save energy, and to anticipate data packets at transmitting unit-based pre-configured time intervals.

[0028] In the case of the transmitter 200, wireless data 57 may be received from the receiver 20 to synchronize calibration of the units and receive outside air pressure readings 51. Primary control stores measurements and compares the measurements with its own measurements 56 using a differential pressure derivation algorithm based on a time vector to establish a differential between sensors. Several filters are available for the user to apply rate of change limits to the output of the pressure sensor data, transmitter sensor data and derived differential pressure value output. Once a value is determined, this can be transmitted 60 to the visual display via the visual display filter 59.

[0029] A control and sensor management module manages the sensor temperature, reliability and data integrity. These functions are performed through the sensor interface hardware and software logic 61 that is operating a pulse width modulated control loop to maintain a known and fixed temperature at the sensor membrane. One or more additional software filters 55 (e.g., an ambient noise filter) may be applied to the derived output from the sensors for out of band readings, rate of change dampening, sample timing filters for data integrity.

[0030] A CO2 sensor 53 and other relevant indoor air quality sensors 54 may be provided to measure, e.g., ambient temperature, humidity, particulates, etc. This data is available to expand the visual display and further refine the algorithms used for the display of ventilation and air quality, for example using machine learning techniques.

[0031] The transmitter embeds a power management module 65 to detect the unit power source—e.g., battery 67 or line 66—and adapt communications and control operations based on the power configuration. For example, during battery operation, a real time clock may be used to wake up the transmitter 200.

[0032] FIG. 3 illustrates an example of a receiver 300 according to at least one embodiment. The receiver 300 may correspond to the receiver 20. The receiver 300 may function at least in part to receive data from one or more of the transmitting devices over a communications link, decode the protocol, and send commands to a control system in the receiver 300 for modifying ambient conditions such as temperature. For example, the control system may turn on or off a heating unit or air conditioning unit to conserve energy when an open door and / or open window is determined based on the pressure differential.

[0033] In some embodiments, the receiver 300 receives measurements, including but not limited to pressure, temperature, humidity, and outside air pressure, from sensors in and / or local to the receiver 300, which may retransmit at least the outside air pressure, e.g., wirelessly, to the transmitters 31, 32, and 33. The receiver 300 may also transmit information, in the form of a UDP packet for example, during a calibration, as described elsewhere herein.

[0034] Because the receiver 300 includes many of the same components as are included in the transmitter 200 and are discussed above (such as the communication interface, user interface, processor(s), memory, and device hardware), such overlapping components will not be described further except to the extent there may be non-negligible differences. FIG. 1 identifies the break out of example hardware logic elements associated with the pressure determination according to at least one embodiment. In some embodiments, the climate control logic in the receiver 300 operates as in the industry standard. The receiver 300 receives power from the Controller chassis.

[0035] In addition to these components, the receiver 300 may include die temperature control logic, an ambient noise FFT filter, a differential pressure derivation algorithm unit 360, a zeroization algorithm unit, a visual display filter 359, and an air quality (AQ) control algorithm unit 370. The receiver 300 may be operably coupled to receive AC power from a commercial power source, e.g., via a line conditioning unit, and / or DC power from another power source, such as a battery. In case the power is received from an AC power source, the line conditioning may include an AC / DC converter.

[0036] The receiver 300 may further be operably coupled to one or more sensors related to air quality, examples of which may include one or more of an absolute pressure sensor (which may include or be coupled with a die temperature sensor to adjust for a pressure offset proportional to the temperature of the sensor die), a CO2 sensor, and one or more other indoor air quality sensors. In some embodiments, output of the absolute pressure sensor (as adjusted according to the die temperature, in some examples) may be received by the receiver 300 via the ambient noise FFT filter.

[0037] As illustrated in FIG. 3, the absolute pressure sensor and die temperature control logic may be coupled via an ABS temperature control circuit. The ABS temperature control circuit may receive output from the absolute pressure sensor and provide the same to the die temperature control logic which operates to adjust the temperature of the die via a heating element to bring the temperature of the die sensor into conformity with a desired temperature programmed into the ABS temperature control sensor. An objective of this circuit is to maintain a predetermined die temperature between both the transmitting and receiving sensor membranes, resulting in a more accurate pressure calculation. More particularly, the control and sensor management unit is configured to manage the sensor power of the absolute pressure sensor, reliability and data integrity. These functions are performed through the die temperature control logic on the receiver 300 operating a pulse width modulated control loop that maintains a known and fixed temperature at the sensor membrane.

[0038] Software filters such as the FFT may be applied to the output of the absolute pressure sensor. In particular, pressure reading samples between the two disparate sensors may be aligned in time to assure that the measurements are synchronized, resulting in comparing pressure differences within a sample period. These sample adjustments may take into consideration, for example, any communications delay incurred between getting the readings from the transmitting unit to the receiving unit. Rate of change filters applied to the output “slow” down any transients effects seen in the data from rapid noise injection.

[0039] As further illustrated in FIG. 3, the primary control logic executed by the processor(s) of the receiver 300 may apply the differential pressure derivation algorithm 360 to the received measurement data, store the measurement data in local data storage, and compare the measurement data with its own measurements taken by the absolute pressure sensor, the CO2 sensor, and / or the other indoor air quality sensors according to a time vector to establish a differential pressure between sensors located in the compared spaces. One or more filters may be employed for the user to apply, for example via the user interface, rate of change limits to the output of the pressure sensor data via the communication interface and / or user interface, transmitting unit sensor data, and derived differential pressure value output. Optionally in accordance with a data averaging filter applied to the space pressure displayed by the visual display filter 359, a value for the differential pressure may be determined and the value may be output and / or transmitted via the user interface or communication interface.

[0040] A visual display can also be provided to indicate measurements and related analysis, including without limitation temperature, real-time space pressure, and CO2 molecule parts per million levels at the sensor site, which could be the location of the transmitter(s) 31, 32, and / or 33 or the receiver 300, or the location of a sensor remote from but in communication with either of these, for example. The visual display may also display differential pressure, e.g., the difference between absolute pressures measured outside and at the transmitter(s) and / or receiver.

[0041] In the case of the receiver 300, air pressure information may be received wirelessly or via a wired bus from one or more of the transmitters 31, 32, and 33 and input as part of the AQ control algorithm 370. Outside air pressure may be received by the receiver 300 from the air pressure sensor 10 either wirelessly or via a wired bus. To synchronize calibration of all air pressure calculating units, the receiver 300 may broadcast the outside air pressure readings to the transmitters 31, 32, and 33. In accordance with a calibration process described elsewhere herein, a calibration command (e.g., flag) can likewise be broadcast by the receiver 300 to the transmitters 31, 32, and 33 during UNOCCUPIED periods of time.

[0042] The output 372 from the receiver 300 may be integrated with standard thermostat, relay, or other HVAC controls to turn off the cooling or heating elements in the thermostat through a control bus or other thermostat control method available. The diagram in FIG. 3 shows the integration to the thermostat chassis over an internal communications bus that controls the standard climate control functions of the thermostat. The internal communications can take other forms suitable to the system design.

[0043] In some embodiments, the visual display on or associated with the receiver 300 may indicate real time indoor space pressure and CO2 molecule content of the various zones in which the transmitters 31, 32, and 33 are located. This visual display may also be used to indicate to the user if action is taken to turn the heat / cool off when pressure conditions indicate an open air situation.

[0044] FIG. 4 illustrates an example of a zeroization method that may be performed by the receiver 300 to calibrate between or among individual absolute pressure sensors to realize a zeroized pressure differential value 88. The absolute pressures may include absolute outdoor air pressure measurement 86 received from the air pressure sensor 10 and absolute indoor air pressure measurement 87 sensed by the absolute pressure sensor of the receiver 300. A periodic zeroization may be performed by the receiver 300 based on ambient and quiescent environmental-UNOCCUPIED-conditions. The zeroization algorithm measures the differences in absolute pressures 86 and 87 during this time and determines a pressure offset term 85. This offset value is constantly calculated during quiet or unoccupied times based on the required values that result in a 0 Pascal set point 89. A rate of change filter may be applied to the derivation of this term. When the receiver 300 transfers into occupied mode, the last offset term 85 is used in the derived pressure calculation to account for product, outside pressure and altitude differences. During OCCUPIED time, the offset term 85 is fixed during all derived pressure calculations.

[0045] Zeroization cycles may be triggered by the CO2 sensor system during an UNOCCUPIED state or at an UNOCCUPIED time. The zeroization method may account for production offsets in the individual sensors, altitude differences between the absolute pressure sensors, and / or drift over time that may occur in a sensor, resulting in a corresponding differential drift between the two differentiated sensors. To counter this, a zeroization may be performed by the receiver 300 when the UNOCCUPIED state of the space being monitored by the receiver 300 has been sensed, at some predetermined time set for the UNOCCUPIED state, or on demand.

[0046] In some embodiments, the zeroization algorithm may receive input of the air pressure values and a calculation is executed by the processor(s) in the receiver 300 to determine one or more offset terms 85 that bring the difference between the two air pressure values at that time to a zero value 89. This offset value(s) 85 (collectively, offset term or offset value) may be based on various factors including, without limitation, production, altitude, and drift offset values, and may be determined in some embodiments according to a machine learning model trained on empirical values. The offset values 85 may be re-calculated during UNOCCUPIED times. In some embodiments, a rate of change filter may be applied to this derivation of this term. When the receiver 300 recognizes a transition into an OCCUPIED state by one of the triggers described herein, the last offset term 85 may be used in the derived pressure calculation to account for production, altitude differences, and drift. During OCCUPIED times, the offset term 85 may be fixed because environmental changes within the occupied space may be so frequent as to likely make calibration ineffective or at least inefficient.

[0047] The detection and adaptation of the algorithm to a crossover condition between, e.g., outdoor air pressure changes from positive to negative relative to the indoor air pressure. This condition can be seen when a low pressure weather event is in the vicinity of the building. The derived differential pressure calculation may be affected, causing the calculation to adjust for this pressure inversion between the independent sensors. This and other embodiments may detect these relative pressure inversions and reflect the same in the measurements set to the display.

[0048] FIG. 5 illustrates an example of a machine learning algorithm embedded in the receiver 300 that uses CO2 values (ppm) to determine unoccupied periods of time and to provide a zeroization trigger to begin the process of self-calibration by the receiver 300. When the receiver 300 transitions from UNOCCUPIED to an OCCUPIED state, the pressure differential derived at the transition time may be used to set the OCCUPIED pressure baseline. The system supply fan (G relay) must also be energized during determination of this value. After the system transitions to OCCUPIED, the occupied pressure baseline is monitored to verify that it is not trending towards a 0 Pascals difference. If this occurs, it will trigger the action condition (e.g., turn on or off the heat or air conditioning). The action taken is based on the thermostat settings.

[0049] The receiver 300 that has the CO2 sensor may continuously monitor CO2 ppm values. During times of stable and lower ppm readings, the receiver 300 may record and average this value to determine a non-occupied CO2 baseline 84. The receiver 300 may send the UNOCCUPIED signal to some or all of the transmitters 31, 32, and 33 during these baselines periods. Self-calibration is to be performed during UNOCCUPIED periods in the space(s) of concern; this process enables the zeroization functions during those periods. In fact, the calibration method of zeroization can be triggered upon determining that the space is UNOCCUPIED. Initial calibration assumes a baseline of 400 ppm in at least one embodiment.

[0050] The UNOCCUPIED state can be based on several factors, taken individually or in combination. For example, an UNOCCUPIED state may be determined on the basis of the CO2 level in the space, a schedule during which time periods are specified or expected to be UNOCCUPIED, observation of the space, and / or other measurables associated with the absence of people. CO2 and / or other levels may be derived directly from a stand-alone CO2 sensor, a CO2 sensor integrated with a thermostat, or received from a cloud or BMS system.

[0051] The trigger may be output in response to a reading by one or more of the other air quality sensors shown in FIG. 3. For example, a CO2 parts per million value may be received from an on-board CO2 sensor (e.g., integral with the receiver 300) or a CO2 sensor coupled to the receiver 300. During times when the CO2 ppm indicates that the space is UNOCCUPIED, as at the shaded region under the baseline 84, the receiver 300 may calibrate using the zeroization method, continuously, periodically, aperiodically, or on demand.

[0052] FIG. 6 illustrates an example state machine for the control logic to the receiver functions for OCCUPIED times.

[0053] In Block 1, the receiver may receive a differential pressure measurement from one or more transmitters. A G relay and / or supply fan are generally active during heating or cooling times. For example, the receiver 300 may receive (continuously or otherwise) derived differential pressures from one or more of the transmitters 31, 32, and / or 33 based on the absolute outside and (indoor) space air pressures as described elsewhere herein. This is received over the wireless communication system as also described elsewhere herein.

[0054] In Block 2, which may occur during block 1, the receiver 300 may calculate its own space pressure (this flow assumes that the receiver 300 and transmitter(s) are in different rooms).

[0055] In Decision Block 3, the processor(s) of the receiver 300 may determine whether any absolute pressure values measured by the receiver 300 and / or transmitter(s) are within a predetermined value of the outside air pressure. For example, the receiver 300 may determine this from the derived differential pressures received from the transmitter(s) (i.e., if any of the derived differential pressures are below a predetermined threshold), or from absolute pressure values that may be received from the transmitter(s) and subtracted from the outside air pressure are processed to determine if they are below the baseline pressure recorded at the transition from OCCUPIED or UNOCCUPIED. If they are at or approaching a neutral or 0 pascal reading, the receiver 300 may transition to Decision Block 4; if not, then the flow may return to Block 1.

[0056] In Decision Block 4, the receiver 300 may determine whether the space HVAC is pressurizing the space. This may be determined by the state of the G relay. If the pressure is at the baseline and not near the baseline within a predetermined value, the receiver 300 may cycle back to Block 1. Pressure measurements may be performed, for example, at a minimum of once every second. If the derived pressure in any of the (indoor) zones or at the receiver 300 is within the deadband for 0 Pascals, the receiver 300 may transition to Decision Block 5.

[0057] In Decision Block 5, the receiver 300 may determine whether cooling or heating is active. This may include determining whether the space is being pressurized by the supply fan and the unit is set to heat or cool. For example, the receiver 300 may determine the state of the Y1, Y2 relays for cooling and the W1, W2 relays for heating. In the case of a heat pump, the O or B relays may be used in this determination. If the HVAC is not actively cooling or heating, the flow may cycle back to Block 1.

[0058] In Block 6, the receiver 300 may determine a period of time in which the space pressure remains at or near (i.e., within a predetermined value of) the outside pressure. Because equal outside and indoor pressures may indicate an open door or window, a wait threshold time period may be set so that a briefly open door or window does not trigger a change in the active state of the receiver (e.g., turning off the heat or air conditioning). If the receiver 300 is in an active heat or cooling cycle, the receiver may start a counter to determine the length of time the space is holding a pressure that is near the outside air pressure. This wait threshold sets up a deadband period of time to be held before any action is taken. For example, this counter may be set initially to five minutes, which can be made subject to change based on characteristics learned from the environment and determined by the pressure system (e.g., frequent outside air pressure changes, very little pressure difference measured over time, regular periods of time in which a particular door or window is opened (e.g., a kitchen window), etc.).

[0059] In Decision Block 7, if the wait threshold is not exceeded (i.e., the space pressure does not fall below the OCCUPIED pressure baseline or rises back to the OCCUPIED pressure baseline after a predetermined time below the wait threshold, such as one minute), the flow may transition back to Block 6.

[0060] In Block 8, if the receiver 300 determines that the wait threshold has been exceeded, the receiver takes action, based on its pressure logic, in the form of turning off the heating or cooling, depending on the mode. The mode may be turned off by de-energizing a relay; however, the supply fan G relay need not be turned off at this time because it may be important that the space continues to be pressurized even if not being heated or cooled.

[0061] In Block 9, the receiver 300 may display a notification of this action on the visual display. Notification of this action can also be sent through text message or otherwise if this capability is present and enabled.

[0062] In Block 10, the receiver 300 may maintain this state and continue to receive derived differential and / or absolute pressure measurements while the heating or cooling is disabled, until the pressure condition changes.

[0063] In Block 11, the receiver 300 may continue to calculate its own space pressure and derive the corresponding differential pressure relative to the outside.

[0064] In Decision Block 12, the receiver 300 monitors space pressure(s) measured by the transmitter(s) for positive pressure differentials. In some instances, all spaces may be under thermostat or other HVAC control by a single receiver 300, in which case the receiver may monitor all spaces to determine when all have returned to positive pressure differential. Positive pressure readings may be subject to a hysteresis to alleviate cycling on the heating or cooling elements. Until positive pressure differential returns in the space or spaces of concern (i.e., NO at Decision Block 12), the flow may return to Block 10. Once positive pressure differential is restored (i.e., YES at Decision Block 12), the receiver 300 may proceed to Block 13.

[0065] In Block 13, the receiver 300 may re-enable heating or cooling, e.g., by re-energizing the relay.

[0066] In Block 14, the receiver 300 may output a notification of the action, e.g., via the visual display, text message, or by another fashion. The receiver 300 then may transition back to Block 1 and continue monitoring.

[0067] If the receiver 300 determines that a space remains UNOCCUPIED for a predetermined period of time, this state machine is exited.

[0068] In an example of monitoring outdoor air quality to maintain indoor conditions, a proactive solution may include monitoring outdoor air quality in real-time and automatically adjusting or closing building input air to limit exposure during poor outside air quality conditions. For example, a system may detect factors such as smoke particulates in the air as well as monitor for the likes of temperature, humidity, CO2, and car exhausts. Traditional economizers and air handlers do not check air quality, but simply open intake dampers to save energy, even when outdoor air is unhealthy.

[0069] In some embodiments of HVAC equipment with motorized input air actuators, a monitor may be installed under the input air hood in the outside air intake. When output from the monitor indicates that outdoor air is considered clean within preset parameters for the various factors being monitored, a control system may open dampers to bring in fresh air for cooling and ventilation, but when output from the monitor indicates that the outdoor air is no within the preset parameters (“unhealthy”), the control system may disable power to the actuator and halt fresh air intake. An alert may be sent out to notify that outside air input has been closed. When the control system, based on output from the monitor, detects improved air conditions within the preset parameters or an alternative set of parameters, normal operation may resume, and an alert may be sent out to notify that the condition is no longer active and outside air input is operating under standard conditions.

[0070] The control system may be integrated with one or more of the embodiments described above. For example, the control system may work in tandem with the receiver 300, or be integrated in the receiver. The control system may provide data based on the monitor output to the receiver 300 and respond to commands from the receiver to perform various functions accordingly, including controlling outside air input and output as indicated. Communications between the control system and receiver may be via physical wire or wireless.

Claims

1. A system, comprising:a plurality of transmitters that respectively comprise:one or more processors;an absolute pressure sensor; andmemory storing computer-readable instructions that, if executed by the one or more processors, cause the one or more processors to perform operations comprising:receiving an outside absolute air pressure;determining a local absolute air pressure;deriving an air pressure differential between the outside absolute air pressure and the local absolute air pressure;transmitting the derived differential pressure to a receiver; andthe receiver that comprises:one or more processors;an absolute pressure sensor; andmemory storing computer-readable instructions that, if executed by the one or more processors, cause the one or more processors to perform operations comprising:receiving the derived differential pressures from the transmitters;comparing the differential pressures to a predetermined threshold;determining whether any of the differential pressures is less than the predetermined threshold;for each differential pressure that is less than the predetermined threshold:determining the time that the differential pressure exists;comparing the time to a wait threshold; andfor any differential pressure that exists for longer than the time threshold, turn off a mode for the space in which the transmitter that supplied the differential pressure is located.

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