Selecting a fallback temperature sensor for no occupancy
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Solution Overview
Problem
HVAC systems face inefficiencies in controlling temperature when determining no occupancy in a building, as they often rely on default temperature sensors that may not accurately represent the entire building's temperature, leading to increased energy costs and comfort issues.
Innovation Solution
A controller that allows users to select a fallback temperature sensor from multiple sensors in the building, enabling it to turn the HVAC system on or off based on the temperature sensed by this selected sensor when the building is unoccupied, thereby optimizing energy usage and comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the HVAC system uses a default temperature sensor (e.g., inside wall-mounted thermostat) to control temperature when no occupancy is detected, then the system operation is simplified, but the temperature control accuracy and representativeness of the entire building's temperature deteriorates
Solution Approach 1:
The system pre-identifies and stores multiple candidate fallback temperature sensors before occupancy status changes. When no occupancy is detected, the controller can immediately switch to using the most appropriate pre-identified sensor, avoiding the need for complex real-time sensor selection while maintaining temperature control accuracy.
Solution Approach 2:
The system introduces an intermediary selection mechanism that identifies which temperature sensor best represents the building's overall temperature condition. This intermediary layer (the selection logic) mediates between the simplicity of using a single default sensor and the accuracy of using multiple sensors, by automatically choosing the most representative sensor based on pre-established criteria.
2Measurement precision
If the HVAC system uses multiple temperature sensors throughout the building, then the temperature measurement coverage and accuracy improve, but the system complexity and cost increase
Solution Approach 1:
The system performs preliminary identification and ranking of temperature sensors during installation or initial configuration, establishing which sensors are most representative of different building zones. This preliminary action allows the system to use multiple sensors effectively without requiring complex real-time analysis, reducing operational complexity while maintaining measurement accuracy.
Solution Approach 2:
The system applies different temperature sensors to different building zones or conditions, with each sensor serving a specific local purpose. The controller selects which sensor to use based on the specific situation (e.g., which zone is most relevant when unoccupied), allowing each sensor to have its own specialized function rather than all sensors performing the same general function.
3Measurement precision
If the HVAC system uses the average temperature of all sensors to control the furnace or AC, then the overall building temperature representation improves, but the responsiveness to specific zone conditions and energy efficiency deteriorates
Solution Approach 1:
The system pre-establishes criteria for selecting the most representative temperature sensor based on factors such as sensor location, building zone importance, and historical temperature data. When no occupancy is detected, the controller uses these pre-established criteria to immediately select the single most relevant sensor, avoiding the energy waste of cooling or heating the entire building when only specific zones matter.
Solution Approach 2:
The system extracts and uses only the temperature data from the single most representative sensor when no occupancy is detected, rather than processing and averaging data from all sensors. This extraction approach eliminates unnecessary processing and enables more aggressive energy-saving operations by focusing on the critical temperature measurement that best represents building conditions.
Data Source
AI summary
In some examples, a method for controlling the heating, ventilation, and air conditioning (HVAC) system in a building includes receiving user input indicating a fallback temperature sensor from a plurality of temperature sensors in the building, the plurality of temperature sensors in the building being associated with a plurality of spaces within the building. The method also includes determining, by the controller, that the plurality of spaces within the building are unoccupied. The method further includes determining, by the controller, a temperature sensed by the fallback temperature sensor based on communication between the controller and the fallback temperature sensor. The method includes causing, by the controller, the HVAC system to turn on or off based on the temperature at the fallback temperature sensor in response to determining that the plurality of spaces within the building are unoccupied.