HVAC Return Air Control During Space Sensor Data Loss
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Solution Overview
Problem
HVAC systems often fail to operate effectively when sensor data or control device data is unavailable due to communication interruptions or sensor/control device decoupling, leading to unconditioned spaces.
Innovation Solution
The HVAC system employs an alternative operating mode that uses stored or historical data to determine substitute temperature values for both sensed and target temperatures, allowing continuous operation by calculating differences between return air flow temperatures and previously recorded values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the HVAC system operates based on real-time sensor data from the space, then the temperature control accuracy is improved, but the system reliability deteriorates when sensor data is unavailable
Solution Approach 1:
The control system pre-calculates and stores difference values between return air temperature and space temperature during normal operation. When sensor data becomes unavailable, these pre-stored difference values are retrieved and applied to the current return air temperature to estimate the space temperature, enabling continuous operation without real-time space sensors.
Solution Approach 2:
The system uses return air temperature as an intermediary measurement to indirectly determine space temperature when direct space temperature sensing is unavailable. By maintaining a stored difference relationship between return air and space temperatures, the system mediates the lack of direct space temperature data through this intermediate parameter.
2Reliability
If the HVAC system uses multiple sensors and operating modes, then the system reliability is improved during data unavailability, but the device complexity increases
Solution Approach 1:
The control system dynamically switches between primary operating mode (using real-time space temperature sensor data) and alternative operating mode (using stored difference values with return air temperature). This dynamic adaptability allows the system to maintain reliability by selecting the appropriate data source based on availability, without requiring permanently active complex backup systems.
Solution Approach 2:
The system changes the operational parameters by switching between different temperature data sources and calculation methods. In primary mode, it uses direct space temperature readings; in alternative mode, it transforms the approach by using return air temperature plus stored difference values, effectively changing how temperature parameters are obtained and processed.
3Duration of action of stationary object
If the HVAC system stores historical data for alternative operation, then the continuity of operation is improved, but the loss of information increases due to data unavailability
Solution Approach 1:
The control system creates a copy of the temperature difference relationship (return air temperature minus space temperature) and stores it for later use. When original space temperature data is unavailable, this copied difference value is retrieved and applied to current return air temperature to reconstruct the space temperature information, effectively copying the essential thermal relationship for continuity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable operation of HVAC systems during data unavailability periods by maintaining space conditioning based on calculated alternative values, ensuring continuous temperature control.
Implementation Method 1
the HVAC system may place the supply air flow in a heat exchange relationship with a refrigerant of a vapor compression circuit to condition the supply air flow
Data Source
AI summary
A heating, ventilation, and/or air conditioning (HVAC) system includes a conditioning system configured to condition a return air flow directed through the HVAC system and a control system configured to determine a difference value between an operating parameter value of the return air flow and a sensed operating parameter value of a space serviced by the HVAC system, retrieve a stored target operating parameter value of the space, and operate the HVAC system based on the difference value, the stored target operating parameter value, or both.