HVAC Controller Setback Calculation Based on Recovery Time
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Solution Overview
Problem
Conventional HVAC control systems rely on linear setback recovery schemes where recovery time is dependent on the difference between setback and setpoint temperatures, offering limited control over energy savings and comfort, as operators have no direct control over the duration of recovery time.
Innovation Solution
An HVAC controller that calculates a setback temperature based on a predetermined recovery time, allowing for independent control of recovery time and dependent calculation of setback temperature, enabling operators to balance comfort and energy savings by determining the setback value as a function of the recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional linear setback recovery schemes are used where recovery time is dependent on the difference between setback and setpoint temperatures, then the system operation is simple, but the operator has no direct control over the duration of recovery time and limited control over energy savings and comfort
Solution Approach 1:
The patent changes the fundamental parameter relationship by making recovery time an independent controllable parameter rather than a dependent variable. The setback calculation module computes setback temperature as a function of user-specified recovery time, inverting the conventional approach where recovery time was determined by temperature differences. This allows direct operator control over recovery duration while maintaining system functionality.
2Measurement precision
If the setback value is calculated as a function of recovery time, then precise control over energy savings and comfort is achieved, but the calculation complexity increases
Solution Approach 1:
The setback calculation module performs self-service by automatically computing the appropriate setback temperature based on the user-specified recovery time and system parameters. Rather than requiring manual calculation or complex user input, the module autonomously determines the optimal setback value, reducing the cognitive burden on operators while providing precise control.
Solution Approach 2:
The system incorporates feedback mechanisms where the controller monitors actual system performance and adjusts setback calculations accordingly. The setback calculation module uses feedback from temperature sensors and system state information to refine setback temperature computations, ensuring accurate achievement of desired recovery times while adapting to changing conditions.
3Reliability
If the system reaches the setpoint temperature within a specified time period, then user comfort is ensured, but energy consumption increases compared to extended recovery periods
Solution Approach 1:
The system dynamically adjusts the setback temperature based on the specified recovery time requirement. Rather than using fixed setback values, the calculation module computes dynamic setback temperatures that optimize the balance between comfort recovery speed and energy consumption. This allows the system to adapt to different user priorities regarding comfort versus energy savings on different occasions.
Data Source
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Figure 2C~3
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AI summary
A system controller of a heating, ventilation and air-conditioning system is configured to control the operation of a demand unit to maintain a comfort characteristic setpoint of a conditioned space. The controller includes a setback calculation module that is configured to calculate a setback value of the setpoint as a function of a recovery time from the setback value to the setpoint.