Method and system for changing a flow rate of air out of a duct in a HVAC system
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Solution Overview
Problem
Existing HVAC fan-forced air register boosters face inefficiencies due to their reliance on thermostatic control, which leads to prolonged operation or premature shutdown, causing nuisance noise and airflow issues, especially when the furnace is not actively running.
Innovation Solution
The system employs a microcontroller-based control method that turns off the booster fan based on the magnitude of deviation between the current duct temperature and stored maximum or minimum temperatures, rather than solely on the deviation from a setpoint, incorporating a conditional sample-and-hold peak detection method to optimize operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the booster fan operates based on a lower setpoint temperature, then the fan turns on sooner after the furnace starts, but the fan continues to operate long after the furnace stops, causing extended run-time and increased noise
Solution Approach 1:
The system uses feedback from temperature sensing to dynamically adjust fan operation. The microcontroller continuously monitors duct temperature and compares it to the setpoint, turning the fan on when the temperature rises above the setpoint and turning it off when the temperature falls below the setpoint, creating a responsive feedback control loop that eliminates both premature shutdown and excessive run-time
Solution Approach 2:
The system changes the operational parameters of the booster fan based on temperature conditions. By using a programmable setpoint that can be adjusted and by comparing current temperature against this parameter, the system optimizes fan operation timing to start sooner and stop earlier, resolving the contradiction between rapid response and excessive run-time
2Duration of action of moving object
If the booster fan operates based on a higher setpoint temperature, then the fan waits several minutes before turning on, but it turns off soon after the furnace stops, causing extended inoperability and reduced airflow
Solution Approach 1:
The feedback control mechanism continuously monitors temperature and immediately responds when the setpoint is exceeded, eliminating the delay in fan activation. The system turns on as soon as the duct temperature rises above the setpoint and turns off when it falls below, ensuring both rapid response and appropriate run-time without the delays caused by higher setpoints
3Productivity
If the booster fan operates against higher static pressure after the furnace stops, then the fan moves duct air without central air handler assistance, but the perceivable fan noise is increased
Solution Approach 1:
The system performs preliminary action by turning off the booster fan before the temperature differential becomes large enough to require high static pressure operation. By using feedback to shut off the fan when the duct temperature falls below the setpoint, the system avoids the noisy high-pressure operation that occurs when the fan runs long after the furnace stops, while still maintaining airflow during the critical period when the furnace is running
Data Source
AI summary
An electric fan powered register booster for a forced air vent in a HVAC system where the booster is configured to stop operation when either of the following events has occurred: 1) the current temperature in the booster has regressed from a recent stored extreme temperature or 2) a predetermined setpoint temperature is between the current temperature and the stored extreme temperature.