Economizer cooling delay correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing HVAC systems with economizers face inefficiencies due to inaccurate airflow measurement methods and delayed AC compressor activation, leading to increased energy consumption and reduced thermal comfort.
Innovation Solution
The Fault Detection Diagnostic (FDD) Cooling Delay Correction (CDC) method employs AC Control Temperature (ACT) and High-limit Control Temperature (HCT) to optimize economizer damper positioning and AC compressor operation, correcting delays and faults to enhance cooling capacity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the economizer damper is fully opened to maximize outdoor air cooling, then cooling capacity is improved, but energy consumption increases due to delayed AC compressor activation
Solution Approach 1:
The system performs preliminary action by fully opening the economizer damper in advance when outdoor temperature is favorable, maximizing free cooling capacity before the AC compressor would otherwise be activated. This preliminary economizer operation reduces the cooling load on the AC system and decreases overall energy consumption while maintaining adequate cooling performance
2Temperature
If the AC compressor is activated immediately when outdoor air temperature exceeds the setpoint, then thermal comfort is improved, but energy consumption increases due to unnecessary compression cooling
Solution Approach 1:
The system uses feedback control by continuously monitoring outdoor air temperature and comparing it to the economizer setpoint. When outdoor temperature exceeds the setpoint, the system feedback signals the AC compressor to activate while simultaneously closing the economizer damper. This feedback mechanism ensures the AC compressor operates only when necessary, reducing energy consumption while maintaining indoor temperature stability
Solution Approach 2:
The system applies dynamics by making the economizer damper position dynamic rather than fixed. The damper automatically adjusts its opening degree based on real-time outdoor temperature conditions: fully open when outdoor temperature is below the setpoint (maximizing free cooling), and closed when outdoor temperature exceeds the setpoint (transitions to AC compression cooling). This dynamic adjustment optimizes the balance between cooling capacity and energy consumption
3Reliability
If known airflow measurement methods are used to meet minimum outdoor air requirements, then ventilation standards are satisfied, but measurement accuracy is insufficient leading to reduced thermal comfort
Solution Approach 1:
The system changes the control parameter from fixed minimum outdoor airflow to dynamic outdoor air temperature-based control. Instead of relying on imprecise airflow measurement methods, the system uses accurate temperature sensing to determine economizer damper position and AC compressor activation. This parameter change from airflow volume control to temperature-based control improves measurement precision while maintaining ventilation compliance and thermal comfort
Data Source
AI summary
A Fault Detection Diagnostic (FDD) correction method for increasing the cooling capacity delivered by an Air-Conditioning (AC) system with an economizer comprising: correcting/superseding at least one cooling fault/delay, the correcting/superseding selected from the group consisting of: correcting/superseding a High-limit-Shut-off-Temperature (HST) fault/delay based on detecting an Outdoor Air Temperature (OAT) is less than or equal to a High-limit-Control Temperature (HCT) during a thermostat call for cooling to enable economizer cooling otherwise delayed by the at least one HST fault/delay, superseding a thermostat second-stage time/temperature-deadband delay based on detecting an OAT is greater than or equal to an AC Control Temperature (ACT) during a call for cooling and energizing an AC compressor otherwise delayed by a thermostat second-stage time/temperature-deadband delay, superseding at least one economizer second-stage time/temperature delay based on detecting a thermostat second-stage cooling signal and energizing an AC compressor otherwise delayed by the at least one economizer second-stage time/temperature delay.