HVAC Fan and Blower Control with Independent Pressure Diagnostics
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Solution Overview
Problem
Current HVAC systems face challenges in efficiently operating across a wide range of outdoor temperatures due to hardware interlocks that prevent direct control of condenser fans based on both refrigerant pressure and outside air temperature, leading to potential energy wastage and compressor damage from faulty pressure sensors.
Innovation Solution
An HVAC controller with separate data paths for refrigerant pressure sensors and compressor stages, allowing independent control of compressor stages and condenser fans irrespective of sensor states, and generating error messages for faulty sensors to maintain system operation and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refrigerant pressure sensors are coupled through hardware interlocks to control condenser fans, then system safety is improved by preventing compressor damage, but system flexibility deteriorates due to inability to operate across wide temperature ranges
Solution Approach 1:
The patent segments the control system by providing separate data paths for each pressure sensor (first and second pressure sensors) to the controller, allowing independent evaluation of each sensor's signal. This enables the system to bypass faulty sensors while maintaining protection through functional redundancy, thus preserving reliability while improving adaptability across different operating conditions.
2Reliability
If parallel sensor coupling is used to control condenser fans, then measurement redundancy is improved, but diagnostic capability deteriorates due to inability to identify faulty sensors
Solution Approach 1:
The controller is configured to separately receive and evaluate signals from the first and second pressure sensors through distinct data paths. This segmentation enables the system to independently assess each sensor's output, identify which sensor is providing faulty readings, and generate specific diagnostic information about sensor status while maintaining redundant protection coverage.
Solution Approach 2:
The system implements feedback mechanisms where the controller continuously monitors pressure sensor signals and compares them against expected operating ranges. When sensor readings indicate abnormal conditions or conflicts between sensors, the controller generates diagnostic feedback to identify the faulty sensor and adjusts fan control accordingly, maintaining system reliability while providing clear fault detection.
3Reliability
If condenser fan operation is strictly controlled by pressure sensor signals, then compressor protection is improved, but energy efficiency deteriorates due to inability to optimize for temperature conditions
Solution Approach 1:
The patent implements dynamic control where the controller adjusts condenser fan operation based on real-time evaluation of pressure sensor signals and operating conditions. The system can vary fan speed and operation timing to optimize energy consumption while maintaining compressor protection through coordinated control of multiple fans and stages, rather than relying on static pressure-switch control.
Solution Approach 2:
The system changes operational parameters by controlling different stages and varying fan speeds based on actual system needs rather than binary on/off control. This allows optimization of energy consumption by matching fan output to actual cooling requirements while maintaining pressure protection through coordinated multi-stage operation.
Data Source
AI summary
An HVAC controller, a method of operating an HVAC controller and an HVAC system employing the controller or the method. In one embodiment, the HVAC controller includes: (1) a processor couplable to at least two refrigerant pressure sensors via separate data paths to receive input signals therefrom and further couplable to a compressor stage and a condenser fan to provide output signals thereto and (2) memory coupled to the processor and configured to store a software program capable of causing the processor to command the compressor stage and the condenser fan to turn on irrespective of a state of an input signal generated by either of the at least two refrigerant pressure sensors and generate alternative error messages at least partially depending upon whether or not a high pressure shutdown occurs after the processor commands the compressor stage and the fan to turn on.