Economizer having damper modulation
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Solution Overview
Problem
HVAC systems with incorrectly placed mixed air temperature sensors reduce energy savings by incorrectly modulating outside air damper, leading to inefficient use of free cooling energy due to the sensor measuring lower temperatures after cooling coil engagement.
Innovation Solution
Implementing a control function in the economizer to use outside air temperature values when the mixed air temperature sensor is incorrectly placed, ensuring the damper remains open even when the cooling coil is activated, thereby maximizing energy savings by comparing outside air and mixed air temperatures and prioritizing outside air temperature for control when it is good for economizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the mixed air temperature sensor is installed in the discharge air area downstream from the cooling coil, then the sensor can be easily installed and connected to the economizer, but the sensor measures lower temperatures after cooling coil engagement causing incorrect damper modulation and reduced energy savings
Solution Approach 1:
The patent inverts the conventional approach by using the outside air temperature sensor reading instead of the mixed air temperature sensor reading when the mixed air sensor is incorrectly placed downstream from the cooling coil. This inversion allows the system to override the erroneous low temperature measurements and maintain proper economizer operation, preventing unnecessary closure of the outside air damper and preserving free cooling energy savings
Solution Approach 2:
The patent introduces an intermediary control mechanism that detects when the mixed air temperature sensor is incorrectly placed (downstream from the cooling coil) and substitutes the outside air temperature sensor reading as a mediator to provide accurate temperature information for damper control decisions, thereby resolving the measurement error without requiring physical relocation of the sensor
2Ease of operation
If the economizer closes the outside air damper based on incorrect low temperature readings from the misplaced sensor, then the system responds to the sensed temperature, but free cooling energy is unnecessarily reduced and mechanical cooling is engaged prematurely
Solution Approach 1:
The patent implements a feedback mechanism where the economizer continuously monitors the temperature reading from the mixed air temperature sensor and compares it with the outside air temperature sensor reading. When the mixed air sensor reading is lower than the outside air temperature (indicating incorrect placement downstream from the cooling coil), the system provides feedback to override the erroneous signal and maintains the outside air damper in the open position, preventing premature engagement of mechanical cooling and reducing energy consumption
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
This approach ensures that the outside air damper remains open when outside air is suitable for economizing, maximizing energy savings by preventing unnecessary cycling and ensuring continuous use of free cooling energy.
Implementation Method 1
A cooling mechanism may be at the output of the discharge air
Implementation Method 2
A temperature sensor may be positioned at the input for outside air and at the output of discharge air
Data Source
AI summary
A system having a mixed air box with inputs of return air from a space or spaces of a building, and of outside air. The mixed air box may have an output of discharge air to the space or spaces of the building. The air from the output may be return air that is conditioned with cooling, heat, or outside air. A damper may be situated at the input of outside air to the mixed air box. A temperature sensor may be positioned at the input for outside air and at the output of discharge air. A cooling mechanism may be at the output of the discharge air. The temperature sensor may be downstream from the cooling mechanism. An economizer may have connections with the damper, the temperature sensor and the cooling mechanism.