Adaptive Makeup Air System for Pressure Balance in Tight Enclosures
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Solution Overview
Problem
Existing makeup air systems in buildings fail to accurately compensate for air removed by exhaust systems, leading to pressure imbalances, drafts, and potential hazards like carbon monoxide accumulation, as they simply switch on and off without ensuring sufficient air infiltration.
Innovation Solution
A system comprising a damper, makeup air fan, sensor, and controller that measures exhaust fan characteristics to adjust the inflow rate of external air to match the outflow rate, ensuring balanced pressure and air quality through filtered and tempered air distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a forced makeup air system is used to compensate for high exhaust rates, then the pressure differential is reduced and air quality is improved, but the system complexity and energy consumption increase
Solution Approach 1:
The system incorporates a pressure sensor that continuously monitors the pressure differential across the building envelope and feeds this information back to a controller. The controller adjusts the makeup air fan speed dynamically to maintain pressure balance, eliminating the need for complex manual calibration and system design while ensuring reliable pressure compensation.
Solution Approach 2:
The makeup air fan operates with variable speed control rather than fixed speed, allowing the system to adapt dynamically to changing exhaust rates and pressure conditions. This dynamic operation simplifies the overall system design by replacing complex multi-fan configurations with a single adjustable fan that can match any exhaust scenario.
2Device complexity
If natural air infiltration is relied upon for makeup air, then the system simplicity is maintained, but the makeup air amount is insufficient and pressure differential exceeds acceptable levels
Solution Approach 1:
The system uses the building's existing exhaust fan as the trigger for makeup air delivery. When the exhaust fan operates, it automatically creates the pressure differential that the system detects and compensates for. This self-triggering mechanism eliminates the need for separate sensors and control logic while maintaining system simplicity and reliable pressure balance.
3Productivity
If existing forced makeup air systems are used, then makeup air is provided, but the systems do not accurately compensate for exhaust air and pressure imbalances persist
Solution Approach 1:
The pressure sensor provides real-time feedback on the actual pressure differential, allowing the controller to precisely adjust the makeup air fan output. This closed-loop control ensures accurate compensation that adapts to varying exhaust rates, unlike existing systems that deliver fixed airflow regardless of actual compensation needs.
Solution Approach 2:
The system dynamically changes the operational parameters (fan speed) of the makeup air fan based on measured pressure conditions. This allows precise matching of makeup air delivery to exhaust air removal rates, achieving accurate compensation that static systems cannot provide.
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
The system effectively compensates for air removal, preventing depressurization and hazards by dynamically adjusting airflow to match exhaust rates, improving indoor comfort and safety while managing air quality and pressure.
Implementation Method 1
a makeup air fan positioned in the air passage and configured to move the external air into the enclosure at an inflow rate
Implementation Method 2
a sensor configured to measure a quantifiable characteristic which can be correlated with or is otherwise indicative of the outflow rate
Implementation Method 3
a reasonable pressure differential between inside and outside is below three pascals (3 Pa), and it may not be possible to infiltrate an adequate amount of makeup air at a sufficient pressure to counter the outflow rate
Data Source
AI summary
A system and method for introducing external air into an enclosure having an exhaust fan for removing internal air at an outflow rate. A sensor measures a quantifiable characteristic which is indicative of the outflow rate. Based on the measured quantifiable characteristic, a controller determines a speed of a makeup air fan that results in the inflow rate matching the outflow rate, and opens a damper and runs the makeup air fan at the determined speed. For example, the sensor may measure an amount of electrical current flowing to the exhaust fan, and low and high speed exhaust fan values are stored in a memory, and corresponding low and high makeup air fan speeds are set. The controller then controls operation of the makeup air fan based on the amount of current flowing to the exhaust fan and the corresponding makeup air fan speed to match the inflow and outflow rates.