HVAC Fan Control Using Variable and Constant-Speed Exhaust Fans
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Solution Overview
Problem
Existing HVAC systems are inefficient and resource-intensive due to the use of multiple motor drives or a single fan motor to control airflow, which increases implementation costs and physical footprint.
Innovation Solution
An HVAC unit with a combination of a variable speed fan and a constant speed fan, controlled by a controller that determines target airflow and activates the fans accordingly, using a single motor drive to reduce power requirements and component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple motor drives or a single fan motor are used to control airflow, then airflow control capability is improved, but implementation cost and physical footprint increase
Solution Approach 1:
The system divides the airflow control function into two segments: a variable speed fan for continuous airflow adjustment and a constant speed fan for fixed airflow provision. This segmentation allows the system to achieve versatile airflow control while using simpler, more cost-effective motor drive configurations.
Solution Approach 2:
The controller universally manages both variable speed and constant speed fans through a single control system, enabling the HVAC unit to adapt to different airflow requirements using a unified control architecture that reduces overall system complexity.
2Measurement precision
If multiple motor drives are used to control airflow, then airflow control precision is improved, but power requirements and component count increase
Solution Approach 1:
The airflow control function is segmented between variable speed and constant speed fans, allowing precise airflow control to be achieved through the variable speed fan while the constant speed fan provides reliable baseline airflow, reducing the need for multiple complex motor drives.
Solution Approach 2:
The system uses a constant speed fan to provide a baseline airflow that may be excessive for some conditions, allowing the variable speed fan to operate at lower power levels to fine-tune airflow precision, thereby reducing overall component requirements.
Data Source
AI summary
The present disclosure relates to a heating, ventilating, and air conditioning (HVAC) unit configured to supply conditioned air to a conditioned space. The HVAC unit includes a first exhaust fan capable of operating at variable speeds and a second constant-speed fan. The HVAC unit also includes a controller configured to determine a target airflow to be provided to the conditioned space, cause actuation of the first exhaust fan at a variable fan speed when the target airflow is greater than zero, and cause actuation of the second exhaust fan when the target airflow is greater than an airflow threshold.