Multi-Zone HVAC Staging Control for Delayed Capacity Switching
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Solution Overview
Problem
HVAC systems with zone control and multiple stage fluid temperature conditioning devices face challenges in determining the proper control strategy, leading to inefficient operation, excessive cycling, and temperature deviations due to inadequate timing and staging mechanisms.
Innovation Solution
A controller with multiple thermostat terminals, flow control terminals, and timers that initiate timing counts for each zone, determining when to up-stage the conditioning device based on individual zone demands and a programmed delay parameter, while incorporating a time buffer to prevent frequent staging changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single thermostat controls the HVAC equipment, then the system is simple to operate, but the heating and cooling loads of individual areas cannot be satisfied and temperature deviations occur
Solution Approach 1:
The patent divides the building into multiple zones, each with its own thermostat, allowing independent temperature control for different areas. This segmentation resolves the contradiction by maintaining simple operation within each zone while achieving accurate temperature control across the entire building through distributed control.
Solution Approach 2:
The patent transitions from a single-point control (one thermostat) to a multi-point control system by adding spatial dimensionality. Multiple thermostats are positioned at different locations throughout the building, enabling temperature control in three-dimensional space rather than at a single location, thus resolving the temperature deviation issue while maintaining operational simplicity.
2Reliability
If multiple thermostats are positioned at different zones, then temperature control accuracy improves, but the system complexity increases
Solution Approach 1:
The patent merges the control functions of multiple zones into a single centralized HVAC equipment unit. Instead of having separate equipment for each zone, the conditioned fluid is distributed through a common system with flow control devices that regulate delivery to different zones, simplifying the overall system while maintaining multi-zone temperature control accuracy.
Solution Approach 2:
The single HVAC equipment unit is designed to serve multiple zones simultaneously, making it a universal system that can condition air or fluid for different areas. This multi-functionality reduces device complexity by eliminating the need for separate heating and cooling equipment in each zone while maintaining accurate temperature control through the controller's ability to manage multiple thermostats.
3Power
If the conditioning device operates at higher output stages, then the heating or cooling capacity increases, but energy efficiency decreases and equipment wear increases
Solution Approach 1:
The patent implements dynamic staging control that adjusts the output stage of the conditioning device based on real-time zone demands. The controller monitors thermostat signals and timing counts to determine when to transition between stages, enabling the system to provide high capacity when needed while operating at lower, more efficient stages during mild conditions, thus resolving the contradiction between power and energy efficiency.
Solution Approach 2:
The patent changes the operational parameters of the conditioning device by introducing multiple output stages with different capacity levels. The system can switch between first and second stages based on the intensity and duration of thermostat calls, allowing optimal matching of capacity to demand and preventing excessive energy consumption and equipment wear from continuous high-stage operation.
4Speed
If the conditioning device responds quickly to thermostat calls, then temperature control responsiveness improves, but excessive cycling occurs and equipment lifespan decreases
Solution Approach 1:
The patent implements preliminary timing action by requiring a minimum timing count before the conditioning device responds to thermostat calls. This delay prevents immediate response to transient temperature fluctuations, reducing excessive cycling and extending equipment lifespan while still providing timely response to sustained heating or cooling demands through the staged operation mechanism.
Solution Approach 2:
The patent introduces periodic timing intervals before the conditioning device activates in response to thermostat calls. This periodic action filters out short-term temperature variations and ensures that the system responds only to sustained demands, reducing cycling frequency and equipment wear while maintaining adequate response speed for genuine temperature control needs.
Data Source
AI summary
A controller for an HVAC system having a plurality of zones and having a multiple stage fluid temperature conditioning device. The controller is configured to receive a plurality of thermostat signals and to transmit a signal to control one of a plurality of flow control devices in response to a call for conditioning in one of the plurality of zones. The controller also includes one or more timers that are connected to the thermostat terminals, where the one or more timers are configured to initiate a separate timing count upon each call for conditioning in any one of the plurality of zones. In addition, the controller includes one or more staging terminals for transmitting staging signals to control a multiple stage fluid temperature conditioning device, where the transmission of the staging signals determines whether the conditioning device will operate at a relatively higher output stage. The controller is also configured to make a timing count determination to determine if any one of the separate timing counts initiated upon each call for conditioning in any one of the plurality of zones exceeds a timing delay parameter. The transmission of staging signals depends on the timing count determination. A method is also disclosed.