Dual-Processor Furnace Control Board for Update-Safe HVAC Control
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Solution Overview
Problem
HVAC furnace controllers often lose safety certifications when software updates are applied, leading manufacturers to avoid issuing updates due to the time-consuming and costly recertification process.
Innovation Solution
Implementing a dual controller architecture with a primary application processor for non-safety-critical functions and a safety processor for safety-critical functions, allowing software updates to be applied to the primary processor without affecting safety certifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If software updates are applied to the furnace controller, then system functionality is improved, but safety certifications are lost
Solution Approach 1:
The controller is divided into two separate processors: an application processor for non-safety-critical functions and a safety processor for safety-critical functions. This segmentation allows independent updates to the application processor without affecting the safety processor's certification status.
Solution Approach 2:
Safety-critical functions are extracted from the main application processor and placed in a dedicated safety processor. This extraction isolates the safety functions from software updates, preserving certification while allowing updates to the application processor.
2Reliability
If recertification is performed after software updates, then safety certifications are maintained, but time and cost increase
Solution Approach 1:
The safety processor is pre-configured with certified safety functions before the product is released. This preliminary configuration ensures that safety certifications are already in place and will not require recertification when application processor software is updated.
Solution Approach 2:
By segmenting the controller into application and safety processors, recertification becomes unnecessary for routine software updates since the safety processor remains unchanged and retains its certification.
3Device complexity
If a single processor is used for all functions, then device complexity is reduced, but software updates affect safety functions
Solution Approach 1:
The controller architecture is segmented into two processors with distinct responsibilities. The application processor handles non-safety functions while the safety processor handles safety-critical functions, ensuring independence and allowing updates without compromising safety.
Solution Approach 2:
Different parts of the controller have different qualities and functions. The application processor is optimized for general-purpose updates and functionality, while the safety processor is optimized for certified safety functions, allowing each to be updated or modified independently based on its specific requirements.
Data Source
AI summary
A system and method are disclosed that provide for a dual processor architecture in a furnace or HVAC controller. One processor can control non-safety-critical components and is operable to receive software updates. The other processor can control safety-critical components and is not capable of being updated. Safety-critical components can comprise a flame sensor, gas valve and an igniter.