Smart Thermostat Circuit Isolation for HVAC Wiring Faults
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Solution Overview
Problem
Incorrect wiring connections during HVAC system installation or upgrades can lead to short circuits, causing permanent damage to thermostats and other components, which is particularly problematic for user-installable thermostats where non-expert installers may incorrectly connect wires and struggle to diagnose and correct errors.
Innovation Solution
A thermostat with solid-state switching elements and power monitoring circuitry that detects anomalies in voltage and current, automatically isolating the system during anomalies and providing error indications to assist users in correcting wiring issues, while also preventing damage through automatic shut-off and restart mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fuse-based protection is used, then protection against short circuits is provided, but customer satisfaction deteriorates due to blown fuses requiring service calls
Solution Approach 1:
The patent replaces the mechanical fuse-based protection system with an electronic solid-state switching element (MOSFET) controlled by a microprocessor. This substitution eliminates the need for physical fuses that blow and require replacement, while providing continuous electronic monitoring and protection against short circuits through automated detection and isolation of wiring errors.
2Ease of operation
If user-installable thermostats are provided, then ease of installation is improved, but risk of incorrect wiring increases
Solution Approach 1:
The patent implements automated feedback mechanisms where the microprocessor continuously monitors voltage and current characteristics to detect wiring errors. When incorrect wiring is detected, the system provides real-time feedback by identifying the specific erroneous connection and guiding the user through correction steps, thereby maintaining ease of installation while mitigating the risks of incorrect wiring.
Solution Approach 2:
The thermostat performs self-diagnosis and self-correction of wiring errors through automated detection and isolation mechanisms. The system automatically identifies short circuits and isolation faults, and can autonomously isolate problematic connections without requiring user intervention or service calls, thus enabling user-installable thermostats to operate safely despite potential wiring mistakes.
3Ease of operation
If solid-state switching elements are used instead of fuses, then customer satisfaction is improved by eliminating blown fuses, but device complexity increases
Solution Approach 1:
The microprocessor-based control system performs multiple functions: it monitors voltage and current characteristics, detects various types of wiring errors, controls the solid-state switching elements, provides user guidance, and manages system protection. This multi-functional approach consolidates what would otherwise require separate dedicated circuits into a single intelligent controller, thereby managing device complexity while providing comprehensive protection and user-friendly operation.
Data Source
AI summary
A smart-home device may include wire connectors that couple to an inductive power coil and a load, one or more solid-state switching elements having a first operating state in which they create a connection between the wire connectors and a second operating state in which the connection is interrupted. The smart-home device may cause the switching element(s) to operate in the first operating state to power the load; detect an anomaly from measurements from power monitoring circuitry; cause the switching element(s) to operate in the second operating state for at least a first time interval; and after the expiration of the first time interval, cause the one or more switching elements to operate in the first operating state and determine whether the anomaly is still present.