Bryant Evolution Furnace Communication Rewire | Simplifying ABCD Bus for Reliable Operation

In this video, I re-establish the communication wiring on a Bryant Evolution two-stage communicating gas furnace after diagnosing inconsistent system operation linked to the original wiring setup.

The previous installation had two leads fastened under each terminal screw — for example, the A terminal had both the outdoor unit lead and the control lead secured together under the same screw. While this configuration can function, I’ve seen it cause intermittent communication issues and inconsistent performance over time due to poor contact pressure and unreliable signal continuity.

After running the query through both ChatGPT and Google’s Gemini, I confirmed the industry consensus that the best practice is one lead per terminal to ensure a secure, dedicated transfer of the communicating DC voltage between the indoor unit, outdoor unit, and control.

To implement this properly, I reconfigured the system using WAGO lever nut connectors as follows:
• Two 3-port connectors for the A and B terminals (used by both indoor and outdoor units).
• Two 2-port connectors for the C and D terminals (used exclusively by the indoor unit).

This revised layout provides several key advantages:
✅ Improved reliability through secure and independent terminal connections.
✅ Simplified troubleshooting—future technicians can easily isolate circuits or verify voltage from the outdoor unit by simply disconnecting the A & B terminals.
✅ Cleaner wiring design that makes system communication pathways immediately understandable and expandable.

By eliminating the dual-lead-per-terminal configuration, this approach promotes consistent performance, easier diagnostics, and long-term dependability for any communicating system setup.

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