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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Evolution 95 S furnace as installed and connected

Customer Question

I have a Bryant Evolution 95 S furnace as installed and connected to natural gas in May, 2008. Everything worked fine until Nov. 2015. At that time the furnace shut down and the fancy thermostat control recorded a message of "failure to communicate". Turning the main switch off and back on at the furnace restored it's brain and it worked fine until Mar. 5th, 2016. Again a shut-down and the same message. Then on MAR.11th, the communication error again. I've been told that Bryant has advised replacing the wire from the Thermostat/Computer to the furnace with a new four wire conductor that has better insolation qualities and the problem will go away. Since this suggests a design error/problem by Bryant, is the factory offering any help/compensation in providing wire and instruction to authorized dealers. Dealer Service calls are expensive and I wish to understand what is going on. Thank you ***** E-mail;***@******.***.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, the situation with the wire is that both shielded, and unshielded cable can be used. Unshielded does not resist electrical interference from outside sources as well as shielded. You most likely have unshielded cable.

You can inspect the cable and if there is no foil wrap around the wires inside the cable jacket, then it is unshielded.

I have seen extreme cases where unshielded cable, such as you have, works well .... but sometimes there are electromagnetic influences on the communication cable that will produce the communication error you are reporting.

Since however your system has been working well since 2008 it is not likely replacing your communication cable with shielded cable will solve the problem. But it might (10% chance)

There is most likely a problem with the thermostat or the printed circuit board inside your air handler that is at fault. Its a tricky diagnosis.

Tell me a lot about your skill sets so that I can coach you most effectively.

We can go from there.

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