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Stop HVAC Communication Errors with Shielded Cable

If you've had HVAC techs chasing intermittent communication errors on a long control run, this one's for you. On extended thermostat and control wiring, especially outdoor runs, transient spikes from lightning storms are a common way to stop systems from talking to each other reliably.
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Using shielded cable on those runs eliminates a lot of these weird faults. If a rewire isn’t an option, bundle all unused conductors together and ground them on one side only (never both — that creates a ground loop and can make noise worse). Same rule applies to the shield itself: ground it on one side, not two.

Good, tight connections matter just as much — no double-lugging, no sketchy pigtails. Get these basics right up front and you’ll save yourself a callback down the road.

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