Voltage drop on a 40 foot run caught me off guard last Friday

I was putting in a new wireless panel at a warehouse in Tulsa and the keypad kept losing signal to the main board. Turns out the data wire had to go 40 feet past a bunch of motor starters, and even though the cable spec said it was fine, the noise caused dropouts every few minutes. I ended up rerouting it along a different wall and adding a ferrite bead near the panel, which fixed it. Anyone else run into interference from industrial equipment that should be too far away?

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riverknight6d ago

Ferrite bead was a smart move, those things save my tail more than I like to admit. Motor starters are nasty, they throw all kinds of harmonics back down the line even when the math says you're clear of them. Ran a similar headache at a bottling plant a few years back, conveyor VFDs were killing a temp sensor signal that was supposedly 30 feet away with plenty of margin. What got me was the cable tray itself, it was sharing space with the power feeds, and the magnetic field from those big conductors did more damage than the actual distance. Ended up pulling the data line in its own steel conduit, not even grounded fancy, just plain EMT, and that killed the noise completely. Your reroute probably got you out of the worst of the field, but if it ever starts acting up again look at separating the data path from any high current runs on the way back to the panel.

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