Douglas Krantz - Technical Writer - Describing How It Works

Can I Mix High and Low Voltage Wiring?

The code shows some installation practices that need to be followed. However, cross talk, where AC power on one set of wires is magnetically transferred to the other wires, is a problem. The codes and rules are mostly about safety, the crosstalk isn't about safety, it's about signal interference.

Can I Mix High and Low Voltage Wiring?

Mr. Krantz

Question. Can phone lines, fire alarm cables, and 120-240 cables be put together in an outdoor back box?

Signed E

Besides the legal aspects which are fire and safety issues, there's the interference problem.

The voltages and currents from the 120-240 volt cables will be cross-talking to the low voltage cables. How much cross talk is produced will be affected by the actual currents in the high voltage cable, how tight they are to the low voltage cables, and the distance they are running together. The tolerance to this interference is a great issue, and depends on the signals used in the low voltage cable.

Unless you are prepared for major problems from all these issues down the road, I wouldn't recommend it under any circumstances.

Douglas Krantz
Life Safety
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