Noise on 3-way Traveler Wires

Question

My WS13A and a WS14A are setup for a 3-way application with fluorescent lights. My WS14A will only turn the light off. Why?

Answer

You should have both ON and OFF control from both switches. It sounds like there is noise on the house wiring. Devices such as baby monitors, wireless intercom systems, or anything that transmits signals over the house wiring might interfere with X10 codes. Televisions and computers can also sometimes transmit noise, even if they are turned off. This interference will commonly stop X10 signals from getting through to the correct module(s), causing intermittent control.

When the light is ON, the load the switch puts across the house wiring reduces interference (so you can then turn the light OFF from the WS14A companion switch). Then once the light is off, and the load is removed, the noise comes back, you cannot turn the light ON from the companion switch.

If the issue is consistent (not intermittent), the noise interference may be on the traveler wires and NOT produced by the load being controlled (coming from another device). The problem is more likely a very long wire run between the two switches.

It can be tricky and costly to track down and eliminate noise on traveler wires. Often, using a [SS13A http://www.x10.com/automation/ss13a_s.html] or an [XPT1 http://www.x10.com/pro/automation/xpt1w.htm] is the most sensible control solution.