Identifying and Troubleshooting Powerline Noise and Control Problems

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How can I make my X10 lighting control more reliable? Why can I not control lights sometimes?


X10 signals can be adversely affected by electrical "line noise" on your house wiring. Common sources of line noise are electric motors; fluorescent, halogen, and sodium vapour lights; TV sets; computers (including laptops); DC power adapters; and Uninterruptable Power Supplies.

Some sources of electrical noise interference can be periodic as well; for example, the motor in your refrigerator will cycle on and off at random times to maintain a constant temperature. It generally only introduces noise into the powerline when it is running.

X10 Power Line Commands (the commands that X10 controllers send over your house wiring) will work reliably with some line noise. However, the effect of multiple sources of noise altogether can make control less reliable.

How to troubleshoot unreliable Power Line Control

Confirm your modules work

The first step is to confirm that all of your modules work correctly. An easy way to do this is to isolate them on a surge protector/suppressor. The outlets on most surge suppressors are generally all wired together, so X10 signals easily pass from one outlet to the other. Incoming power is filtered, so noise from other wall outlets will generally be reduced (attenuated). This lets you create a clean environment to test your modules individually.

In order to perform this test, you will need a surge protector with enough room between outlets that you can plug a transceiver module (TM751 or RR501) and several lamp or appliance modules into it. You will also need a Radio Frequency (RF) controller (like an HR12A Palm Pad remote control) set to the same codes as your transceiver and modules. Instead of a transceiver, you could also use an ActiveHome Professional interface. With your transceiver and the modules you are testing plugged into the surge strip, all set to the same house code, and lamps plugged into each lamp module, you should be able to turn on and off your lights. This test should be 100 percent reliable. If you have modules that are not reliable when plugged into the surge strip, you may want to replace them (or try different lamps; also make sure a lamp is in its On position before plugging it into a module). If none of the modules work, then try another surge protector or replace your transceiver.

Locate any source of noise

Once you have confirmed that your transceiver and modules all work correctly, the next step is to try to locate the source of noise and isolate it. Professional installers trying to troubleshoot PLC noise problems should use a troubleshooting kit utilizing an XPTT (test transmitter) and XPTR (test receiver) pair to get a signal strength reading for each outlet. XPTT and XPTRs are available from X10 Pro ( These kits would be also be a great investment for a homeowner with a whole home automation system. You plug the XPTT into the outlet where your ActiveHome Pro interface plugs in; then try plugging the XPTR into each outlet to get a reading of the strength of the X10 signal. Then follow the steps below for any outlet showing reduced signal (less than 2 Volts).

A lamp module, and a small lamp such as a child's night-light can be used to help track down the source of noise on circuits. Turn off as many appliances and lights (especially florescent and Halogen) as possible. Then plug your lamp module and light into each outlet in the home, and verify that you are able to turn the light on, turn the light off, and brighten and dim the light with your remote. Note any outlets that do not work, or do not respond consistently.

Remember, the radio frequency range of your remote is at most 100 feet, so you may need to walk closer to your transceiver module to use it; then walk back to the light to check if it is responding. If the outlets all work correctly, then try turning your lights and appliances back on, and re-test them. If they continue to work, you may need to test again later and try to determine when they do not work (when your refrigerator, hot-water heater, or central-air system cycle on, for example).

If you are having problems with some outlets, try unplugging everything from that specific circuit. Remember, several outlets will generally share the same circuit (you may be able to find more information in your breaker box). Make sure that you unplug any surge protector or outlet strips, as some models may filter X10 signals even if nothing is connected to them. If you still cannot reliably control lights on a specific circuit, you may have a phase issue. Phase couplers (both active and passive) are available from X10 Pro ( Depending on the model you choose, you may require the services of an electrician to install one.

Additional suggestions

If possible while testing, unplug all appliances in your home. If this seems to improve reliability, you can purchase line filters from X10 Pro (, and use them on the appliances to help block any line noise they are generating. X10 house wiring signals can travel from a neighbor's house to yours, so if you believe that you are being affected by a neighbors X10 system, try the following:

  • From the Tools Menu of ActiveHome Professional, select "Find Other Computers." If you see house codes with Red blocks, this means that someone nearby may be using that house code. You can change your house codes to avoid any that a neighbor uses. This ActiveHome Pro feature shows the results after the last time the log file was cleared. If you make changes, clear the log file, and check it again after a few days.

It is also possible to purchase a filter for your house wiring to block incoming X10 signals from a neighbor's house from X10 Pro (; this generally requires installation from a professional electrician.

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