To add X10 control, plug the X10 module into the wall outlet and the GFCI Plug-in Outlet into the socket on the Appliance module. I know, it s hard to believe that something would not like X10 signals. We sometimes get calls and letters from customers who mention control problems on GFCI protected circuits. Typically, X10 devices that are down-stream of some GFCI devices will not react to X10 signals. We have concluded that some GFCI fixtures are attenuating the X10 signals.
Some brands have more of a negative effect on the signals than do others.
Find a GFCI outlet that does not attenuate signals. Buy your GFCI devices from a supplier that has a liberal return policy. If the brand you install does not pass X10 signals, exchange it for a different brand. Moving to a different model within the same manufacture s family may not fix the problem. Even after the GFCI outlet, there will be plenty of signal strength at the outlet.