I'm trying to have two different X-10 devices provide power to a domestic hot water recirculating pump, but at different points in the logiical daisy chain. If two X10 devices are wired to provide power to the pump -- one ("A") through a timer and the other ("B") bypassing the timer, there's a chance that B could be backfeeding AC to the output of A while A is in the OFF state. Can X-10 devices tolerate this kind of backfeed, or must I isolate them with a relay?