Makes me wonder whether you could pick off the 120kHz signal at the cm15a outlet point with a capacitive high pass filter, maybe even a series resonant LC circuit, then use coax to run that over to the breaker panel and reinsert it there using a similar series circuit. At the breaker panel, you could use a dedicated breaker.... or have two of the little series circuits and feed each of two breakers to catch both legs. (not entirely legal -- so mount a dedicated 110 (220?) vac outlet right at the breaker panel and connect the LC circuit to the AC line there?)
Don't know what the loss of 120 kHz would be in coax, but it would certainly be much less than using electrical wire. Much cheaper too.
I suppose there could be a problem with the original cm15a signal being out of phase with the signal carried on the coax. But it would seem the coax carried one would be quite a bit higher than the cm15a signal (capture ratio helps). Or you might just get inside the cm15a and reroute the signal away from the AC plug to a small jack on the module and just bypass the CM15a to breaker panel AC path all-together.
You would, most likely, want to be careful not to electrocute yourself or an acquaintance.
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