I haven't used a Powerline Network Adapter, but I have, many years ago, used the BSR X10 Home Appliance Remote Controls, which also transmitted signals over the AC powerline. (The BSR X10 sent low frequency ~100kHz to 300kHz signals, not the RF that the Powerline Network Adapters use, but it is the same concept.)
I had difficulty with "half" of my house, since I had 2 phase power circuitry (you might call it "double" circuit, since you seem to want to call single phase as "single circuit").
To get past the problem, to get the signal to cross-over from one phase to the other, and thus get control to work through the entire house, I placed a 0.1 micro-farad (I'm pretty sure, but it was quite a number of years ago) capacitor across the two "hot" phases. I did have to make sure that the voltage rating of the capacitor is AT LEAST 600 volts, and you do NOT want to use an electrolytic capacitor, since those are polarity dependant.
Since the Powerline Network Adapters work on a much higher frequency, then the capacitance value could be much lower and still work. That value is low enough that the 60~AC will not transverse the device, but the RF will.
By the way, I am NOT telling you to do this, it is only what I did to make my setup work. If you do it, and you cause any damage to yourself or to any property, then I do not take any responsibility.
Good luck in anything you do.