When I installed my XTB-IIR, I added a new double-breaker in my breaker box (one half connects to each phase), and brought that out to feed a new NEMA 6-20 (if I remember correctly) 220V outlet, mounted in a separate box right near my breaker box. I attached a length of 12/3 (although 14/3 would have been a bit easier to work with) to the terminals on the board inside the XTB-IIR, and connected the other end to a NEMA 6-20 right-angle plug (I got both the plug and outlet at Home Depot). I didn't need the right-angle plug, but it makes the installation look a lot neater.
At the same time, I wired an additional split-wired duplex outlet in the box with the 220V socket.
The top outlet is wired to one "hot" wire from the new breaker, and the bottom outlet is wired to the other "hot" wire.
It was only a few minutes of extra work to add this when I was putting the new box in. The two outlets can function as "test" outlets to locate noise or other problems, which can be measured separately on each phase. Because there is nothing else on those circuits (other than the XTB-IIR and the CM15A plugged into it), I can turn off everything else in the house to isolate potential noise issues.