Metal parts are the only ones that often need to be grounded, and the only metal part not enclosed inside the TS4 device is the the TS4-R mounting bracket. The device inside the plastic enclosure is floating and therefore does not require grounding. The electronics work relative to the PV module (not relative to ground), and the metal mounting bracket is completely separated from the electronics inside.
The TS4 and TS4-R units can be tested for leakage just like standard PV modules do.
The TS4 and TS4-R units can work with inverters and modules regardless of their grounding method: positive, negative and/or bipolar inverters.