Crestron HZA-CONV-THSTAT-2WIRE Common Wire Adapter

Older thermostat runs frequently arrive at the wall with two conductors and no common wire, which is the usual reason a networked thermostat cannot be dropped into a retrofit. The HZA-CONV-THSTAT-2WIRE adapter solves that at the HVAC end: it lets the Horizon HZ-THSTAT wireless thermostat power itself and make an HVAC call over as few as two wires, without borrowing current from the call relay connections the way a power-stealing thermostat does.

The adapter is a small Noryl plastic housing with three terminals to the thermostat side and three to the HVAC side, carrying reference, common, and a combined heat and compressor relay rated 1 A at 24 VAC. It surface mounts with the two included screws. Where a common wire is already present, the same adapter can be used to free up an extra conductor for a system upgrade. The HZ-THSTAT itself is ordered separately.