We recently installed a Rheem RPRL036Jez Heat Pump (2 stage) (abbreviated as HP for later discussion), RPRLHM3621JA Air Handler (AH) with a 5KW auxiliary electric heat strip, and Rheem's TST304UNMS Thermostat (Th), and the wiring is a bit of an issue. The contractor and the tech suport at the distributor and I all have different opinions as to the wiring of the W2 terminal on the Thermostat and the Air Handler.
The spec sheet shows (Th)WE connected to (AH)W1 and (HP)D, these being the Emergency Heat connections, and the HP defrost cycle; then (Th)W2 is to be connected to (AH)W2, for third stage auxiliary heat (the heat strip). The contractor installed an 8-wire harness, connected B/B, Y/Y1, Y2/Y2, G/G, RH+RC/R, C/C, WE/W1 and connected the 8th wire to the (Th)L terminal for the Heat Pump malfunction indicator, leaving no wire available for (Th)W2; he then jumpered (Th)WE to (Th)W2, left (AH)W2 disconnected, claiming (AH)W2 served no purpose. Operationally, the thermostat works fine in AC mode; when calling for heat, Stage 1 works (solid lit indicator); upping the temp on the Thermostat 3 degrees energizes Stage 2 and the “+2”indicator blinks, but the Thermostat gives an error message "call for service"; I'm not even sure if Stage 3 ever engages.
One tech support person at the distributor feels W2 should be separately connected as per the spec sheet for the equipment, another agrees with the contractor that W2 is unnecessary, and Rheem won't let me talk to a factory rep at all. Another forum response indicated that if (Th)W2/(AH)W2 are not wired together, then if (Th)WE/(Th)W2 are jumpered at TH, then (AH)W2/(AH)W1 should also be connected together at the Air Handler terminal.