Ive noticed a few questions awhile ago about setback thermostats and pellet units. Harman just came out with a Technical Bulletin concerning them, and I thought Id take this time to communicate it before I forget all the particulars. All Harman pellet units can utilize a setback thermostat. The thermostat must be: 1. Millivolt compatible 2. Have gold contacts 3. be low voltage 4. be low current Harman reccommends the following Honeywell units for this use: RTH230B RTH6300B If there is a jumper between Rh and Rc, it must be removed from the terminal block of the thermostat. The thermostat must be connected in series with the room sensing probe using the Rh and W terminals of the thermostat. Except with the P38, which has no room sensing probe, the set-back thermostat MUST be used in conjunction with the room sensing probe. there are two modes of operation as well: Occupied Mode: (someones home) Set the thermostat to its max temp setting. The stove room-sensing probe will control room temperature, so set the desired room temp on the stoves temp dial. Unoccupied Mode: (noones home) Program the thermostat to the desired set-back temp. When the thermostat opens (is satisfied) the stove will go into a 4-blink status. If the stove is a auto-ignite model and the auto/manual switch is in auto, the stove will shut down. When the thermostat closes (calls for heat) the 4-blink status will reset and the stove will ignite. If the stove is a manual ignition model, or an auto-igniting unit with the selector switch set to manual, the stove will go into the 4-blink status when the thermostat opens (is satisfied) and the stove will go to a minimum burn and stay there until the thermostat closes (calls for heat). When the thermostat closes, the 4 blink status will reset automatically. Consult your owners' manual for a description of the 4-blink status. This error occurs when the contril board senses the room sensing probe isnt connected or has failed. This happens with the thermostat in series, since when the thermostat opens (is satisfied), there is a loss of continuity in the room-sensing circuit. The 4 blink status automatically resets when the board recognizes the room-sensing probe has been reconnected (ie: when the thermostat closes and calls for heat). Anyhow, here's the gist of the tech bulletin. If it sheds some light, great.