Overview Chronotherm IV Plus RF Wireless Programmable Thermostat provides wireless control of 24 Vac heating and cooling systems. Use with W8665A for single-zone applications or W8665E for zoning applications. Features No wires to thermostat allows easy installation. Ideal for retrofit zoning. Use when current thermostat inconveniently located or to add a thermostat to a room addition. Easy-to-read large display with bright back-lighting. Full seven-day flexible program capability; different schedules and temperature setpoints selectable each day. Copy key makes programming easier and faster. Daylight Savings Time (DST) key. Models available with programmable fan operation. Easy temporary temperature setpoint changes for current period, vacation hold (1 to 255 days) or indefinite hold. Frequently used keys are conveniently located near LCD. Configurable features allows one model to replace many different models. -F or C temperature display. -Automatic or manual changeover. -Electric or conventional heat fan operation. -Adjustable heating cycle rate. Minimum-off time for cooling compressors and heat pumps protects equipment. Easy installation, setup and system test. System test simplifies troubleshooting and saves time by overriding time delays. Adaptive Intelligent Recovery control brings room temperature to temperature setpoint at programmed time. Setpoints are permanently held in memory (no batteries used) and retained during power outages. Adjustable temperature range stops. Product Specifications ApplicationConventional systems Dimensions (in.)3 3/4 in. high x 6 1/16 in. long x 1 9/16 in. deep Dimensions (mm)95.3 mm high x 154 mm long x 39.7 mm deep CommentsEach thermostat is encoded with unique serial numbers.; Required accessory (not included): W8665A or W8665E Receiver Module MountingHorizontal Frequency50 Hz; 60 Hz StagesSee W8665 Tradeline ValueTradeline Operating Humidity Range (% RH)5 to 90% RH, non-condensing Supply Voltage18 to 30 Vac Switch Positions (System)HEAT-OFF-COOL-AUTO Switch Positions (Fan)AUTO-ON Sensor ElementThermistor Differential Temperature (F)± 1 F Differential Temperature (C)±0.5 C ColorPremier White Ambient Temperature Range (F)40 F to 110 F Ambient Temperature Range (C)4 C to 43 C Programmability7 Day Program Power MethodBattery Terminal DesignationsWireless ChangeoverAuto/Manual Selectable Setting Temperature Range (F)Heat: 40 F to 90 F; Cool: 45 F to 99 F Setting Temperature Range (C)Heat: 4.5 C to 32 C; Cool: 7 C to 37 C Cool Current1.5A running, 7.5A inrush Heat Current1.5A running, 3.5A inrush Fan Current0.5A running, 2.5A inrush Transmitter Range3 ft. minimum; 200 ft. maximum. Transmitter Frequency345 MHz