70803-IM 12/18/06 2:10 PM Page 1 ® Model 70803 INSTALLATION AND OPERATING INSTRUCTIONS Non-Programmable Electronic Thermostat Heat/Cool
70803-IM 12/18/06 2:10 PM Page 2 Compatible with low voltage single stage gas, oil or electric heating or cooling systems and single stage heat pumps. For use on 24VAC systems (not to exceed 30VAC) and 250mv to 750mv millivolt heating only systems. WARNING! • To prevent electrical shock and/or equipment damage, disconnect electric power to system at main fuse or circuit breaker box until installation is complete. • This thermostat requires 2 AA Alkaline batteries for power.
70803-IM 12/18/06 2:10 PM Page 3 Removing The Existing Thermostat 1) CAUTION: Make certain the power to the system has been disconnected. 2) Remove the cover of the old thermostat and locate the wires that are connected to the terminal board. IMPORTANT: Before removing these wires, NOTE (ON A PIECE OF PAPER) THE COLOR OF EACH WIRE AND THE CORRESPONDING TERMINAL MARKING ON THE OLD THERMOSTAT. 3) Remove the wires from the terminals. Remove the old thermostat and mounting base from the wall.
70803-IM 12/18/06 2:10 PM Page 4 • GAS / ELECTRIC: Configures the thermostat to either gas/oil or electric heating systems. • C / F: Sets the display in either Celsius or Fahrenheit. • NORM / HP: Configures the thermostat for normal heating/cooling systems or heat pump systems (single stage). 10) Attach the thermostat body to the back plate by resting the top of the thermostat body on the two clips on the upper portion of the back plate.
70803-IM 12/18/06 2:10 PM Page 5 4) Set the system switch to the HEAT position and depress the red arrow key until the temperature set point is at least 3 degrees above the room temperature. The LCD will display a flame icon to indicate heat. The heating system should start within several seconds (the system blower may not come on immediately). 5) Set the system switch to the OFF position. The system should shut down within several seconds. The LCD will again display only the room temperature.
70803-IM 2) 12/18/06 2:10 PM Page 6 When the desired setting is made, release the key and the unit will automatically store the setting after 5 seconds. Cooling Fan Time Delay is factory set at 60 seconds. When the thermostat is set in the COOL position, the system blower will continue to circulate air for a period of 60 seconds after the compressor(s) has shut off. This feature can be adjusted.
0803-IM 12/18/06 2:10 PM Page 7 Understanding Additional Features • High Temperature Protection: While in the HEAT position, if the room temperature reaches 93 F (34 C), the thermostat will automatically shut off. In the unlikely event the room temperature reaches 99 F (37 c), a mechanical bimetal switch will shut off the thermostat. • Low Temperature Protection: While in the HEAT position, if the room temperature drops below 40 F (4 C), the thermostat will automatically initiate a call for heat.
70803-IM 12/18/06 2:10 PM Page 8 Troubleshooting SYMPTOM Display is blank CORRECTIVE ACTION Install 2 fresh AA Alkaline batteries No heat Set system switch to HEAT and raise set point above room temperature. Check thermostat wiring and connections. Check pilot light or HSI system on furnace. No cool Set SYSTEM switch to COOL and lower set point below room temperature. If snowflake is blinking, allow the 5 minute compressor lock-out to expire. Check thermostat wiring & connections.
70803-IM 12/18/06 2:10 PM Page 9 (Troubleshooting cont.) SYMPTOM System fan runs continuously CORRECTIVE ACTION Set fan switch to AUTO. Check thermostat wiring & connections. HI is displayed Reduce room temperature or allow a newly installed thermostat to acclimate. HI indicates a room temperature reading greater than 90 F (32 C). LO is displayed Increase room temperature or allow a newly installed thermostat to acclimate. LO indicates a room temperature reading less than 45 F (7 C).
70803-IM 12/18/06 2:10 PM Page 10 Wiring Diagrams Typical 5-Wire System RC RH G Y W FAN CONTROL COOL CONTROL HEAT CONTROL B O HOT HEAT 24 VAC TRANSFORMER HOT COM COOL 24 VAC TRANSFORMER COM Inst 10
70803-IM 12/18/06 2:10 PM Page 11 Wiring Diagrams Typical Single Stage Heat Pump System RC RH Install Jumper G Y Install Jumper FAN CONTROL COMPRESSOR CONTROL HOT B W 24 VAC TRANSFORMER O REV. VALVE COOL ENERGIZED REV.
70803-IM 12/18/06 2:10 PM Page 12 Wiring Diagrams Typical 2-Wire Millivolt System RC RH G Y W B O HEAT CONTROL COM HOT 24 VAC TRANSFORMER C TR 12 In
70803-IM 12/18/06 2:10 PM Page 13 Wiring Diagrams Typical 4-Wire System RC Install Jumper RH G Y FAN CONTROL COOL CONTROL HOT 24 VAC TRANSFORMER W B O HEAT CONTROL COM C T 13
70803-IM 12/18/06 2:10 PM Page 14 14
70803-IM 12/18/06 2:10 PM Page 15 Warranty ONE YEAR LIMITED WARRANTY Motors & Armatures Inc. warrants each new MARS thermostat against any defects due to non-conforming material or workmanship for a period of one year after the original date of purchase by a professional service technician and does not include the cost of removal or re-installation. This warranty extends to the contractor or dealer who purchased the product from a wholesaler.
70803-IM 12/18/06 2:10 PM Page 16 INSTALLATION AND OPERATING INSTRUCTIONS Non-Programmable Electronic Thermostat Heat/Cool Model 70803 ®
