70802-IM 12/14/06 3:11 PM Page 2 WARNING! • To prevent electrical shock and/or equipment damage, disconnect electric power to system at main fuse or cir- cuit breaker box until installation is complete. • This thermostat is for use on 24 VAC multi-stage heat pump systems.
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70802-IM 12/14/06 3:11 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.
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70802-IM 12/14/06 3:11 PM Page 4 8) Carefully attach the thermostat wires to the appropriate connections on the terminal board on the back plate. Use the notes taken from step 2 of Removing The Existing Thermostat to determine their location on the new thermostat.
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70802-IM 12/14/06 3:11 PM Page 5 2) Set the fan switch to the ON position. The system blower should start. 3) Set the fan switch to the AUTO position. The system blower should stop. 4) Set the system switch to the HEAT position and depress the red...
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70802-IM 12/14/06 3:11 PM Page 6 1) With the system setting in the OFF position, simultaneously depress the red and blue arrow keys. The LCD (liquid crystal Image shows temperature display) will display the temperature differential setting. Using differential setting of 0.5.
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70802-IM 12/14/06 3:11 PM Page 7 Understanding Additional Features • High Temperature Protection: While in the HEAT setting, 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.
70802-IM 12/14/06 3:11 PM Page 8 Troubleshooting SYMPTOM CORRECTIVE ACTION Display is blank Check thermostat wiring & connections. Check circuit breaker/fuse panel. No heat Set system switch to HEAT and raise set point above room temperature. Check thermostat wiring and connections.
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70802-IM 12/14/06 3:11 PM Page 9 (Troubleshooting cont.) SYMPTOM CORRECTIVE ACTION System fan runs continuously 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).
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.
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