Installation Instructions
Page 1
... the thermostat. radiant heat from affecting the thermostat; Place the wallplate at average temperature. Registered Trademark Copyright © 2004 Honeywell International Inc. • • All Rights Reserved 69-1740 MERCURY NOTICE If this Product... 1. The thermostat functions normally...hot or cold air from heat to prevent drafts from the sun or appliances. - T8400C, T8401C Electronic Thermostats INSTALLATION INSTRUCTIONS The T8400C and T8401C Thermostats provide singlestage, non-programmable temperature control for 24V heating-cooling systems with manual changeover...
... the thermostat. radiant heat from affecting the thermostat; Place the wallplate at average temperature. Registered Trademark Copyright © 2004 Honeywell International Inc. • • All Rights Reserved 69-1740 MERCURY NOTICE If this Product... 1. The thermostat functions normally...hot or cold air from heat to prevent drafts from the sun or appliances. - T8400C, T8401C Electronic Thermostats INSTALLATION INSTRUCTIONS The T8400C and T8401C Thermostats provide singlestage, non-programmable temperature control for 24V heating-cooling systems with manual changeover...
Installation Instructions
Page 2
T8400C, T8401C ELECTRONIC THERMOSTATS YES NO NO 5 FEET [1.5 METERS] NO M11338 Fig. 1. M12202A Fig. 2. Mounting wallplate to prevent electrical shock or equipment damage. This is an electric heat system, set the switch to the E position. Fan operation (fuel) switch. 69-1740 2 Typical location of thermostat, restrict all wiring to Fig. 6 through 10 for most systems...
T8400C, T8401C ELECTRONIC THERMOSTATS YES NO NO 5 FEET [1.5 METERS] NO M11338 Fig. 1. M12202A Fig. 2. Mounting wallplate to prevent electrical shock or equipment damage. This is an electric heat system, set the switch to the E position. Fan operation (fuel) switch. 69-1740 2 Typical location of thermostat, restrict all wiring to Fig. 6 through 10 for most systems...
Installation Instructions
Page 3
...) Rc R W Y B O M13274 Fig. 5. G Rc R 24 W B Y O 1 L1 (HOT) L2 FAN RELAY 3 COOL DAMPER 3 HEAT DAMPER COMPRESSOR CONTACTOR HEAT RELAY 1 L1 (HOT) L2 COOLING TRANSFORMER HEATING TRANSFORMER 1 POWER SUPPLY. Typical hookup of T8400C in single-stage heat pump systems. 3 69-1740 T8400C, T8401C ELECTRONIC THERMOSTATS KEEP WIRING IN SHADED AREA G Rc R W B Y O MOUNTING SCREW HOLE WIRING ENTRANCE HOLE MOUNTING...
...) Rc R W Y B O M13274 Fig. 5. G Rc R 24 W B Y O 1 L1 (HOT) L2 FAN RELAY 3 COOL DAMPER 3 HEAT DAMPER COMPRESSOR CONTACTOR HEAT RELAY 1 L1 (HOT) L2 COOLING TRANSFORMER HEATING TRANSFORMER 1 POWER SUPPLY. Typical hookup of T8400C in single-stage heat pump systems. 3 69-1740 T8400C, T8401C ELECTRONIC THERMOSTATS KEEP WIRING IN SHADED AREA G Rc R W B Y O MOUNTING SCREW HOLE WIRING ENTRANCE HOLE MOUNTING...
Installation Instructions
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.... 11. Use for most systems). M20881 Fig. 9. Typical hookup of the thermostat to Wallplate 1. In heating, the fan is controlled directly by using an electric heat thermostat, the fan starts and stops with the cooling equipment. T8400C, T8401C ELECTRONIC THERMOSTATS G C R W B Y O 1 L1 (HOT) 24V L2 TRANSFORMER HEAT RELAY COOL RELAY FAN RELAY 1 POWER SUPPLY. DASHED LINES INDICATE TABS...
.... 11. Use for most systems). M20881 Fig. 9. Typical hookup of the thermostat to Wallplate 1. In heating, the fan is controlled directly by using an electric heat thermostat, the fan starts and stops with the cooling equipment. T8400C, T8401C ELECTRONIC THERMOSTATS G C R W B Y O 1 L1 (HOT) 24V L2 TRANSFORMER HEAT RELAY COOL RELAY FAN RELAY 1 POWER SUPPLY. DASHED LINES INDICATE TABS...
Installation Instructions
Page 5
...: 1. If the room temperature is displayed in the lower right corner of the thermostat to test heat or cool outputs. M14685 2. INCREASE SETTING DECREASE SETTING T8400C, T8401C ELECTRONIC THERMOSTATS 3. The ▼ indicator points to Set when the temperature setpoint is displayed. ... degrees. Press the ▲▼ keys simultaneously for approximately five seconds as follows: Cool: The thermostat controls the cooling system. Heat: The thermostat controls the heating system. Each press changes the setpoint one degree; To set the temperature setpoint to 11°C....
...: 1. If the room temperature is displayed in the lower right corner of the thermostat to test heat or cool outputs. M14685 2. INCREASE SETTING DECREASE SETTING T8400C, T8401C ELECTRONIC THERMOSTATS 3. The ▼ indicator points to Set when the temperature setpoint is displayed. ... degrees. Press the ▲▼ keys simultaneously for approximately five seconds as follows: Cool: The thermostat controls the cooling system. Heat: The thermostat controls the heating system. Each press changes the setpoint one degree; To set the temperature setpoint to 11°C....
Installation Instructions
Page 6
...ELECTRONIC THERMOSTATS NOTE: In installer setup mode only, each press of a time delay relay or through the use only. Stop scrolling when the desired rate is shown, but information displayed varies by model) is displayed. C3 = Aggressive heating/cooling temperature control (can cause room temperature to scroll between 1, 3, 4, 5, 6, 9, or 12. M18420 CHECKOUT Heating...the system turns on initial startup, the T8400C and T8401C Thermostats go into a five-minute delay. When using an electric heat thermostat, the fan starts immediately. 3. This information is below ...
...ELECTRONIC THERMOSTATS NOTE: In installer setup mode only, each press of a time delay relay or through the use only. Stop scrolling when the desired rate is shown, but information displayed varies by model) is displayed. C3 = Aggressive heating/cooling temperature control (can cause room temperature to scroll between 1, 3, 4, 5, 6, 9, or 12. M18420 CHECKOUT Heating...the system turns on initial startup, the T8400C and T8401C Thermostats go into a five-minute delay. When using an electric heat thermostat, the fan starts immediately. 3. This information is below ...
Installation Instructions
Page 7
... equipment responds correctly to raise the temperature setting above the room temperature. T8400C, T8401C ELECTRONIC THERMOSTATS Fan 1. In cooling, the fan starts and stops with the heating equipment. The fan should shut down. Press the ▲ key to the thermostat. 7 69-1740 NOTE: To bypass the five-minute delay, see the Optional System Checkout...
... equipment responds correctly to raise the temperature setting above the room temperature. T8400C, T8401C ELECTRONIC THERMOSTATS Fan 1. In cooling, the fan starts and stops with the heating equipment. The fan should shut down. Press the ▲ key to the thermostat. 7 69-1740 NOTE: To bypass the five-minute delay, see the Optional System Checkout...
