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®
TRADELINE
T874A-F Multistage
Thermostats/Q674A-E,G Subbases
Installation Instructions for the Trained Service Technician.
Installation
Application
The T874A-F Thermostats provide 24 to 30 Vac control
WHEN INSTALLING THIS PRODUCT…
for heating and/or cooling systems as listed in Table 1.
1. Read these instructions carefully. Failure to follow
them could damage the product or cause a hazardous condi-
tion.
TABLE 1—THERMOSTAT HEATING AND/OR
2. Check the ratings given in the instructions and on the
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3. Secure the cover plate (if used) and subbase with the screws provided. Do not fully tighten the subbase screws. Fig. 1—Installation of subbase on outlet box. 4. Level the subbase using a spirit level, as shown in Fig. 3, and firmly tighten subbase mounting screws. The subbase mounting holes provide for minor out-of-level adjustments. IMPORTANT: An incorrectly leveled subbase will cause the temperature control to deviate from setpoint. Fig. 3—Subbase components and leveling procedure. For a wa
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TABLE 3—JUMPER APPLICATIONS. Fig. 6—Jumper adjacent terminals for special If your subbase has: Application Use Fig. system hookup. Strip wire 3/4 in. [19 mm]. RC, RH terminals single transformer 5 system adjacent terminals special system 6 operation or LED nonadjacent indication 7 terminals 3. Firmly tighten each terminal screw. 4. Fit wires as close as possible to the subbase. Push excess wire back into the hole. 5. Plug hole with nonflammable insulation to prevent drafts from affecting the the
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Fig. 8—T874A-D/Q674A in standard heating/cooling system. Fig. 9—T874C,D/Q674B in standard heating/cooling system with separate transformers for heating and cooling. SUBBASE SYSTEM COMPONENTS THERMOSTAT L1 RH (HOT) HEAT RELAY 1 L2 3 1 W1 1 FAN H1 SWITCH HEAT RELAY 2 FALL AUTO W2 H1 ANTICIPATOR HEAT CHANGEOVER ON VALVE B 4 X1 H2 6 FALL H2 ANTICIPATOR SYSTEM O SWITCH COOL CHANGEOVER 8 VALVE HEAT C1 RISE G OFF FAN RELAY 9 2 COOL Y2 COMPRESSOR 10 CONTACTOR 2 C1 ANTICIPATOR Y1 C2 ANTICIPATOR 11 COMP
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Fig. 10—T874D/Q674B in standard heating/cooling system with single transformer for heating and cooling. Exact replacement for York model no. 2TB04700324. Fig. 11—T874D,E,F/Q674C in standard heating/cooling system. 5 60-1165—6
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Fig. 12—T874A,D,F/Q674D in standard heating/cooling system. Fig. 13—T874D/Q674E in standard heating/cooling system. 6 60-1165—6
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Fig. 14—T874A-F/Q674G in standard heating/cooling system. Fig. 15—T874C/Q674B in standard application. 7 60-1165—6
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Fig. 16—Typical Q674 terminal designations. The thermostat and subbase used determines the number of system components controlled. TEMPERATURE LEVER STOPS INSTALL AND ADJUST LOCKING LEVER Some thermostats have factory-installed temperature SCREWS lever locking screws (Fig. 17) and/or stop brackets The two screws with insulated heads should be used (Fig. 18). Use these only if the HEAT and COOL tempera- only if the HEAT and COOL levers are to be locked in ture set point lever ranges are to be res
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9. Firmly tighten the mounting screw. MOUNTING THE THERMOSTAT 10. If the HEAT and COOL levers are to be locked in 1. Remove the thermostat cover by pulling the bottom place at a specific temperature, use the two insulated head edge of the cover upward until it snaps free of the cover clip. screws supplied instead of the two adjustable lever stop brackets. NOTE: The cover is hinged at the top and must be removed by pulling up at the bottom. 2. Carefully remove and discard the polystyrene packing
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2. Move the system switch to AUTO or HEAT (if SUBBASE SETTING used). The subbase switching positions control the system 3. After one minute, read the ammeter and record the operation as described below (Fig. 23). reading: SYSTEM SWITCH (some subbases do not have all of Stage 1: __________ amperes. the following functions): Stage 2: __________ amperes. OFF: Both the heating and cooling systems are off. If the fan switch is in AUTO position, fan is also off. NOTE: If equipment cycles too fast, set
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NOTE: Hand heat will offset the thermometer reading. Calibration After making each adjustment, wait ten minutes for the thermometer to stabilize before comparing. THERMOSTAT T874 Thermostats are accurately calibrated at the factory. They do not have provision for field calibration. Fig. 24—Thermometer calibration. THERMOMETER The thermometer in the thermostat has been accurately calibrated at the factory. The thermometer should need ad- justment only if it has been dropped or shifted due to mish
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Automation and Control Solutions Honeywell International Inc. Honeywell Limited—Honeywell Limitée 1985 Douglas Drive North 35 Dynamic Drive Golden Valley, MN 55422 Scarborough, Ontario M1V 4Z9 www.honeywell.com/yourhome 12 60-1165—6
