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T874A,D Zone Thermostats/
Q674B,D,E Subbases
Installation Instructions for the Trained Service Technician.
See Table 1 for thermostat/subbase and system compatibil-
Application
ity; see Table 2 for thermostat specifications. For complete
Honeywell Trol-A-Temp System specification and appli-
These T874A,D Zone Thermostats and Q674B,D,E
cation information, refer to the system specification in-
Subbases provide 24 to 30 Vac temperature control in
cluded with the control panel.
Honeywell Trol-A-Temp
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Installation Fig. 1—Installation of subbase on outlet box. WHEN INSTALLING THIS PRODUCT… 1. Read these instructions carefully. Failure to fol- low them could damage the product or cause a hazard- ous condition. 2. Check the ratings given in the instructions and on the product to make sure the product is suitable for your HORIZONTAL OUTLET application. BOX 1 3. Installer must be a trained, experienced service SUBBASE technician. 1 NOT INCLUDED WITH UNIT. M3703 4. After installation is complete, c
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letter code is located near each subbase terminal for identi- fication. The terminal barrier permits straight or conven- Fig. 5—Jumper RC and RH terminals for single transformer system. Strip wire 3/4 in. [19 mm]. tional wraparound wiring connection (Fig. 4). 2. Some Q674 Subbases have RC and RH terminals for isolated heating and cooling transformers. For zoning systems, jumper RC and RH terminals as shown in Fig. 5 and wire as single R terminal. 3. Firmly tighten each terminal screw. 4. Fit wir
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MOUNTING THE THERMOSTAT spring fingers are not bent flat, preventing proper electri- 1. Remove the thermostat cover by pulling the bottom cal contact with the subbase. edge of the cover outward away from the base until it snaps 4. Set the heat anticipator indicator(s) to 0.1A for free from the cover clip. proper system operation (Fig. 11). 5. Note the two tabs on the top inside edge of the NOTE: The cover is hinged at the top and is removed by thermostat base. The tabs fit into the corresponding
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Fig. 8—Typical hookup for MABS II and MABS II-L Control Panels with T874D Thermostat/Q674B,D Subbases in multistage heating-cooling zone system. MABS II Control Panel shown; MABS II-L Control Panel hookup is the same. T874D THERMOSTAT/ T874D THERMOSTAT/ Q674D SUBBASE Q674D SUBBASE T874D THERMOSTAT/Q674B SUBBASE 2 344 2 24 RC OG BY2 W2 Y1 RH W1 RC Y2 W2 Y1 RH W1 RC Y2 W2 Y1 RH W1 MABS II CONTROL PANEL SECOND EM. HEAT FAN HEAT COOL CAC ZONE 1 ZONE 2 ZONE 3 STAGE RELAY RELAY RELAY RELAY RELAY REL
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Fig. 9—Typical hookup for MABS XX Control Panel with T874A Thermostat/Q674B,E Subbases in single- stage heating-cooling zone system. MABS XX CONTROL PANEL ZONE 1 ZONE 2 ZONE 3 HEAT FAN COOL HEAT FAN COOL HEAT FAN COOL 1 MCM 2 CAC FC 3 ZONE 1 ZONE 2 ZONE 3 4 FAN FAN FAN ZONE SYS ZONE SYS ZONE SYS 5 6 DAMPER DAMPER DAMPER 7 TO SINGLE- 8 STAGE YW G Gh O B RC RH OPEN CLOSE OPEN CLOSE OPEN CLOSE HEATING/ 9 COOLING EQUIPMENT ZONE 1 ZONE 2 ZONE 3 M4 12 GY R W M6 M4 M1 VO VC G YR
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r
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Settings
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Checkout Before beginning checkout of thermostat operation, To set up the system for thermostat checkout, adjust set switches on the control panel for the desired system each thermostat settings as shown in Table 5. operation. See instructions provided with the control panel. TABLE 5—SYSTEM SET-UP FOR THERMOSTAT CHECKOUT. Heating Cooling Control Zones Other Zones Other Panel Zone 1 Than Zone 1 Zone 1 Than Zone 1 Mini-zone Set thermostat Move the heating set Set thermostat Move the cooling set MA
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Calibration Fig. 14—Thermometer calibration. THERMOSTAT T874 thermostats are accurately calibrated at the factory. They do not have provision for field calibration. THERMOMETER The thermometer in your thermostat has been accu- rately calibrated at the factory. The thermometer should only need adjustment if it has been dropped or shifted due to mishandling. If the set point lever and the thermometer reading do not agree: 1. Remove the thermostat cover by pulling up from the bottom of cover until
