Bryant Q674 - Manuals
Bryant Q674 – Manual in PDF format online.
Manuals:
Manual Bryant Q674
Summary
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 2 ORDERING INFORMATION When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the TRADELINE® Catalog or price sheets for complete ordering number. If you have additional questions, need f...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 3 60-2485—8 Standard Models T874 THERMOSTATS Models: See Table 3. Electrical Rating: 24 to 30 Vac. Switching: Coiled bimetal elements operate mercury switches. Temperature Adjustment: Heating and cooling setting levers, with separate scales located on to...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 7 60-2485—8 MERCURY NOTICE This control contains mercury in a sealed tube. Do not place control in the trash at the end of its useful life. If this control is replacing a control that contains mercury in a sealed tube, do not place your old control in th...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 8 Fig. 5. Installing Q674 Subbase on wall. Fig. 6. Subbase components and leveling procedure. Wire Subbase Disconnect power supply before beginning installation to prevent electrical shock or equipment damage. All wiring must comply with local ...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 11 60-2485—8 8. Move the HEAT and COOL levers to the maximum tem-perature desired. 9. Slide the stop brackets until one rests against the HEAT lever and the other against the COOL lever. 10. Firmly tighten the mounting screw. 11. If the HEAT and COOL lev...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 12 anticipator at 140 percent of the actual primary con-trol current draw to reduce the cycling rate. See Fig. 11. Most heat pump systems should cycle 2-1/2 to 3 times per hour. 4. Hang the upper edge of the thermostat cover on top of the therm...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 13 60-2485—8 Each mark on the scale represents 1°F (0.6°C) The differential is factory set at 2°F (1°C) the differential can be set as high as 12°F (7°C) To set the adjustable interstage differential, loosen the tension screw. See Fig. 13. Slide the adju...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 14 Move the system switch on the Q674 Subbase to COOL or AUTO. Move the cool setting lever on the T874 Multistage Thermostat about 10°F (6°C) below room temperature. See Fig. 12. The cooling equipment and fan should start. If the system has two...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 21 60-2485—8 OPERATION Heat Anticipation/Cool Anticipation When controlling a heating unit with a thermostat, the temperature does not remain exactly at the thermostat setpoint, but varies within a certain temperature range. Heat anticipation is added to...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 22 CAUTION Equipment Damage Hazard. Due to calibration techniques used for T874 Thermostats with outdoor reset, the C815A Thermistor must be wired into the system at all times. Failure to do so will result in serious degradation of performance....
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 23 60-2485—8 Fig. 31. System switching for automatic changeover. Automatic changeover is frequently used in areas where there are large temperature differences in 24 hours. Some uses for the automatic changeover feature are in the southern states (cool i...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 24 one controlling the auxiliary heat) makes only when the heat pump alone cannot handle the load. That is how the strategy of using the most economical heat first is implemented. Cycling Rate Normally, thermostat anticipation is set to cycle a...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 25 60-2485—8 Low Temperature Lockouts Some manufacturers of heat pumps have previously controlled their units so the compressor was locked out below a specified outdoor temperature. This was done because of the stress placed on the compressor by the very...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 26 Defrost Control In some regions, during half or more of the heating season, the outdoor coil operates below 32°F (0°C) Frost or ice builds up on the outdoor coil of a heat pump similarly to the frost buildup in a household refrigerator. Even...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 27 60-2485—8 Fig. 39. Auxiliary heat in two-stage thermostat. This method keeps the auxiliary heat off until the heating load is large enough to demand 100 percent heat pump operation. That demand is measured by the thermostat and is the actual heat requ...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 28 the thermostat. A set of contacts on the emergency heat relay is used to bypass each outdoor thermostat so that all electric heat is under immediate thermostat stage-two control. So the emergency heat relay simply bypasses the outdoor thermo...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 29 60-2485—8 CROSS REFERENCE The following section lists the current T874 Trade replace-ments for T872 and T874 Multistage Thermostats. It also lists the Q674 Trade replacements for Q672 and Q674 Subbases. All thermostats listed carry the Honeywell logo ...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 74 C1207 78 Obsolete. Friedrich; System: OVERRIDE-AUTO-OFF; used with T874P1014. T8600D2028 (programmable) Wiring differences (old=new): L=R, W=O; W-Y jumper required; night setback. C1215 97 Obsolete. Friedrich part no. AQ5315; System: OVERRID...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 96 WIRING DIAGRAMS Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications. Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications. H1 FALL L1 (HOT) L2 1 RH W1 W2 O G Y2 Y1 RC HEAT ...
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