Honeywell T874 - Manuals
Honeywell T874 – Manual in PDF format online.
Manuals:
Manual Honeywell T874
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 60-2485—8 6 Optional Specifications (Q674 Only): Models available with up to four LEDs; for example, LEDs can show EM. HT, AUX. HT, SERVICE, CHECK, FILTER, and LOCKOUT. See Fig. 3. System switching marked HEAT-OFF/RESET-COOL for sys- tems requiring imped...
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 60-2485—8 10 Outdoor Disconnect The National Electrical Code requires the installation of a disconnect switch w ithin sight of the outdoor unit of an air conditioner or heat pump. The switch is for the safety of any technician working on the unit. The te...
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 le...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60-2485—8 12 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 thermostat base and swing the cover downward until it engages with the cover clip. Fig. 11. Adjustable heat anticipat...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 13 60-2485—8 smaller differential. In cooling, slide the lever closer together for a larger differential, or wider apart for a smaller differential. While supporting the scale with hand, tighten the tension screw. IMPORTANT Support the scale with hand wh...
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 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 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 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 30 A1279 General Electric logo; no. AY28X114A; 75°F stop; locking cover; no thermometer. T874A1010 Use T874A1176 for Dept. of Defense (DoD) application. A1287 General Electric; no. AY28X097A; fan current shunt for auto fan in heating; heat anti...
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 71 60-2485—8 Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. Description Q674 Trade Replacement Remarks Q674A System: HEAT-AUTO-COOL; Fan: AUTO-ON A1001 71 Standard OEM. Q674A1019 A1019 71 TRADELINE® model; used with T874A-D. Q674A1019 A1035...
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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