The T874R Thermostat and Q674L Subbase provide 24 to 30 Vac control of 2-stage heating and 1-stage cool-ing heatpump systems with manual changeover. Q674L Subbase provides EM.HT.-HEAT-OFF-COOL system switching andAUTO-ON fan switching. See Table 1 for specific T874R/Q674L combinations Model:Q674A-E Page: 12 Model:Q674B Page: 8 Note: For opening this Honeywell Thermostat Q674 User Manual, your … Continue reading Honeywell Thermostat Q674 User Manual