Manual | Thermotech Tt-91

| Option | Setting | Description | |--------|---------|-------------| | 1 | Fahrenheit (°F) or Celsius (°C) | Default: °F | | 2 | 12h or 24h time format | Default: 12h | | 3 | 5/2 (weekday/weekend) or 7-day programming | Default: 5/2 | | 4 | Standard heat/cool or heat pump (O/B) – select | TT-91 uses STd | | 5 | Cycle rate: FA (fast) or SL (slow) for heating | Default: FA | | 6 | Compressor delay: 5 (min) or 0 | Default: 5 | | 7 | Temperature differential (0.5°–2°F) | Default: 1°F | | 8 | Backlight: On or Off | Default: On | | 9 | Factory reset (select YES) | – |

1. Introduction & Overview The ThermoTech TT-91 is a 7-day, 5/1/1 or 5/2 programmable digital thermostat designed for conventional single-stage heating and cooling systems (gas, oil, electric, or forced air). It is not compatible with heat pumps (without modification), multi-stage systems, or millivolt (floor/wall gas) systems unless explicitly stated. thermotech tt-91 manual

A: You likely have a program schedule active. Press HOLD to override temporarily, or reprogram periods to match your needs. A: You likely have a program schedule active

A: Once per year, or when BATT appears. Without a C wire, batteries last ~12 months. Without a C wire, batteries last ~12 months