Thermotech Tt-91 Manual -

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.

A: You likely have a program schedule active. Press HOLD to override temporarily, or reprogram periods to match your needs. thermotech tt-91 manual

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