After replacing a belt drive motor, the furnace continuously shuts off due to limit control. What is the likely reason?

The situation described involves a furnace that continuously shuts off due to limit control after a belt drive motor replacement. When considering the possibility of the motor running in the wrong direction, this can directly affect airflow within the heating system. If the motor is not rotating in the correct direction, it will not effectively circulate air through the furnace and ductwork, leading to inadequate airflow.

When airflow is insufficient, the heat exchanger can overheat since warm air is not being moved efficiently throughout the system. This overheating triggers the limit switch, which is a safety mechanism designed to prevent damage to the unit from excessive heat. The limit control will shut down the furnace to protect its components when it detects high temperatures.

In contrast, while issues such as voltage problems, thermostat calibration, or obstructions in the blower could similarly cause operational issues, they do not specifically relate to the motor's direction impacting the airflow that leads to a limit control shutdown. Thus, if the motor is indeed running backwards, it will most likely cause the system to fail to maintain the necessary air circulation and trigger the limit safety device, leading to repeated shut-offs.