Which condition is critical after installing a thermostat?

After installing a thermostat, it is crucial to ensure that the capillary tube is positioned correctly because this tube plays a key role in sensing the ambient temperature. The capillary tube contains the thermometric fluid that expands or contracts with temperature changes, and its accurate positioning is essential for the thermostat to function effectively. If the capillary tube is improperly placed, it may lead to inaccurate temperature readings, causing the thermosat to malfunction by not turning the heating or cooling system on or off as required.

While the functionality of the display, temperature accuracy, and correct wiring are also important considerations, the immediate critical condition focuses on the capillary tube's placement, as it directly influences the thermostat's performance in responding accurately to temperature changes. If the capillary tube is off, all other components may appear to work correctly, but the thermostat will still fail to control the environment as needed.