If control power is lost in an HVAC system, what is the expected outcome for room temperature?

When control power is lost in an HVAC system, the expected outcome for room temperature is a rise or increase in temperature. Without control power, the heating, ventilation, and air conditioning system can no longer operate, which means it can’t provide the necessary cooling or heating to maintain the desired temperature setpoint.

In a typical HVAC system, when the cooling system is active and functioning, it removes heat from the indoor environment, ensuring a comfortable temperature. Conversely, if the heating system is working, it adds heat to maintain warmth. When the controls lose power, all active temperature regulation by the system ceases, and any ongoing cooling methods also stop, leading to an increase in room temperature due to heat gain from both internal sources (such as occupants and equipment) and external sources (like sunlight).

Thus, without any control or operational capabilities of the HVAC unit, the natural tendency is for the temperature to rise, especially if the environment continues to heat up due to solar gain or other factors.