INTELLIGENT HVAC CONTROL INCLUDING AUTOMATIC FURNACE SHUTDOWN EVENT PROCESSING

摘要

This patent specification relates to methods and systems that can detect over cycling conditions that exist in an HVAC system. The over cycling condition can be caused by overheating of a forced air heating system or furnace of the HVAC system control. When the furnace overheats, a thermally actuated limit switch within the furnace may cut off power to a heat generation apparatus. The limit switch can reconnect the power to the heat generation apparatus after it has cooled down, at which point the thermostat control system may issue another heating call to continue heating the enclosure so that it reaches the desired temperature. If the overheat condition persist, then the thermally actuated switch will cut power, resulting in repeated power cycling. The detection system and methods can monitor these power loss events and use them as data points for determining whether an alert condition exists within the HVAC system.

主权项

1. A method for controlling a HVAC (heating, ventilation, and air conditioning) system that uses forced air heating, the method implemented in a thermostat, the method comprising:
during a moving window of heat cycles, wherein each heat cycle is called by the thermostat to instruct the HVAC system to generate forced air heating from a start time to an end time:
calculating a mean duration of a fixed number of provoking heat cycles, wherein a provoking heat cycle is characterized by a premature end time caused by a HVAC system induced power loss;determining whether an alert condition exists by comparing a ratio of the number of provoking heat cycles that exceed the mean duration and the number of heat cycles that exceed the mean duration to an alert threshold; andconfirming that the alert condition exists if the ratio exceeds the alert threshold and at least one non-alert condition is not satisfied. each heat cycle is called by the thermostat to instruct the HVAC system to generate forced air heating from a start time to an end time.