Intelligent HVAC control including automatic furnace shutdown event processing

Patent metadata

Field	Value
Publication number	US-10544946-B2
Application number	US-201815918510-A
Country	US
Kind code	B2
Filing date	Mar 12, 2018
Priority date	Aug 21, 2015
Publication date	Jan 28, 2020
Grant date	Jan 28, 2020

Abstract

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.

First claim

What is claimed is:

1. A method for controlling a HVAC (heating, ventilation, and air conditioning) system that uses a furnace system for forced air heating, the method implemented in a thermostat, the method comprising:
instructing the HVAC system to generate forced air heating during a heating cycle call spanning from a start time to an end time;
monitoring that the HVAC system prematurely shuts itself down prior to the end time, wherein:
the HVAC system shut down is caused by a furnace system induced power loss;
monitoring the HVAC system comprises determining that a plurality of repeated premature HVAC system shutdowns occur during a plurality of heating cycle calls; and
determining that the plurality of repeated premature HVAC system shutdowns occur during the plurality of heating cycle calls comprises:
verifying that a number of the plurality of repeated premature HVAC system shutdowns exceeds an alert threshold within a timeframe including a subset of the plurality of heating cycle calls; and
verifying that the number of the plurality of repeated premature HVAC system shutdowns is less than a non-alert threshold, wherein no alert condition is sent if the number of the plurality of repeated premature HVAC system shutdowns is less than a non-alert threshold; and

sending an alert condition notice in response to the monitored premature shutdown of the HVAC system.

2. The method of claim 1 , wherein the thermostat is connected to a plurality of HVAC wires corresponding to the HVAC system, wherein the determining comprises monitoring one of a plurality of HVAC wire connectors for a signal change while the HVAC system is executing the heating cycle call.

3. The method of claim 1 , wherein sending the alert comprises alerting occupants of a structure containing the HVAC system.

4. The method of claim 1 , wherein sending the alert comprises alerting at least one service repair technician.

5. The method of claim 1 , wherein sending the alert comprises an instruction to perform a corrective action.

6. A thermostat, comprising:
a plurality of HVAC (heating, ventilation, and air conditioning) wire connectors operative to receive a plurality of HVAC wires corresponding to an HVAC system comprising a forced air furnace; and
control circuitry operative to at least partially control operation of the HVAC system, wherein the control circuitry is further operative to:
instruct the HVAC system to generate forced air heating during a heating cycle call spanning from a start time to an end time;
monitor that the HVAC system prematurely shuts itself down prior to the end time, wherein:
the HVAC system shut down is caused by a furnace system induced power loss;
the control circuitry being operative to monitor the HVAC system comprises the control circuitry being further operative to determine that a plurality of repeated premature HVAC system shutdowns occur during a plurality of heating cycle calls; and
the control circuitry being operative to determine that the plurality of repeated premature HVAC system shutdowns occur during the plurality of heating cycle calls comprises the control circuitry being further operative to:
determine that a number of the plurality of repeated premature HVAC system shutdowns exceeds an alert threshold within a timeframe including a subset of the plurality of heating cycle calls; and
determine that the number of the plurality of repeated premature HVAC system shutdowns is less than a non-alert threshold, wherein no alert condition is sent if the number of the plurality of repeated premature HVAC system shutdowns is less than a non-alert threshold; and

send an alert condition notice in response to the monitored premature shutdown of the HVAC system.

7. The thermostat of claim 6 , wherein the control circuitry is operative to monitor one of the plurality of HVAC wire connectors for a signal change while the HVAC system is executing the heating cycle call.

8. The thermostat of claim 6 , wherein the control circuitry is operative to send the alert to alert occupants of a structure containing the HVAC system.

9. The thermostat of claim 6 , wherein the control circuitry is operative to send the alert to at least one service repair technician.

10. The thermostat of claim 6 , wherein the alert comprises an instruction to perform a corrective action.

Assignees

• Google Llc

Inventors

• Stefanski Mark
• Pellat Marie

Classifications

• G06F1/00

  Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00 (architectures of general purpose stored program computers G06F15/76) · CPC title

• G05D23/1917

  using digital means · CPC title

• F24F11/30

  for purposes related to the operation of the system, e.g. for safety or monitoring · CPC title

• F24F2110/10

  Temperature · CPC title

• G05B15/02

  electric · CPC title