HVAC System Mode Detection Based On Control Line Current

• US 20150362207A1
• Filed: 05/19/2015
• Published: 12/17/2015
• Est. Priority Date: 06/12/2014
• Status: Active Grant

• Current Assignee: Emersub Cxiii Incorporated (Emerson Electric Company)
• Original Assignee: Emerson Electric Company
• Inventors: ABIPROJO, Priotomo, ARENSMEIER, Jeffrey N.
• Granted Patent: US 10,670,293 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/32 Responding to malfunctions or emergencies
• CPC Class Codes: F24F 11/52 Indication arrangements, e.g. displays
• CPC Class Codes: F24F 11/56 Remote control
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/65 for selecting an operating mode
• CPC Class Codes: F24F 11/66 Sleep mode
• CPC Class Codes: F24F 11/67 Switching between heating and cooling modes
• CPC Class Codes: F24F 2110/00 Control inputs relating to air properties
• CPC Class Codes: F24F 2140/50 Load

Abstract

A monitoring system for monitoring a heating, ventilation, and air conditioning (HVAC) system of a building includes a monitoring server. The monitoring server is configured to receive an aggregate control line current value from a monitoring device. The aggregate control line current value represents a total current flowing through control lines used by a thermostat to command the HVAC system. The monitoring server is configured to determine a commanded operating mode of the HVAC system in response to the aggregate control line current value. Operating modes of the HVAC system include at least one of an idle mode and an ON mode. The monitoring server is configured to analyze a system condition of the HVAC system based on the determined commanded operating mode.

Claims

1. A monitoring system for monitoring a heating, ventilation, and air conditioning (HVAC) system of a building, the monitoring system comprising:

a monitoring server configured to;

receive an aggregate control line current value from a monitoring device, wherein the aggregate control line current value represents a total current flowing through control lines used by a thermostat to command the HVAC system;

determine a commanded operating mode of the HVAC system in response to the aggregate control line current value, wherein operating modes of the HVAC system include at least one of an idle mode and an ON mode; and

analyze a system condition of the HVAC system based on the determined commanded operating mode.

2. The monitoring system of claim 1 wherein the system condition includes at least one of a detected fault of the HVAC system and a predicted fault of the HVAC system.

3. The monitoring system of claim 2 wherein the monitoring server is configured to generate an alert for at least one of a customer and a contractor in response to determining presence of at least one of the detected fault and the predicted fault.

4. The monitoring system of claim 1 wherein the monitoring server is located remotely from the building.

5. The monitoring system of claim 1 further comprising the monitoring device, wherein the monitoring device is installed at the building, and wherein the monitoring device is configured to measure the total current flowing through the control lines.

6. The monitoring system of claim 5 wherein the monitoring device includes a current sensor that measures a first current flowing through a conductor supplying power to the thermostat, wherein the monitoring device determines the aggregate control line current value based on the first current.

7. The monitoring system of claim 5 wherein:

the monitoring device includes a voltage sensor that measures a voltage on an output side of a transformer associated with the control lines,

the monitoring device determines the aggregate control line current based on an apparent transformer ratio, and

the apparent transformer ratio is based on the measured voltage of the output side of the transformer and a voltage on an input side of the transformer.

8. The monitoring system of claim 5 wherein the monitoring device includes a voltage sensor that measures a voltage associated with the control lines, and wherein the monitoring device determines the aggregate control line current based on the measured voltage.

9. The monitoring system of claim 5 further comprising a second monitoring device, wherein:

the second monitoring device includes a current sensor configured to measure an aggregate control line current consumed by an outdoor unit of the HVAC system; and

the monitoring server is configured to infer, in response to the commanded operating mode of the HVAC system being unknown, the commanded operating mode using the aggregate control line current consumed by the outdoor unit.

10. The monitoring system of claim 1 wherein the ON mode encompasses a plurality of operating modes including at least two of the following:

a fan only mode, a heating mode, a second stage heating mode, a cooling mode, a second stage cooling mode, an auxiliary heating mode, and an emergency mode.

11. The monitoring system of claim 1 wherein the monitoring server is configured to:

store a table of aggregate control line current values with respect to the operating modes of the HVAC system; and

determine the commanded operating mode of the HVAC system based on the table.

12. The monitoring system of claim 11 wherein the table includes an aggregate control line current value corresponding to each of the operating modes of the HVAC system.

13. The monitoring system of claim 12 wherein:

a first current value is associated with a first upper limit and a first lower limit in the table and corresponds to a first operating mode; and

the monitoring server is configured to determine that the commanded operating mode of the HVAC system is the first operating mode in response to the received aggregate control line current being greater than or equal to the first lower limit and less than or equal to the first upper limit.

14. The monitoring system of claim 11 wherein the table is predefined upon commissioning of the HVAC system.

15. The monitoring system of claim 11 wherein the table is predefined based on a model number of the HVAC system.

16. The monitoring system of claim 11 wherein the monitoring server is configured to populate the table.

17. The monitoring system of claim 1 wherein the monitoring server is configured to, in response to the commanded operating mode of the HVAC system being unknown, infer the commanded operating mode using additional data.

18. The monitoring system of claim 17 wherein the monitoring server is configured to store the inference along with the received aggregate control line current for future use.

19. The monitoring system of claim 17 wherein the additional data includes outside ambient temperature in a geographical region of the HVAC system.

20. The monitoring system of claim 17 wherein the additional data includes supply air temperature of the HVAC system.

21. The monitoring system of claim 17 wherein the additional data includes a refrigerant line temperature of the HVAC system.

22. The monitoring system of claim 17 wherein the additional data includes a time of year.

23. The monitoring system of claim 17 wherein the additional data includes an aggregate current consumption of the HVAC system.

24. The monitoring system of claim 23 wherein the aggregate current consumption of the HVAC system includes all current drawn by components of either (i) an indoor enclosure of the HVAC system or (ii) an outdoor enclosure of the HVAC system.

25. The monitoring system of claim 24 wherein the additional data includes at least one of:

a steady-state value of the aggregate current consumed by the indoor enclosure; and

a time-domain or frequency-domain signature of the aggregate current consumed by the indoor enclosure.