THERMOSTAT CIRCUITRY FOR CONNECTION TO HVAC SYSTEMS

• US 20120126021A1
• Filed: 02/24/2011
• Published: 05/24/2012
• Est. Priority Date: 09/14/2010
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Nest Labs Incorporated (Alphabet Inc.)
• Inventors: WARREN, Daniel Adam, FIENNES, Hugo, DUTRA, Jonathon Alan, BELL, David, FADELL, Anthony Michael, ROGERS, Matthew Lee
• Granted Patent: US 9,605,858 B2
• Time in Patent Office: Days
• US Class Current: 236/1.C
• CPC Class Codes: B01D 46/0086 Filter condition indicators
• 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 11/39 Monitoring filter performance
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/47 Responding to energy costs
• CPC Class Codes: F24F 11/52 Indication arrangements, e.g. displays
• CPC Class Codes: F24F 11/56 Remote control
• CPC Class Codes: F24F 11/58 using Internet communication
• CPC Class Codes: F24F 11/61 using timers
• 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 11/64 using pre-stored data
• CPC Class Codes: F24F 11/89 Arrangement or mounting of control or safety devices
• CPC Class Codes: F24F 2110/00 Control inputs relating to air properties
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2120/10 Occupancy
• CPC Class Codes: F24F 2120/20 Feedback from users
• CPC Class Codes: F24F 2130/40 Noise
• CPC Class Codes: F24F 2140/00 Control inputs relating to system states
• CPC Class Codes: F24F 2140/60 : Energy consumption
• CPC Class Codes: G05B 13/0265 : the criterion being a learning criterion
• CPC Class Codes: G05B 15/02 : electric
• CPC Class Codes: G05D 23/19 : characterised by the use of electric means G05D23/1393 takes precedence
• CPC Class Codes: G05D 23/1902 : characterised by the use of a variable reference value
• CPC Class Codes: G05D 23/1917 : using digital means
• CPC Class Codes: H01R 9/2416 : Means for guiding or retaining wires or cables connected to terminal blocks
• CPC Class Codes: H04W 4/70 : Services for machine-to-machine communication [M2M] or machine type communication [MTC]
• CPC Class Codes: Y02B 10/20 : Solar thermal
• CPC Class Codes: Y02B 10/70 : Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
• CPC Class Codes: Y02D 30/70 : in wireless communication networks
• CPC Class Codes: Y10T 29/49826 : Assembling or joining

Abstract

A thermostat and related methods is provided for controlling an HVAC system having one or two separate transformers for supplying power to the HVAC system. The thermostat includes isolation circuitry housed within the thermostat to safely connect to the HVAC control wires and power wire(s) whether the HVAC system has one or two separate transformers without the use of removable jumpers or manual rewiring. The thermostat can include a processor that sends DC signals for turning on and turning off each of the HVAC functions, and an isolator adapted to electrically isolate the processor from the control wires and power wire(s). The isolator can include a transformer, such as a low cost Ethernet transformer. The circuitry can include one or more field effect transistors adapted and arranged so as to open or close an electrical connections between the control and power wires, thereby turning on or off the associated HVAC function. According to some embodiments, the Rc and Rh terminals are permanently connected using a fuse.

Claims

1. A thermostat for controlling an HVAC system having one or two transformers for supplying power to control the HVAC system, the HVAC system having at least one control wire for controlling one or more HVAC functions and one or two electrical power return wires each of which is electrically connected to one of the one or two separate transformers, the thermostat comprising:

a plurality of wiring terminals for making electrical connections to the at least one control wire and to the one or two power return wires; and

circuitry connected to the plurality of terminals, the terminals and circuitry being adapted an arranged such that the at least one control wire and the one or two power return wires can be connected whether the HVAC system has a one or two transformers without the use of removable jumpers or manual rewiring.

2. A thermostat according to claim 1 wherein the plurality of wiring terminals includes a first terminal adapted to accept one of the one or two electrical power return wires and a second terminal adapted to accept another of the one or two electrical power return wires, and the first wiring terminals includes a switch that automatically disrupts an electrical connection between the first and second terminals when presence of a wire connected to the terminal is detected.

3. A thermostat according to claim 2 wherein the second terminal includes a switch that automatically disrupts an electrical connection between the first and second terminals when presence of a wire connected to the terminal is detected, such that the switches of the first and second terminals cause electrical isolation between the first and second terminals when the presence of wires is detected by both first and second terminal, and cause an electrical connection between the first and second terminals when the presence of wires in both the first and second terminals is not detected.

4. A thermostat according to claim 1 further comprising:

one or more solid state switching components adapted and arranged to provide switching so as to turn on and off each of the HVAC functions;

a processor adapted and configured to send DC signals for turning on and turning off each of the HVAC functions using the one or more solid state switching components; and

an isolator positioned and adapted to electrically isolate the processor from one or more solid state switching components.

5. A thermostat according to claim 4 wherein the isolator includes a transformer.

6. A thermostat according to claim 4 wherein the isolator includes a capacitor.

7. A thermostat according to claim 4 wherein the one or more solid state switching components do not reference an electrical ground.

8. A thermostat according to claim 1 wherein the one or more solid state switching components includes one or more field effect transistors.

9. A thermostat according to claim 1 wherein the one or more HVAC functions include heating and cooling.

10. A thermostat according to claim 1 wherein two wiring terminals are included for two power return wires, and the two wiring terminals are electrically connected.

11. A thermostat according to claim 1 wherein the HVAC system is a residential HVAC system.

12. A thermostat according to claim 1 wherein the HVAC system is a light commercial HVAC system.

13. A thermostat according to claim 1 wherein one of the one or more HVAC functions is cooling and HVAC system has a cooling capacity of less than about 5 tons.

14. A thermostat according to claim 4 further comprising circuitry connected to the one or more solid state switching components, the circuitry and the solid state switching components adapted and arranged such that the switching is left in an open state in the event of a failure condition within the thermostat.

15. A thermostat according to claim 4 further comprising current sensing circuitry adapted and arranged to sense current passing through the one or more solid state switching components.

16. A thermostat according to claim 15 wherein the current sensing circuitry includes circuitry to measure a voltage differential across at least one of the solid state switching components.

17. A thermostat according to claim 15 wherein the current sensing circuitry includes measuring a voltage differential across a thermistor in series with at least one of the solid state switching components.

18. A thermostat for controlling an HVAC system having one or two transformers for supplying power to the HVAC system, the HVAC system having one or more control wires for controlling one or more HVAC functions and one or two electrical power wires each of which is electrically connected to one of the one or two transformers, the thermostat comprising:

two power return wiring terminals for making electrical connections to the one or two power return wires; and

a switching circuit for electrically connecting the two power return wiring terminals in cases where the HVAC system has only one power transformer and electrically disconnecting the two power return wiring terminals in cases where the HVAC system has two power transformers.

19. A thermostat according to claim 18 wherein the switching circuit includes one or more switches adapted to automatically electrically disconnect the two power return wiring terminals in cases where two electrical power wires are connected to the two power return wiring terminals.

20. A thermostat according to claim 19 wherein at least one of the one or more switches is mechanically actuated when a user makes connection of an electrical power wire to a power return wiring terminal.

21. A thermostat according to claim 18 wherein the circuitry includes one or more detection circuits adapted and arranged to detect whether the HVAC system has one or two power transformers.

22. A thermostat according to claim 18 wherein the switching circuit electrically connects or disconnects the two power return wiring terminals based at least in part on input from a user.

23. A thermostat according to claim 18 wherein the switching circuit includes a relay.

24. A thermostat according to claim 18 wherein the switching circuit includes one or more solid state switching components.

25. A thermostat for controlling an HVAC system having one or more HVAC functions, the thermostat comprising:

one or more solid state switching components adapted and arranged to provide switching on an off each of the one or more HVAC functions; and

current sensing circuitry adapted and arranged to sense current passing through the one or more solid state switching components.

26. A thermostat according to claim 25 wherein the current sensing circuitry includes circuitry to measure a voltage differential across at least one of the solid state switching components.

27. A thermostat according to claim 25 wherein the current sensing circuitry includes measuring a voltage differential across a thermistor in series with at least one of the solid state switching components.

28. A thermostat according to claim 25 wherein the current sensing is used at least in part for detection of a fault condition.

29. A thermostat according to claim 28 wherein the fault condition includes one or more wire connection faults.

30. A thermostat for controlling an HVAC system having multiple HVAC functions including a first HVAC function and a second HVAC function, the thermostat comprising circuitry housed within the thermostat adapted and configured to silently and automatically switch between the controlling the first and second HVAC functions, and to silently control the first HVAC function and the second HVAC function.

31. A thermostat according to claim 30 wherein the HVAC system is a residential or a light commercial HVAC system.

32. A thermostat according to claim 30 wherein the first HVAC function is cooling and has a cooling capacity of less than about 5 tons.

33. A thermostat according to claim 32 wherein the second HVAC function is heating.

34. A thermostat according to claim 30 wherein the HVAC system has a third HVAC function and the circuitry is further adapted and configured to silently and automatically switch between the controlling the first, second and third HVAC functions, and to silently control the third HVAC function.

35. A thermostat according to claim 34 wherein the first HVAC function is heating, the second HVAC function is cooling and the third HVAC function is ventilation.

36. A thermostat according to claim 30 wherein the circuitry is relayless and is solid-state.

37. A method for controlling an HVAC system having multiple HVAC functions including a first HVAC function and a second HVAC function, the method comprising:

silently and automatically controlling the first HVAC function;

silently and automatically switching from controlling the first HVAC functions to controlling the second HVAC function; and

silently and automatically controlling the second HVAC function.

38. A thermostat according to claim 37 wherein the first HVAC function is cooling and has a cooling capacity of less than about 5 tons.