CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the benefit of U.S. Prov. Ser. No. 61/415,771 filed Nov. 19, 2010; and of U.S. Prov. Ser. No. 61/429,093 filed Dec. 31, 2010. The subject matter of this patent application also relates to the subject matter of the following commonly assigned applications: U.S. Ser. No. 12/881,430 filed Sep. 14, 2010; U.S. Ser. No. 12/881,463 filed Sep. 14, 2010; U.S. Ser. No. 12/984,602 filed Jan. 4, 2011; U.S. Ser. No. 12/987,257 filed Jan. 10, 2011; U.S. Ser. No. 13/034,674, entitled “Thermostat Circuitry for Connection to HVAC Systems,” filed Feb. 24, 2011; and U.S. Ser. No. 13/034,678, entitled “Thermostat Battery Recharging During HVAC Function Active and Inactive States,” filed Feb. 24, 2011. Each of the above-referenced patent applications is incorporated by reference herein. 
    
    
     COPYRIGHT AUTHORIZATION 
     A portion of the disclosure of this patent document may contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND 
     This invention generally relates to control systems for heating, ventilation and air conditioning (HVAC) systems. More particularly, embodiments of this invention relate to wiring connectors for use in HVAC system thermostats. 
     As is known, for example as discussed in the technical publication No. 50-8433, entitled “Power Stealing Thermostats” from Honeywell (1997), early thermostats used a bimetallic strip to sense temperature and respond to temperature changes in the room. The movement of the bimetallic strip was used to directly open and close an electrical circuit. Power was delivered to an electromechanical actuator, usually relay or contactor in the HVAC equipment whenever the contact was closed to provide heating and/or cooling to the controlled space. Since these thermostats did not require electrical power to operate, the wiring connections were very simple. Only one wire connected to the transformer and another wire connected to the load. Typically, a 24 VAC power supply transformer, the thermostat, and 24 VAC HVAC equipment relay were all connected in a loop with each device having only two external connections required. 
     When electronics began to be used in thermostats the fact that the thermostat was not directly wired to both sides of the transformer for its power source created a problem. This meant either the thermostat had to have its own independent power source, such as a battery, or be hardwired directly from the system transformer. Direct hardwiring a “common” wire from the transformer to the electronic thermostat may be very difficult and costly. However, there are also disadvantages to using a battery for providing the operating power. One primary disadvantage is the need to continually check and replace the battery. If the battery is not properly replaced and cannot provide adequate power, the electronic thermostat may fail during a period of extreme environmental conditions. 
     Since many households did not have a direct wire from the system transformer (such as a “Common” wire), some thermostats have been designed to derive power from the transformer through the equipment load. The methods for powering an electronic thermostat from the transformer with a single direct wire connection to the transformer is called “power stealing” or “power sharing.” The thermostat “steals,” “shares” or “harvests” its power during the “OFF” periods of the heating or cooling system by allowing a small amount of current to flow through it into the load coil below its response threshold (even at maximum transformer output voltage). During the “ON” periods of the heating or cooling system the thermostat draws power by allowing a small voltage drop across itself. Hopefully, the voltage drop will not cause the load coil to dropout below its response threshold (even at minimum transformer output voltage). Examples of thermostats with power stealing capability include the Honeywell T8600, Honeywell T8400C, and the Emerson Model 1F97-0671. However, these systems do not have power storage means and therefore always rely on power stealing or must use disposable batteries. 
     SUMMARY 
     According to some embodiments a thermostat is provided for controlling HVAC systems. The thermostat includes one or more wiring terminals each adapted and configured to make an electrical connection with an HVAC system conductive wire. The making of the connection with the HVAC system wire actuates switching in a loop of an electrical circuit that does not include the HVAC system conductive wire. According to some embodiments, making the connection with the HVAC wire switches open the loop, and the loop is used for power harvesting. For example the loop can include an HVAC wire for a controlling part of a cooling system and/or part of a heating system, and the wire connected to the terminal can be a common wire. According to some embodiments the making of the connection is used to electronically sense the presence of the HVAC wire. According to some embodiments, the making of the connection is used to automatically isolate Rc and Rh wires from each other when both are present. According to some embodiments, the wiring terminal includes actuation of a moveable part of the terminal so as to accommodate the HVAC system wire that in turn actuates the switching of the loop. According to some embodiments the wiring terminal actuates switching in more than one other loops. According to some embodiments the thermostat is primarily designed for controlling residential, and/or light commercial HVAC systems. According to some embodiments, the HVAC system has a cooling capacity of less than about five tones. 
     According to some embodiments a method of installing a thermostat in an HVAC system is provided. The method includes connecting an HVAC system conductive wire to a terminal in the thermostat; and, in response to the connecting, automatically actuating switching in a loop of an electrical circuit that does not include the HVAC system conductive wire. 
     According to some embodiments, a thermostat for controlling an HVAC system is provided that includes a wiring terminal adapted and configured to make an electrical connection with an HVAC system conductive wire, wherein connecting the HVAC system wire causes switching open of a loop of an electrical circuit used for power harvesting. 
     According to some embodiments, a wiring terminal for connecting to a conductive wire is provided. The terminal includes an opening to accept the conductor by actuating a moveable portion of the terminal so as to accommodate the conductive wire, wherein the actuating of the moveable portion actuates switching a loop of an electrical circuit that does not include the conductive wire. 
     As used herein the terms power “harvesting,” “sharing” and “stealing” when referring to HVAC thermostats all refer to the thermostat are designed to derive power from the power transformer through the equipment load without using a direct or common wire source directly from the transformer. 
     As used herein the term “HVAC” includes systems providing both heating and cooling, heating only, cooling only, as well as systems that provide other occupant comfort and/or conditioning functionality such as humidification, dehumidification and ventilation. 
     As used herein the term “residential” when referring to an HVAC system means a type of HVAC system that is suitable to heat, cool and/or otherwise condition the interior of a building that is primarily used as a single family dwelling. An example of a cooling system that would be considered residential would have a cooling capacity of less than about 5 tons of refrigeration (1 ton of refrigeration=12,000 Btu/h). 
     As used herein the term “light commercial” when referring to an HVAC system means a type of HVAC system that is suitable to heat, cool and/or otherwise condition the interior of a building that is primarily used for commercial purposes, but is of a size and construction that a residential HVAC system is considered suitable. An example of a cooling system that would be considered residential would have a cooling capacity of less than about 5 tons of refrigeration. 
     As used herein the term “common wire” when referring to HVAC systems refers to a direct wire from an HVAC power transformer that is in addition to the power or return wire to the transformer. Thus, power can be drawn from a circuit including the common wire and the power or return wire without risk of switching on or off relays, switches and/or contactors for operating various HVAC systems since those switching means are not in series in such a circuit. 
     As used herein the term “silent” or “silently” when referring to thermostat operation and/or control means that any sound made by the thermostat is generally inaudible to the human ear at a range of greater than 1 meter. 
     It will be appreciated that these systems and methods are novel, as are applications thereof and many of the components, systems, methods and algorithms employed and included therein. It should be appreciated that embodiments of the presently described inventive body of work can be implemented in numerous ways, including as processes, apparata, systems, devices, methods, computer readable media, computational algorithms, embedded or distributed software and/or as a combination thereof. Several illustrative embodiments are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The inventive body of work will be readily understood by referring to the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram of an enclosure for which thermodynamic behavior is predicted, according to some embodiments; 
         FIG. 2  is a diagram of an HVAC system, according to some embodiments; 
         FIGS. 3A and 3B  are schematic diagrams of a thermostat installed in an HVAC system not having an available common wire, and in an HVAC system having an available common wire, respectively, according to some embodiments; 
         FIGS. 4A, 4B and 4C  show a thermostat connector with automatic switching of independent circuits, according to some embodiments; 
         FIG. 5  shows a terminal block used for an HVAC thermostat, according to some embodiments; 
         FIGS. 6A-B  show a thermostat connector with automatic switching of independent circuits, according to some embodiments; 
         FIGS. 7A-B  show an HVAC thermostat  700  having a backplate and a head unit, according to some embodiments; 
         FIGS. 7C-D  illustrate further detail for terminal blocks, according to some embodiments; 
         FIG. 8  is a schematic showing wiring for automatic jumpering for Rc and Rc terminals, according to some embodiments; and 
         FIGS. 9A-C  schematically illustrate the use of connectors being used to automatically select a source for power harvesting, according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of the inventive body of work is provided below. While several embodiments are described, it should be understood that the inventive body of work is not limited to any one embodiment, but instead encompasses numerous alternatives, modifications, and equivalents. In addition, while numerous specific details are set forth in the following description in order to provide a thorough understanding of the inventive body of work, some embodiments can be practiced without some or all of these details. Moreover, for the purpose of clarity, certain technical material that is known in the related art has not been described in detail in order to avoid unnecessarily obscuring the inventive body of work. 
       FIG. 1  is a diagram of an enclosure for which thermodynamic behavior is predicted, according to some embodiments. Enclosure  100 , in this example is a single-family dwelling According to other embodiments, the enclosure can be, for example, a duplex, an apartment within an apartment building, a light commercial structure such as an office or retail store, or a structure or enclosure that is a combination of the above. Thermostat  110  controls HVAC system  120  as will be described in further detail below. According to some embodiments, the HVAC system  120  is has a cooling capacity less than about 5 tons. 
       FIG. 2  is a diagram of an HVAC system, according to some embodiments. HVAC system  120  provides heating, cooling, ventilation, and/or air handling for the enclosure, such as a single-family home  100  depicted in  FIG. 1 . The system  120  depicts a forced air type heating system, although according to other embodiments, other types of systems could be used such as hydronic, in-floor radiant heating, heat pump, etc. In heating, heating coils or elements  242  within air handler  240  provide a source of heat using electricity or gas via line  236 . Cool air is drawn from the enclosure via return air duct  246  through fan  238  and is heated heating coils or elements  242 . The heated air flows back into the enclosure at one or more locations via supply air duct system  252  and supply air grills such as grill  250 . In cooling an outside compressor  230  passes gas such as Freon through a set of heat exchanger coils to cool the gas. The gas then goes to the cooling coils  234  in the air handlers  240  where it expands, cools and cools the air being circulated through the enclosure via fan  238 . According to some embodiments a humidifier  254  is also provided. Thermostat  110  also includes a processing system  264  such as a microprocessor that is adapted and programmed to controlling the HVAC system and to carry out the techniques described in detail herein. Although not shown in  FIG. 2 , according to some embodiments the HVAC system has other known functionality such as venting air to and from the outside, and one or more dampers to control airflow within the duct systems. 
     Thermostat  110  controls the HVAC system  120  through a number of control circuits. In particular, there are often separate control systems for heating and cooling. The heating system can include a low voltage, for example 24 VAC, operated gas valve which controls the flow of gas to the furnace; the cooling system includes a contactor having a low-voltage coil and high-voltage contacts which control energizing of the compressor; and the circulation system includes a fan relay having a low-voltage coil and high-voltage contacts which control energizing of the fan which circulates the conditioned air. The electrical power for energizing such low-voltage operated devices is provided either by a single transformer  260  for both heating and cooling, or by two separate transformers  260  for heating and  262  for cooling. Often, a single transformer is provided when the heating and cooling system is installed as a complete unit. If the cooling system is added to an existing heating system, sometimes an additional transformer is used. 
     An electronic programmable thermostat that requires power from the HVAC system is provided. The thermostat is flexible in that it can be installed in buildings having different types of HVAC systems. In particular, the thermostat can be wired directly to an HVAC system having a common wire, so that the thermostat can draw power directly from the power transformer, it can be wired to an HVAC system which does not have a common wire, so the thermostat can draw power using power harvesting circuitry from the HVAC system control loops. In order to have a single thermostat that can be connected to either type of HVAC system (i.e. with our without a common wire), the thermostat must detect which power sources are present and then draw power from the best available power source. 
       FIGS. 3A and 3B  are schematic diagrams of a thermostat installed in an HVAC system not having an available common wire, and in an HVAC system having an available common wire, respectively, according to some embodiments.  FIG. 3A  shows a thermostat  310  wired for control to an HVAC system having two power transformers  360  and  362  and no common wire available to the thermostat. A two-transformer HVAC system is commonly found in residences and light commercial building in which an existing heating system was subsequently upgraded or had had an air conditioning system installed. Heat power transformer  360  converts 110 volt AC power to 24 volt AC power for the heating control circuit  364 . Similarly, cooling power transformer  362  converts 110 volt AC power to 24 volt AC power for the cooling control circuit  366 . Note that the 110 or 24 volt levels could be different, depending on the location of the building and/or what types of power is available. For example, the 110 volts could be 220 or 240 volts in some geographic locations. 
     Relay  370  controls the gas valve for the HVAC heating system. When sufficient AC current flows through the gas valve relay  370 , gas in the heating system is activated. The gas valve relay  370  connected via a wire to terminal  334 , which is labeled the “W” terminal, on thermostat  310 . Relay  372  controls the fan for the HVAC heating and cooling systems. When sufficient AC current flows through the fan relay  372 , the fan is activated. The fan relay  372  connected via a wire to terminal  340 , which is labeled the “G” terminal on thermostat  310 . Contactor (or relay)  374  controls the compressor for the HVAC cooling system. When sufficient AC current flows through the compressor contactor  374 , the compressor is activated. The contactor  374  connected via a wire to terminal  330 , which is labeled the “Y” terminal, on thermostat  310 . The heat power transformer  360  is connected to thermostat  310  via a wire to terminal  336 , which is labeled the “Rh” terminal. The cooling power transformer  362  is connected to thermostat  310  via a wire to terminal  332 , which is labeled the “Rc” terminal. Note that unlike the HVAC system shown in  FIG. 3B , the system shown in  FIG. 3A  has no common wire available to the thermostat  310 . 
     Thermostat  310  has a number of components that are not shown. For further details of components of thermostat  310 , according to some embodiments, see co-pending U.S. patent application Ser. No. 13/034,674 entitled “Thermostat Circuitry for Connection to HVAC Systems,” and Ser. No. 13/034,678 entitled “Thermostat Battery Recharging During HVAC Function Active and Inactive States,” filed Feb. 24, 2011, both of which are incorporated herein by reference. Thermostat  310  has power harvesting circuitry  320 , including circuitry  322 ,  324  and  326  for harvesting power from the cooling control circuit  666 , heating control circuit  364  and a common wire, which is not available in the HVAC system shown in  FIG. 3A . Switches  350 ,  352 ,  354  and  356  are used to open and close the connection between the power harvesting circuitry  320  and the “Y” terminal  330 , “Rc” terminal  332 , “W” terminal  334  and “Rh” terminal  336  respectively. When there is not common wire connected to thermostat  310 , as shown in  FIG. 3A , the switches  350 ,  352 ,  354  and  356  are closed as shown, such that power harvesting circuitry  322  and  324  can operate to harvest power from the cooling control circuit  366  and from the heating control circuit  364 . 
       FIG. 3B  shows a thermostat  310  wired for control to an HVAC system having two power transformers  360  and  362 , as shown in  FIG. 3A , except that in this case a common wire  368  is available. The common wire  368  directly connects the HVAC heating transformer  360  and terminal  338  of thermostat  310 . Since a common wire  368  is present, the thermostat  310  can draw power, via power harvesting circuitry  326  directly from the heating transformer  360  without any of the HVAC relays  370 ,  372 , and  374  in the loop. Thus, drawing power from the common wire  368  is the preferred power source for thermostat  310 . Accordingly, the switches  350 ,  352 ,  354  and  356  are opened such that power harvesting using circuitry  322  and  324  does not take place. According to some embodiments, as will be described more fully below, terminal connector  338  is adapted to automatically open the switches  350 ,  352 ,  354  and  356  upon connection of a common wire. 
     Note that although the HVAC systems shown in  FIGS. 3A and 3B  have two power transformers  360  and  362 , the thermostat  310  can be used with HVAC systems having only a single power transformer. Further, the thermostat  310  can be used with an HVAC system having only a single HVAC function, such as only heating or only cooling. Further the thermostat  310  can be used with HVAC systems have more complex functionality such as multiple heating and/or cooling stages, and/or humidification and/or dehumidification. 
       FIGS. 4A, 4B and 4C  show a thermostat connector with automatic switching of independent circuits, according to some embodiments.  FIG. 4A  is a side view of the connector  400 . The connector  400  has a body  402  that has a conical opening  404  and a cylindrical opening  406  which accepts an HVAC wire conductor (not shown). The connector  400  includes a push button  410  to actuate a first primary conductor  430 . The first primary conductor  430  is made of metal is shaped so as to be stable in the position shown in  FIG. 4A . The conductor  430  can be electrically connected to a circuit board via pin  434 . The conductor  430  includes a window  432  that is shaped and dimensioned to accept an HVAC wire conductor when the window  432  is positioned so as to be aligned with the cylindrical opening  406 . The window  432  can be translated down by applying downward force on the button  410  which deforms conductor  430  which pivots on fulcrum member  450 . The conductor  430  has a spring force that tends to resist the downward force on button  410  to return the button  410  and the conductor  430  to return to the position shown in  FIG. 4A . A second primary conductor  440  is fixedly mounted within the connector  400  and can be electrically connected to a circuit board using pins  442  and or  444 . The conductor  440  is “C” shaped and has an upper flat angled portion  446  that will accept and make electrical contact with an HVAC wire conductor. 
     The connector  400  also includes one or more pairs of secondary conductors such as secondary conductor  460  and  462 . The two conductors within each secondary conductor pair are in contact with one another when the there is no HVAC wire conductor inserted in connector  400 , such as shown in the  FIG. 4A . In  FIG. 4A , the rear lever portion  412  of button  410  pushed on a portion of conductor  462  so as to be in electrical contact with conductor  460 . The secondary conductors  460  and  462  are connected to a circuit board via the lower pin portions of each conductor. Thus, when an HVAC wire conductor is not inserted in the connector  400 , as shown in  FIG. 4A , the spring force of primary conductor  430  maintains pressure on button  410  which maintains contact between conductors  460  and  462  via lever portion  412 . 
       FIG. 4B  shows a side view of the connector  400  with an HVAC wire conductor  420  inserted, according to some embodiments. The HVAC wire conductor  420  has an insulated portion  422  that is striped away so as to expose a sufficient amount of conductor  420  for secure insertion and connection with connector  400 . The wire conductor  420  is inserted as shown through the cylindrical opening of body  402  and through the window portion  432  of first primary conductor  430 . The HVAC wire conductor  420  is also held in place by contacting the upper flat portion  446  of the second primary conductor  440 . The spring force from the deformation of conductor  430  acts to urge the wire  420  into contact with both the lower portion of the window of conductor  430  and the lower surface of the upper flat portion  446  of conductor  440 . The wire  420  is thus maintained securely in connector  400  and in electrical contact with both conductor  430  and conductor  440 . 
     When an HVAC wire conductor is inserted in connector  400 , as shown in  FIG. 4B , the lever portion  412  of button  410  is positioned as shown such that the secondary conductors  460  and  462  are not in contact with one another. In particular, the conductor  462  is shaped such that it exerts a spring force towards the lever portion  412  and away from the upper portion of conductor  460 . Thus, when the HVAC wire conductor is inserted in the connector  400  the contact between conductor  460  and conductor  462  is broken. 
       FIG. 4C  is a perspective view of connector  400 . Note that the position of button  410  and conductor  430  are shown as if an HVAC wire conductor is not inserted, although a wire conductor  420  is shown in broken lines for positional reference. For example, note that the window  432  of conductor  430  is not aligned with the conductor  420 . Note that in  FIG. 4C  there are four pairs of secondary conductors, that are in a closed stated when a wire conductor is not inserted and in an open state when a wire is inserted. In  FIG. 4C , secondary pairs  460 - 462 ,  470 - 472  and  480 - 482  are shown. The connector  400  thus acts to automatically actuate switches formed by each secondary conductor pair when an HVAC wire conductor is inserted. According to some embodiments, other numbers of pairs of secondary conductors are used with one or more connectors in the thermostat. For example, some connectors can have a single pair of secondary conductors, other connectors can have two pairs of secondary conductors, and yet other connectors can have three pairs, depending on the electrical design of the thermostat. 
     According to some embodiments, the connector  400  shown in  FIGS. 4A, 4B and 4C  is used in a thermostat to accept and make connection with a common wire, if available from the HVAC system where the thermostat is being installed. Power harvesting circuitry is connected to the four secondary conductor pairs, which is activated or used when there is no common wire inserted, and deactivated or not used when a common wire is inserted. In particular, according to some embodiments, the four secondary conductor pairs corresponds to the switches  350 ,  352 ,  354  and  356  as shown and described with respect to  FIGS. 3A and 3B , and the connector  400  corresponds to the terminal  338  as shown and described with respect to  FIGS. 3A and 3B . 
       FIG. 5  shows a terminal block used for an HVAC thermostat, according to some embodiments. Terminal block  500  is shown and includes terminals or connectors for accepting and making contact between the thermostat and up to 6 HVAC wire conductors. Connector  400  is shown with a button  410  and accepts an HVAC common wire  420 , if available. The connector  410  also includes four automatically switched pairs of conductors of which conductors  462 ,  472 ,  482  and  492  are shown, although according to some embodiments, other numbers of pairs can be provided. Connectors  510 ,  512 ,  514 ,  516  and  518  are also part of terminal block  500 , and accepts HVAC wires  520  (Rc),  522  (Rh),  524  (Y),  526  (W) and  528  (G), respectively, if available. The connectors  510 ,  512 ,  514 ,  516  and  518  also have buttons  530 ,  532 ,  534 ,  536  and  538 , respectively and operate as shown in  FIGS. 4A, 4B and 4C , except that no secondary switched pairs of conductors are included. 
       FIGS. 6A-B  show a thermostat connector with automatic switching of independent circuits, according to some embodiments.  FIG. 6A  is a perspective view of the connector  600 . The connector  600  has a body  602  that has a conical opening  604  and a cylindrical opening  606  which accepts an HVAC wire conductor (not shown). The connector  600  includes a push button  610  having a rounded depression  614 . When button  610  is depressed the button pivots about axis  608 , the opening  604  aligns with cylindrical opening  606  such that an HVAC wire can be accepted, and a lever (shown in  FIG. 6B ) disconnects electrical contact between secondary conductors  660  and  662 . 
       FIG. 6B  is a cut-away perspective view of connector  600 . When button  610  is depressed the button pivots about an axis  608  (shown in  FIG. 6A ) and three actions take place. First the lever  612  moves rearward and electrical contact between three pairs of secondary conductors are opened such as pair of secondary conductors  660  and  662 . Second, the button  610  pushes downward on a first primary conductor  630  and bends conductor  630  such that window  632  is aligned with the cylindrical opening  606 . Third, the opening  604  aligns with cylindrical opening  606  such that an HVAC wire can be accepted through opening  606 , window  632 , and make contact with the upper surface  646  of a second primary conductor  640 . Note that although three pairs of secondary conductors are shown in  FIG. 6B , according to some embodiments other connectors on the same thermostat have other numbers of pairs of secondary conductors. According to some embodiments, some connectors have a single pair of secondary conductors and other connectors have two pairs of secondary conductors. Further, according to some embodiments, high current and/or high voltage capacity pairs of conductors can be provided by using wider and/or thicker conductors and contact areas. Finally, the pairs of secondary conductors shown are normally-closed, in that the conductors electrically contact each other unless the button  614  is actuated and a wire is inserted in the connector. However according to some embodiments, one or more of the pairs of secondary conductors can be normally open, such that the two secondary conductors do not electrically contact each other unless the button  614  is actuated and a wire is inserted. 
     The first primary conductor  630  is made of metal is shaped so as to be stable in the position shown in  FIGS. 6A-B . The conductor  630  can be electrically connected to a circuit board via pin  634 . The window  632  can thus be translated down by applying downward force on the button  610  which deforms conductor  630  which pivots on fulcrum member  650 . The conductor  630  has a spring force that tends to resist the downward force on button  610  to return the button  610  and the conductor  630  to return to the position shown in  FIGS. 6A-B . A second primary conductor  640  is fixedly mounted within the connector  600  and can be electrically connected to a circuit board using pin  644 . The conductor  640  is “C” shaped and has an upper flat angled portion  646  that will accept and make electrical contact with an HVAC wire conductor. The conductor  640  also has a tongue member  642  that protrudes through the window  632  as shown. The design shown in  FIGS. 6A-B  has advantages over the design shown in  FIGS. 4A-C . Firstly, the cylindrical opening  606  is only aligned with opening  604  when the button  610  is sufficiently depressed. This helps to ensure that electrical contact between the secondary pairs of conductors is open before electrical contact is made between the HVAC wire and either of the primary conductors  630  and  640 . Secondly, the tongue member  642  helps to ensure that the conductor  630  is maintained in position and that the HVAC wire is guided into the proper position. 
     As in the case of connector  400  of  FIGS. 4A-C , two secondary conductors are associated with each secondary conductor pair and are in electrical contact with one another when the there is no HVAC wire conductor inserted in connector  600 . The secondary conductors  660  and  662  are connected to a circuit board via the lower pin portions of each conductor. Thus, when an HVAC wire conductor is not inserted in the connector  600 , the spring force of primary conductor  630  maintains pressure on button  610  which maintains contact between conductors  660  and  662  via lever portion  612 . 
     When an HVAC wire (not shown) is inserted, it passes through the conical opening  604 , cylindrical opening  606 , and through the window portion  632  of first primary conductor  630 . The HVAC wire conductor is also held in place by contacting the upper flat portion  646  of the second primary conductor  640 . The spring force from the deformation of conductor  630  acts to urge the HVAC wire into contact with both the lower portion of the window  632  of conductor  630  and the lower surface of the upper flat portion  646  of conductor  640 . The HVAC wire is thus maintained securely in connector  600  and in electrical contact with both conductor  630  and conductor  640 . Additionally, when an HVAC wire conductor is inserted in connector  600  the lever portion  612  of button  610  is positioned as shown such that the secondary conductors  660  and  662  are not in contact with one another. In particular, the conductor  662  is shaped such that it exerts a spring force towards the lever portion  612  and away from the upper portion of conductor  660 . Thus, when the HVAC wire conductor is inserted in the connector  600  the contact between conductor  660  and conductor  662  is broken. The same action takes place in the other two pairs of secondary conductors such that the electrical connection in all three pairs of secondary conductors is broken by the pressing of button  610 . The connector  600  thus acts to automatically actuate switches formed by each secondary conductor pair when an HVAC wire conductor is inserted. 
     Note that the primary conductors  630  and  640  are not normally in electrical contact with each other when there is no wire inserted, and when a wire is inserted, the two primary conductors  630  and  640  are electrically connected through the inserted wire. Thus, a normally-open switch is formed by the pair of primary conductors  630  and  640  which can be used for detection of electrical communication with an inserted wire, and/or high current applications, due to the relatively large contact surfaces on conductors  630  and  640 . 
     According to some embodiments, the connector  600  shown in  FIGS. 6A-B  is used in a thermostat to accept and make connection with a common wire, if available from the HVAC system where the thermostat is being installed. Power harvesting circuitry is connected to the three secondary conductor pairs, which is activated or used when there is no common wire inserted, and deactivated or not used when a common wire is inserted. In particular, according to some embodiments, the three secondary conductor pairs corresponds to the switches  350 ,  352 ,  354  and  356  as shown and described with respect to  FIGS. 3A and 3B , and the connector  600  corresponds to the terminal  338  as shown and described with respect to  FIGS. 3A and 3B . 
       FIGS. 7A-B  show and HVAC thermostat  700  having a backplate ( FIG. 7A ) and a head unit ( FIG. 7B ), according to some embodiments. In backplate  740 , two terminal blocks  772  and  774  are shown and include terminals or connectors for accepting and making contact between the thermostat and up to 8 HVAC wire conductors. According to some embodiments, connector  770  corresponds to connector  400  and connector  600  as shown in and described with respect to  FIGS. 4A-C  and  6 A-B respectively. Connector  770  has a button  776  and accepts an HVAC common wire, if available. The connector  770  also includes three automatically switched pairs of conductors as shown in and described with respect to  FIGS. 4A-C  and  6 A-B. The other connectors in blocks  772  and  774 , and accept other HVAC wires such as Y/Y 1 , W/W 1 , Aux, Rc, Rh, G and O/B, if available. The connectors have buttons and operate as shown in  FIGS. 4A-C  or  FIGS. 6A-B , and according to some embodiments, include one or more pairs of secondary switched conductors. In particular, according to some embodiments, all of the connectors have at least one switched pair of secondary conductors that can be used, for example for the mechanical detection of the presence of a wire. Rh and Rc have two switched pairs of secondary conductors, one for detecting the presence of an inserted wire, and the other switched pair is used to turn off the power stealing from the other R terminal. According to some embodiments, other numbers of connectors are used for making connections to other numbers of HVAC wire conductors. For example, according to some embodiments connectors are provided for connection to seven additional HVAC wires, namely: W 2  (second stage heating); Y 2  (second stage cooling); E (heat pumps/emergency heating); HUM 1  and HUM 2  (humidifier terminals  1  and  2 ); and DEHUM 1  and DEHUM 2  (dehumidifier terminals  1  and  2 ). 
     Backplate  740  also includes, according to some embodiments, a bubble level  762 , a connector block  780  for connection to the head unit, and a body  760  for housing electronics.  FIG. 7B  shows a front view of a head unit that has a large circular display  716 , which can display central numerals such as  720  and other information to a user. The front cover  714  covers the display and the surrounding area. A rotating ring  712  surrounds the cover  714  and rotates to accept user input to thermostat  700 . 
       FIGS. 7C-D  illustrate further detail for terminal blocks, according to some embodiments. The left terminal block  772  in  FIG. 7C  includes connectors  770 ,  778 ,  782  and  784  for the HVAC wires Rh, W, Y and G, respectively. Similarly, the right terminal block  774  in  FIG. 7D  includes connectors  786 ,  788 ,  790  and  792  for the HVAC wires C, O/B, Aux and Rc, respectively. Each of the connectors in  FIGS. 7C and 7D  include either one, two or three pairs of secondary conductors, as is described with respect to  FIGS. 6A-B . According to some embodiments, the connectors  778 ,  784 ,  788 ,  790  (for HVAC wires W, G, O/B and Aux, respectively) each have one pair of normally-closed secondary conductors which are used to detecting the presence of an HVAC wire connected to that terminal. For example, connector  778  has a single switched pair  752  used to detect the presence of an HVAC wire connected to the “W” terminal. According to some embodiments, connectors  770  and  792  (for Rh and Rc, respectively) each have two pairs of normally-closed switched pairs of conductors. Each of the connectors  770  and  792  has a larger switch ( 750  and  746 , respectively) designed to accept higher current loads such that it can be used to provide an automatic jumper functionality, as is described below with respect to  FIG. 8 . Each of the connectors  770  and  792  also has a smaller pair of normally-closed secondary conductors which are used to detecting the presence of an HVAC wire connected to that terminal. For example, connector  770  has a smaller switched pair  748 . According to some embodiments, connectors  782  and  786  (for Y and C, respectively) each have three switched pairs of secondary conductors, such as shown in  FIG. 6B . The C and Y terminals have additional switched pairs such that selections can be made to connect and/or disconnect power stealing circuitry, according to some embodiments. For example, the connector  782  has three switched pairs of secondary conductors  754 ,  756  and  758 . 
     Additionally, each connector shown in  FIGS. 7C and 7D  has a normally-open pair of conductors that make connection with the inserted HVAC wire, which correspond to primary conductors  630  and  640  in  FIG. 6B . The normally-open pair of conductors can be used for electrical detection of the wire. 
       FIG. 8  is a schematic showing wiring  810  for automatic jumpering for Rc and Rc terminals, according to some embodiments. Terminal  820  is the Rc terminal and corresponds to, for example, connector  792  in  FIG. 7D . A fuse  822  is included for protection of the circuit  810  and to other circuitry within the thermostat which is connected to terminal  824 . A normally closed high current switch  826  is provided that is opened upon sensing the presence of an Rc wire. The switch  826 , for example, corresponds to the switched secondary pair  746  in  FIG. 7D . Terminal  830  is the Rh terminal and corresponds to, for example, connector  770  in  FIG. 7C . A fuse  832  is included for protection of the circuit  810  and to other circuitry within the thermostat which is connected to terminal  834 . A normally closed high current switch  836  is provided that is opened upon sensing the presence of an Rh wire. The switch  836 , for example, corresponds to the switched secondary pair  750  in  FIG. 7C . Thus if either Rc or and Rh wire is connected to the thermostat, but not both, then one of the switches will remain closed and the thermostat can control the HVAC functions using the Rc or Rh wire. However, if both Rc and Rh wires are connected (such as the case with an HVAC system having two power transformers) then both switches  826  and  836  are opened and the two wires Rc and Rh are automatically electrically isolated from each other, advantageously avoiding the use of manual jumpers, and avoiding high voltages associated with having both Rc and Rh wires electrically connected. 
       FIGS. 9A-C  schematically illustrate the use of connectors being used to automatically select a source for power harvesting, according to some embodiments. The connectors  786 ,  783 , and  778  are connectors as shown in and described with respect to  FIGS. 7A, 7C and 7D . The connector  786  is used for connection to an HVAC “C” (common) wire and includes two switched pairs of normally closed secondary conductors  910  and  912 . The connector  782  is used for connection to an HVAC “Y” (cooling) wire and includes one switched pair of normally closed secondary conductors  754 . The connector  778  is used for connection to an HVAC “W” (heating) wire. Note that although not shown in  FIGS. 9A-C , one or more additional pairs of switched secondary conductors can be provided with any of the connectors  786 ,  783  and  778 , such as could be used for the purpose of electronically detecting the presence of an HVAC system wire to the connector. Power harvesting circuitry  920  is used to supply power to the thermostat and is also connected to the Rc wire  824  (or according to other embodiment the Rh wire). 
       FIG. 9A  shows the case of the switches  754 ,  910  and  912  when no C wire and no Y wire is attached. In this case all of the switches  754 ,  910  and  912  are closed and the power harvesting circuitry  920  is connected with the W wire via circuit paths  920 ,  922  and  926 .  FIG. 9B  shows the case of the switches  754 ,  910  and  912  when no C wire is attached but there is a Y wire attached. In this case switches  910  and  912  are closed but switch  754  is opened due to the presence of the Y wire. In this case the power harvesting circuitry  920  is connected with the Y wire via circuit paths  924  and  928 .  FIG. 9C  shows the case of the switches  754 ,  910  and  912  when both C and Y wires are attached. In this case all the switches  754 ,  910  and  912  are open and the power harvesting circuitry  920  is connected with the C wire via circuit path  930 . Note that the case of a connection of C and W wires and no Y wire is not shown but that in this case the W wire would not be connected to circuitry  920  since switch  910  would be open. Thus, through the use of circuitry and the connectors shown, the power harvesting circuitry is automatically switch so as to use connections to C, Y and W wires in decreasing order of priority. Preferably, the C wire is the highest priority as this ordinarily provides the best power source, if available. Note that according to some embodiments, the Y and W priorities are reversed to make W higher priority than Y. 
     Although the foregoing has been described in some detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the inventive body of work is not to be limited to the details given herein, which may be modified within the scope and equivalents of the appended claims.
A thermostat includes a wiring terminal having a moveable component that is actuatable to enable insertion of an HVAC system conductive wire within the wiring terminal. Insertion of the HVAC system conductive wire within the wiring terminal electrically connects the wiring terminal and the HVAC system conductive wire. The actuation of the moveable component opens a loop of an electrical circuit that does not include the HVAC system conductive wire. The loop may enable power harvesting for the thermostat.