Two wire line voltage thermostat

• US 4,776,514 A
• Filed: 08/07/1987
• Issued: 10/11/1988
• Est. Priority Date: 11/17/1986
• Status: Expired due to Term

• Current Assignee: Honeywell Limited (Honeywell International Inc.)
• Original Assignee: Honeywell Limited (Honeywell International Inc.)
• Inventors: McDonnell, Brian E., Johnstone, Robert V.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US07/082,759
• Time in Patent Office: 431 Days
• Field of Search: 165/26, 236/46 R, 236/78 R, 307/310, 219/510, 219/514, 361/154, 361/155
• US Class Current: 236/78.00R
• CPC Class Codes: G05D 23/1927 using a plurality of sensors G05D23/1902, G05D23/1917, and G05D23/1919 take precedence
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

A two wire line voltage thermostat has first and second terminals for receiving line voltage power and for connection to a load, a transformer having a current primary winding, a voltage primary winding and a secondary winding, a primary controller connecting the current and voltage primary windings to the terminals, the controller having at least first and second states, the controller in the first state energizing both the current and voltage primary windings and in the second state energizing only the current primary winding, and a temperature responsive circuit connected to the secondary winding for controlling the controller between the first and second states in accordance with sensed temperature such that the load can be energized when the controller is in one of the states and can be deenergized when the controller is in the other of the states.

Claims

1. A two wire line voltage thermostat comprising

first and second terminals for receiving line voltage power and for connection to a load;

transformer means having current primary means, voltage primary means and secondary means;

primary control means connecting said current and voltage primary means to said terminals, said primary control means having at leasst first and second states, said primary control means in said first state energizing both said current and voltage primary means and in said second state energizing only said current primary means; and

temperature responsive means connected to said secondary means for controlling said primary control means between said first and second states in accordance with sensed temperature such that said load can be energized when said primary control means is in one of said states and can be deenergized when said primary control means is in one other one of said states, wherein said primary control means comprises a relay having a relay winding and relay contact means, said relay winding being energized and deenergized by said temperature response means, said relay contact means is response to said relay winding for energizing both said current and voltage primary means when said thermostat is in an off condition and for energizing only said current primary means when said thermostat is in an on condition, said primary control means further comprising an arc suppressing switch connected across said relay contact means for suppressing arcing of said relay contact means, and wherein said temperature responsive means comprises voltage regulation means connected to said secondary means for supplying regulated voltage and wherein temperature responsive means comprises a bridge circuit connected to the output of said regulation means and having a first thermistor responsive to ambient temperature and a second thermistor for compensating said bridge in response to heat generated by said thermostat.

2. The thermostat of claim 1 wherein said temperature responsive means comprises a comparator means connected to said bridge providing a first output usable in driving said primary control means to said first state in one condition of said bridge and a second output usable in driving said primary control means to said second state in response to a second condition of said bridge.

3. The thermostat of claim 2 wherein said temperature responsive means comprises time delay means connected to said comparator means for preventing operation of said relay at a rate above a predetermined amount.

4. The thermostat of claim 3 wherein said temperature responsive means comprises capacitive means responsive to said time delay means, said capacitive means comprising a capacitor for storing energy when said thermostat is off and for discharging through said relay winding when said thermostat is to switch from its off state to its on state, said relay winding receiving a lower hold-in current after discharge of said capacitor for reducing power dissipation in said relay winding.

5. The thermostat of claim 4 wherein said temperature responsive means comprises a triac gating circuit connected to said time delay means for gating on said arc suppression switch during transferring of said relay contacts.

6. The thermostat of claim 1 wherein said temperature responsive means comprises a bridge circuit connected by means to said secondary means and having a first thermistor responsive to ambient temperature and a second thermistor for compensating said bridge in response to heat generated by said thermostat.

7. The thermostat of claim 6 wherein said primary control means comprises a relay having a relay winding and a relay contact means, said relay winding being energized and deenergized by said temperature responsive means, said relay contact means in response to said relay windings for energizing both said current and voltage primary means when said thermostat is in an off condition and for energizing only said current primary means when said thermostat is in an on condition, said primary control means further comprising an arc suppressing switch connected across said relay contact means for suppressing arcing of said relay contact means.

8. The thermostat of claim 7 wherein said temperature responsive means comprises capacitive means responsive to said bridge circuit, said capacitive means comprising a capacitor for storing energy when said thermostat is off and for discharging through said relay winding when said thermostat is to switch from its off state to its on state, said relay winding re ceiving a lower hold in current after discharge of said capacitor for reducing power dissipation in said relay winding.

9. A two wire line voltage comprising

first and second terminals for receiving line voltage power and for connection to a load;

first and second supply means for supplying circuit energizing power;

control means connecting said first and second supply means to said terminals, said control means having at least first and second states, said control means in said first state for energizing both said first and second supply means and in said second state for energizing only said first supply means; and

temperature responsive means connected to said first and second supply means for receiving power from said first and second supply me ans when said control means is in said first state and for receiving power from only said first supply means when said control means is in said second state, said temperature responsive means being connected to said control means for controlling said control means between said first and second states in accordance with sensed temperature such that said load can be energized when said control means is in one of said states and can be deenergized when said control means is in the other of said states and wherein said temperature responsive means comprises a bridge circuit connected by means to said first and second supply means and having a first thermistor responsive to ambient temperature and a second thermistor for compensating said bridge in response to heat generated by said thermostat.

10. The thermostate of claim 9 wherein said control means comprises a relay having a relay winding and relay contact means, said relay winding being energized and deenergized by said temperature responsive means, said relay contact means in response to said relay winding for energizing both said first and second supply means when said thermostat is in an off condition and for energizing only said first supply means when said thermostat is in an on condition, said control means further comprising an arc suppressing switch connected across said relay contact means for suppressing arcing of said relay contact means.

11. The thermostat of claim 10 wherein said temperature responsive means comprises capacitive means responsive to said bridge circuit, said capacitive means comprising a capacitor for storing energy when said thermostat is off and for discharging through said relay winding when said thermostat is to switch from it off state to its on state, said relay winding receiving a lower hold-in current after discharge of said capacitor for reducing power dissipation in said relay winding.

12. The thermostat of claim 9 wherein said control means comprises a relay having a relay winding and relay contact means, said relay winding being energized and deenergized by said temperature responsive means, said relay contact means in response to said relay winding for energizing both said first and second supply means when said thermostat is in an off condition and for energizing only said first supply means when said thermostat is in an on condition.

13. The thermostat of claim 12 wherein said temperature responsive means comprises capacitive means, said capacitive means comprising a capacitor for storing energy when said thermostat is off and for discharging through said relay winding when said thermostat is to switch from its off state to its on state, said relay winding receiving a lower hold in current after discharge of said capacitor for reducing power dissipation in said relay winding

14. A line voltage thermostat comprising

first and second temrinals for receiving line voltage power and for connection to a load;

load control means having at least a first state for controlling energization of said load and a second state for controlling deenergiziation of said load and

temperature responsive means connected to said terminals and to said load controls means for controlling said load control means between said first and second states in accordance with sensed temperature, said temperature responsive means supplying a pull-in voltage to said load control means to operate said load control means to one of said states and for supplying a lower hold-in voltage to said load control means to maintain said load control means in said one of said states whereby said load control means generates less heat, wherein said load control means comprises a relay having a relay winding and a relay contact means, said relay winding being energized and deenergized by said temperature responsive means, said relay contact means in response to said relay winding for energizing and deenergizing said load and wherein said temperature responsive means comprises a bridge circuit having a first thermistor responsive to ambient temperature and a second thermistor for compensating said bridge in response to heat generated by said thermostat.