Thermostat incorporating thin film carbon dioxide sensor and environmental control system

• US 6,398,118 B1
• Filed: 01/29/1999
• Issued: 06/04/2002
• Est. Priority Date: 01/29/1999
• Status: Expired due to Fees

• Current Assignee: Howard B Rosen, Steven D. Dushane
• Original Assignee: Howard B Rosen, Steven D. Dushane
• Inventors: Dushane, Steven D., Rosen, Howard B.
• Primary Examiner(s): WAYNER, WILLIAM E
• Application Number:
  US09/240,506
• Time in Patent Office: 1,222 Days
• Field of Search: 73/310.5, 236/49.3, 236/11, 454/256, 454/257, 454/258, 454/239, 454/342, 165/248, 165/249
• US Class Current: 236/49.3
• 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 11/62 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 11/76 by means responsive to temperature, e.g. bimetal springs
• CPC Class Codes: F24F 11/80 for controlling the temperature of the supplied air
• CPC Class Codes: F24F 2110/50 Air quality properties
• CPC Class Codes: F24F 2110/70 Carbon dioxide
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A system for monitoring and modifying the quality and temperature of air within a conditioned space includes a blower unit, a damper unit for selectively admitting outside air into the conditioned space, a temperature moderating unit and a control unit. The control unit includes a thermostat and conventional temperature control apparatus for selectively activating the temperature moderating unit to maintain the desired temperature in the conditioned space. The control unit also incorporates CO₂ concentration measuring and control apparatus which includes a small CO₂ sensor. The CO₂ sensor includes a cathode, an anode and a solid electrolyte disposed intermediate and electrically in contact with each of the cathode and the anode to effect a primary electrical cell. A heater and a heater thermostat serve to maintain the temperature of the cell at about 250° C. The cathode and anode materials and the chemical composition of the electrolyte are further selected such that the voltage generated across the heated cell varies in accordance with the CO₂ concentration. CO₂ concentration modifying apparatus is responsive to sensing a first predetermined CO₂ concentration for turning on the blower unit and to sensing a second, higher, predetermined CO₂ concentration for actuating the damper unit to admit outside air.

Claims

1. A system for monitoring and modifying the quality and temperature of air within a conditioned space which includes a blower unit, a temperature moderating unit and a control unit, said control unit comprising:

A) a thermostat including temperature set point establishment means and temperature control means for selectively activating said temperature moderating unit when the temperature of the conditioned space deviates by a predetermined amount from the established temperature set point; and

B) CO₂ concentration measuring and control apparatus for the conditioned space, said CO₂ concentration measuring and control apparatus comprising;

1) a CO₂ sensor comprising;

a) a cathode electrode disposed on a substrate and fabricated from a first metal;

b) an anode electrode disposed on the substrate spaced from said cathode electrode, said anode electrode being fabricated from a second metal, said first and second metals being selected to have different oxidation-reduction values;

c) a solid electrolyte disposed on the substrate intermediate and electrically in contact with each of said cathode electrode and said anode electrode such that said cathode electrode, said anode electrode and said solid electrolyte effect a primary electrical cell;

d) a heater disposed on the substrate;

e) a heater thermostat disposed on the substrate and connected to said heater and to a source of electrical energy so as to maintain said primary electrical cell within a predetermined temperature range;

f) said first metal, said second metal and the chemical composition of said electrolyte being further selected such that the voltage established between said cathode and said anode varies in accordance with the CO₂ concentration at said primary electrical cell when the temperature of said primary electrical cell is within said predetermined temperature range; and

2) CO₂ concentration modifying apparatus responsive to the measurement of at least a first voltage level between said cathode and said anode representing a first predetermined CO₂ concentration for turning on said blower unit.

2. The system of claim 1 in which said heater thermostat is set to maintain said electrical cell within the range of 225°

C. to 275°

C. and preferably at about 250°

C.

3. The system of claim 2 in which said first metal is platinum, said second metal is silver and said solid electrolyte is a mixture of Na₂CO₃, BaCO₃ and AG₂SO₄.

4. A system for monitoring and modifying the quality and temperature of air within a conditioned space which includes a damper unit for selectively admitting outside air into the conditioned space, a temperature moderating unit and a control unit, said control unit comprising:

A) a thermostat including temperature set point establishment means and temperature control means for selectively activating said temperature moderating unit when the temperature of the conditioned space deviates by a predetermined amount from the established temperature set point; and

B) CO₂ concentration measuring and control apparatus for the conditioned space, said CO₂ concentration measuring and control apparatus comprising;

1) a CO₂ sensor comprising;

a) a cathode electrode disposed on a substrate and fabricated from a first metal;

b) an anode electrode disposed on the substrate spaced from said cathode electrode, said anode electrode being fabricated from a second metal, said first and second metals being selected to have different oxidation-reduction values;

c) a solid electrolyte disposed on the substrate intermediate and electrically in contact with each of said cathode electrode and said anode electrode such that said cathode electrode, said anode electrode and said solid electrolyte effect a primary electrical cell;

d) a heater disposed on the substrate;

e) a heater thermostat disposed on the substrate and connected to said heater and to a source of electrical energy so as to maintain said primary electrical cell within a predetermined temperature range;

f) said first metal, said second metal and the chemical composition of said electrolyte being further selected such that the voltage established between said cathode and said anode varies in accordance with the CO₂ concentration at said primary electrical cell when the temperature of said primary electrical cell is within said predetermined temperature range; and

2) CO₂ concentration modifying apparatus responsive, to the measurement of at least a first voltage level between said cathode and said anode representing a first predetermined CO₂ concentration for actuating said damper unit to admit outside air into the conditioned space.

5. The system of claim 4 in which said heater thermostat is set to maintain said electrical cell within the range of 225°

C. to 275°

C. and preferably at about 250°

C.

6. The system of claim 5 in which said first metal is platinum, said second metal is silver and said solid electrolyte is a mixture of Na₂CO₃, BaCO₃ and AG₂SO₄.

7. A system for monitoring and modifying the quality and temperature of air within a conditioned space which includes a blower unit, a damper unit for selectively admitting outside air into the conditioned space, a temperature moderating unit and a control unit, said control unit comprising:

A) a thermostat including temperature set point establishment means and temperature control means for selectively activating said temperature moderating unit when the temperature of the conditioned space deviates by a predetermined amount from the established temperature set point; and

B) CO₂ concentration measuring and control apparatus for the conditioned space, said CO₂ concentration measuring and control apparatus comprising;

1) a CO₂ sensor comprising;

a) a cathode electrode disposed on a substrate and fabricated from a first metal;

b) an anode electrode disposed on the substrate spaced from said cathode electrode, said anode electrode being fabricated from a second metal, said first and second metals being selected to have different oxidation-reduction values;

c) a solid electrolyte disposed on the substrate intermediate and electrically in contact with each of said cathode electrode and said anode electrode such that said cathode electrode, said anode electrode and said solid electrolyte effect a primary electrical cell;

d) a heater disposed on the substrate;

e) a heater thermostat disposed on the substrate and connected to said heater and to a source of electrical energy so as to maintain said primary electrical cell within a predetermined temperature range;

f) said first metal, said second metal and the chemical composition of said electrolyte being further selected such that the voltage established between said cathode and said anode varies in accordance with the CO₂ concentration at said primary electrical cell when the temperature of said primary electrical cell is within said predetermined temperature range; and

2) CO₂ concentration modifying apparatus;

a) being responsive to the measurement of at least a first voltage level between said cathode and said anode representing a first predetermined CO₂ concentration for turning on said blower unit; and

b) being responsive to the measurement of at least a second voltage level between said cathode and said anode representing a second predetermined CO₂ concentration, higher than said first predetermined CO₂ concentration, for actuating said damper unit to admit outside air into the conditioned space.

8. The system of claim 7 in which said heater thermostat is set to maintain said electrical cell within the range of 225°

C. to 275°

C. and preferably at about 250°

C.

9. The system of claim 8 in which said first metal is platinum, said second metal is silver and said solid electrolyte is a mixture of Na₂CO₃, BaCO₃ and AG₂SO₄.

10. A system for monitoring and modifying the quality and temperature of air within a conditioned space which includes a blower unit, a damper unit for selectively admitting outside air into the conditioned space, a temperature moderating unit and a control unit, said control unit comprising:

A) a thermostat including temperature set point establishment means and temperature control means for selectively activating said temperature moderating unit when the temperature of the conditioned space deviates by a predetermined amount from the established temperature set point;

B) CO₂ concentration measuring and control apparatus for the conditioned space, said CO₂ concentration measuring and control apparatus being integral with said thermostat; and

C) CO₂ concentration modifying apparatus;

1) being responsive to the measurement by said CO₂ concentration measuring and control apparatus of at least a first predetermined CO₂ concentration for turning on said blower unit; and

2) being responsive to the measurement by said CO₂ concentration measuring and control apparatus of at least a second predetermined CO₂ concentration, higher than said first predetermined CO₂ concentration, for actuating said damper unit to admit outside air into the conditioned space.