Multi-stage electric heater apparatus and method of control

• US 3,932,729 A
• Filed: 10/23/1974
• Issued: 01/13/1976
• Est. Priority Date: 10/23/1974
• Status: Expired due to Term

• Current Assignee: American Standard Companies Incorporated (Ideal Standard International Topco SCA)
• Original Assignee: Trane Company (Trane Technologies plc)
• Inventors: Schlangen, Andrew J.
• Primary Examiner(s): Envall, Jr., R. N.
• Assistant Examiner(s): Bell, Fred E.
• Application Number:
  US05/517,075
• Time in Patent Office: 447 Days
• Field of Search: 219/480, 219/483, 219/484, 219/486, 219/487
• US Class Current: 219/486
• CPC Class Codes: G05D 23/1912 whose output amplitude can take more than two discrete values
• CPC Class Codes: G05D 23/275 with sensing element expanding, contracting, or fusing in response to changes of temperature

Abstract

An electric heater control circuit is shown which utilizes a 10-step controller for obtaining eighteen steps of heating control. Electrical and magnetic control circuitry operates this 10-step controller effectively through two cycles, one at a low level power output mode and a second at a high level power output mode, to thereby substantially increase the effective number of steps of heat control. In addition, means are provided for instantaneously energizing or de-energizing a plurality of small electric heaters upon shifting modes to compensate for the de-energization or energization respectively of a large heater to thereby avoid momentary periods of excess heat or cold while the controller is shifting modes.

Claims

1. A method of controlling a plurality of electric heaters for heating a space including one large heater and a plurality of smaller heaters, each of said large and small heaters having a separate actuator means for actuating its respective heater toward an energized condition comprising the steps upon a continuous heating demand as sensed by a thermostat responsive to the temperature of said space of:

A. sequentially actuating said actuator means of said smaller heaters toward their heater energizing conditions;

B. subsequently deactuating said actuator means of said smaller heaters toward their heater de-energizing condition and actuating said actuator means for said larger heater toward its heater energizing condition; and

C. subsequently sequentially reactuating said deactuated actuator means until all of said actuator means for said large and smaller heaters are actuated toward their heater energizing condition.

2. The method as defined by claim 1 wherein said deactuated actuator means are deactuated sequentially in step B in the reverse order that they are actuated in step A.

3. The method as defined by claim 1 including the step prior to step B of simultaneously disabling all of said actuator means to be sequentially deactuated in step B.

4. The method as defined by claim 2 including the step of disabling said thermostat while said actuator means are being sequentially deactuated.

5. A system (20) for controlling the temperature of space (18) comprising:

one large capacity electric heater means (H11) for heating said space;

a plurality of smaller capacity electric heater means (H1-H10) for heating said space;

a step controller means (25) for controlling the operation of said large and smaller capacity electric heater means;

said step controller means including a plurality of sequentially actuatable controller switches (S1-S10) operatively associated with said heater means including a first, second, third, fourth, fifth switches (S1, S2, S3, S4, S9) respectively operatively associated with first, second, third, fourth, fifth (H1, H2, H3, H4, H9) of said smaller capacity heater means, and a sixth switch (S10) operatively associated with said large capacity heater means (H11), cam means (38) for sequentially actuating said first, second, third, fourth, fifth and sixth controller switches and a reversable cam motor (26) drivingly connected to said cam means;

first motor circuit means (32) for energizing said motor to drive said cam means in a forward direction for sequentially actuating said first, second, third, fourth, fifth and sixth switches toward a first (A) position;

second motor circuit means (36) for energizing said motor to drive said cam means in a reverse direction for sequentially actuating said sixth, fifth, fourth, third, second and first switches toward a second position (B);

a thermostat (46) operatively associated with said first and second motor circuit means to energize said first motor circuit in response to a demand for additional heat at said space and to energize said second motor circuit in response to a demand for reduced heat at said space;

first means (12R, 12R4, and 12R3) overriding said thermostat for energizing said motor to drive said cam means in a reverse direction;

second means (13R, 13R3 and 13R4) overriding said thermostat for energizing said motor to drive said cam means in a forward direction;

holding means (S1 and 11R2) responsive to actuation of said sixth switch toward its heater energizing position (A) for holding said large heater means energized despite subsequent actuation of said sixth switch to a heater non-energizing position (B); and

means (11R3) operatively associated with said sixth switch for actuating said first overriding means whereby upon a continued demand for additional heat as sensed by said thermostat, said cam means is first driven in a forward direction sequentially energizing said smaller heater means and then said larger heater means whereupon via said holding means and said first overriding means said large heater means is held energized and said cam is driven in the reverse direction.

6. The apparatus ad defined by claim 5 including means (2R2) operatively associated with said second switch (S2) for deactivating said first overriding means whereby the position of said cam means is again placed under the control of said thermostat.

7. The apparatus as defined by claim 6 including means (1R2) operatively associated with said first switch (S1) for activating said second overriding means to drive said cam means in a forward direction;

and means (S1) operatively associated with said first switch (S1) for disabling said holding means (S1 and 11R2).

8. The apparatus as defined in claim 7 including means (9R2) operatively associated with said fifth switch (S9) for deactivating said second overriding means (13R, 13R3, and 13R4).

9. The apparatus as defined by claim 5 including heater disabling means (12R, 12R2) for substantially simultaneously de-energizing a plurality (H3, H4, H9) of said smaller heater means and means (11R3) operatively associated with said sixth switch (S10) for actuating said heater disabling means (12R and 12R2).

10. The apparatus as defined by claim 9 including means (2R2) operatively associated with said second switch (S2) for interrupting said disabling means.

11. The apparatus as defined by claim 7 including heater energizing means (13R, 13R2) for substantially simultaneously energizing a plurality of said smaller heater means (H3, H4 and H9) and means (1R2) operatively associated with said first switch (S1) for actuating said heater energizing means.

12. The apparatus as defined by claim 11 including means (9R2) operatively associated with said fifth switch (S9) for interrupting said heater energizing means.