Integrated furnace control board and method

• US 20040220777A1
• Filed: 04/23/2004
• Published: 11/04/2004
• Est. Priority Date: 04/29/2003
• Status: Abandoned Application

• Current Assignee: Sensata Technologies Incorporated (Sensata Technologies Holding Plc)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Li, Xun, St. Jean, David L., Johnson, Stephen S.
• Application Number:
  US10/830,777
• Publication Number:
  US 20040220777A1
• Time in Patent Office: Days
• US Class Current: 702/185
• CPC Class Codes: F23Q 23/00 Testing of ignition installations peculiar to internal-combustion engines F02P17/00
• CPC Class Codes: F23Q 7/24 Safety arrangements

Abstract

An electronic control (8) is shown adapted for use with gas furnaces which controls function and speed(s) of an induced draft motor (44), an igniter source (13), gas valve(s) (14), and function and speed(s) of a blower motor (21) based on inputs from a room thermostat, various sensor and safety devices, and proper sequence/position/change of position timing of these inputs. The control is capable of detecting and saving for recall specific errors and faults that occur while in service. The control can communicate warnings, faults, and errors, as well as safety lock-out conditions in various ways including a Light Emitting Diode (LED) (9), as a generic fault condition through a set of dry contacts (45a), or as very specific fault conditions through a communications interface (H4). The control provides other benefits to the installer, occupants of the space, and service technicians including selectable igniter warm-up times, user selectable fan On speed and blower delay-off times.

Claims

1. In a furnace system having serially connected safety devices and a control having a microprocessor for detecting an error condition and for assigning a unique error code for error events in the operation of the furnace, the method for distinguishing the appropriate error code for a sensed error condition in one of two types of serially connected safety devices, the first safety device being automatically resettable and having a reset time of a known selected time period and the second type of safety device being manually resettable, comprising the steps of:

detecting an error condition in the circuit containing the two types of serially connected safety devices,

initiating a time sequence at least as long as the known selected time period,

monitoring the circuit to determine if the circuit closes within the known selected time period,

if the circuit closes within the known selected time period then initiating an operational protocol based on the first safety device,

if the circuit remains open after expiration of the known selected time period then initiating an operational protocol based on the second safety device.

2. The method of claim 1 in which the furnace has a blower fan motor and an induced draft fan motor, a common operational protocol is provided for both the first and second types of safety devices including, stopping any existing ignition cycle and energizing the blower and induced draft fan motors, further comprising the steps of indicating an initial error code upon detection of an error condition in the circuit of the serially connected safety devices, and if the circuit closes within the selected time period then assigning an error code for the first type of safety device and continuing on with the operational protocol of the first safety device including de-energizing the blower and induced draft fan motors and returning to normal mode of operation.

3. The method of claim 1 in which the furnace has a blower fan motor and an induced draft fan motor, a common operational protocol is provided for both the first and second safety devices including, stopping any existing ignition cycle and energizing the blower and induced draft fan motors, further comprising the steps of changing the initial code to the second safety device error, saving the error code and time stamp and continuing on with the operational protocol of the second type of safety device including turning off the induced draft fan motor and maintaining the blower fan motor energized until one of clearing the error and powering down the control.

4. The method of claim 1 in which the error codes and associated time stamps are saved in a non-volatile memory location.

5. The method of claim 4 in which the non-volatile memory location is in the microprocessor.

6. The method of claim 4 in which the non-volatile memory location is in an EEPROM component.

7. The method of claim 1 in which the automatically resettable device is a high limit thermostat.

8. The method of claim 1 in which the manually resettable safety device is a flame roll-out sensor.