Method for providing variable output gas-fired furnace with a constant temperature rise and efficiency

• US 4,688,547 A
• Filed: 07/25/1986
• Issued: 08/25/1987
• Est. Priority Date: 07/25/1986
• Status: Expired due to Term

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Thompson, Kevin D., Ballard, Gary W.
• Primary Examiner(s): Jones, Larry
• Application Number:
  US06/889,152
• Time in Patent Office: 396 Days
• Field of Search: 236/10, 236/11, 236/15 BD, 236/15 BG, 236/46 R, 236/46 E, 236/46 F, 236/DIG. 8, 126/110 E, 126/99 R, 126/110 R, 126/116 A, 165/13, 165/16, 165/26, 237/2 R, 237/2 A, 237/53
• US Class Current: 126/116.00A
• CPC Class Codes: F23N 1/022 using electronic means
• CPC Class Codes: F23N 2223/08 Microprocessor; Microcomputer
• CPC Class Codes: F23N 2225/04 pressure
• CPC Class Codes: F23N 2225/12 room temperature
• CPC Class Codes: F23N 2227/06 Postpurge
• CPC Class Codes: F23N 2233/08 with variable speed
• CPC Class Codes: F23N 2233/10 forcing air through heat exchangers
• CPC Class Codes: F23N 2235/14 electromagnetically operated
• CPC Class Codes: F23N 2235/24 Valve details
• CPC Class Codes: Y10S 236/08 Computer
• CPC Class Codes: Y10S 236/09 Fan control

Abstract

A furnace is operated such that the air-fuel ratio and the temperature rise are maintained constant so that the efficiency remains constant over the range of operation.

Claims

1. A method for providing a variable output gas-fired furnace means with a constant temperature rise and efficiency where the furnace means includes burners, a blower, a thermostat and a delay timer, the method comprising the steps of:

sensing the temperature in an area to be conditioned;

comparing the sensed temperature to a predetermined set point;

if the sensed temperature deviates from the predetermined set point by more than a predetermined amount, gas is supplied to the burners and the blower is started;

determining the reference revolution per minute of the blower;

determining the reference cubic feet per minute delivered by the blower;

determining the manifold pressure;

determining whether the furnace is in a high heat or a low heat mode of operation;

determining the desired cubic feet per minute delivered by the blower for the current mode of operation;

reading the actual revolution per minute of the blower;

adjusting the speed of the blower motor if the actual and desired revolution per minute of the blower are not the same;

determining whether the thermostat is satisfied;

if the thermostat is not satisfied, returning to the step of determining the manifold pressure; and

if the thermostat is satisfied, shutting off the gas and starting the delay timer.

2. The method of claim 1 further included the steps of:

continuing to adjust the speed of the blower if the actual and desired revolution per minute of the blower are not the same until the delay timer times out; and

shutting off the blower when the delay timer times out.