Warmup method for a two stage furnace

• US 4,976,459 A
• Filed: 02/09/1990
• Issued: 12/11/1990
• Est. Priority Date: 02/09/1990
• Status: Expired due to Term

• Current Assignee: International Comfort Products Corp. (Carrier Global Corporation)
• Original Assignee: Inter-City Products Corporation
• Inventors: Lynch, Gregory A.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US07/478,206
• Time in Patent Office: 305 Days
• Field of Search: 236/1 EB, 236/10, 236/11, 236/DIG. 9, 165/12, 126/112
• US Class Current: 236/11
• CPC Class Codes: F23N 1/022 using electronic means
• CPC Class Codes: F23N 2223/08 Microprocessor; Microcomputer
• CPC Class Codes: F23N 2227/04 Prepurge
• CPC Class Codes: F23N 2227/06 Postpurge
• CPC Class Codes: F23N 2227/16 Checking components, e.g. electronic
• CPC Class Codes: F23N 2227/28 Ignition circuits
• CPC Class Codes: F23N 2229/00 Flame sensors
• 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 2237/10 High or low fire
• CPC Class Codes: F23N 5/203 using electronic means

Abstract

The present invention involves a two stage furnace and a method of warming its heat exchanger. The furnace includes a gas valve with low and high combustion settings, and inducer and circulator fans with low and high speed settings. When a call for heat is present, the inducer fan and gas valve operate at high. After a heat on delay period, the circulator fan operates at low speed to provide an initial warm stream of air from the furnace.

Claims

1. In a two stage furnace having a gas burner and at least one heat exchanger, a method of initially warming the heat exchanger comprising the steps of:

providing a gas valve having a low and high combustion operating setting, an inducer fan having a low and high speed operating setting, and a circulator fan having a low and high speed operating setting;

determining that the furnace has been enabled;

operating said gas valve on said high combustion setting and said inducer fan or said high speed setting;

delaying said circulator fan by a predetermined heat on delay and then operating said circulator fan at said low speed setting;

determining when a predetermined warmup time has expired, and after expiration operating said gas valve, said inducer fan, and said circulator fan at one of the combustion settings.

2. A two stage furnace comprising:

a plenum having a combustion chamber and a heat exchanger, an inducer fan in communication with the combustion chamber, a circulator fan in communication with the heat exchanger, each of said inducer fan and said circulator fan having a low and high speed operating setting;

a gas burner in communication with said combustion chamber;

a gas valve fluidly connected to said gas burner, said gas valve having a low and high combustion operating setting;

an ignitor located adjacent to said gas burner;

means for determining that said furnace has been enabled, said determining means including means for operating said inducer fan on said high speed setting and said gas valve o said high combustion setting when said determining means initially determines that said furnace has been enabled; and

means for delaying operating said circulator fan for a predetermined heat on delay and then operating said circulator fan on said low speed setting, said delaying means including means for timing a predetermined warmup time and operating said inducer fan and said circulator fan at one of said combustion settings after expiration of said predetermined warmup time.