35” Condensing Gas Furnace Nuisance Pressure Switch Tripping
Type: Service Alert
Recall or Alert Date: 01-20-2014
Serial Number: DSB 14-0002
Brands Affected: BryantCarrierPayne
The inducer housing pressure switch (HPS) on single stage models is opening during furnace operation. This appears to the homeowner as a non-functioning furnace. Site visits and testing have determined the primary cause of this issue to be installation related; specifically, incorrect venting and condensate drainage. However, it is possible for nuisance pressure switch tripping to occur from the following phenomenon.
Condensed flue gas droplets can migrate into the inducer housing pressure port. Most installations pull in cold combustion air during the inducer pre-purge. The cold air chills the inducer housing, which causes flue gas condensation droplets to form during the first few minutes of operation. The condensation droplets can migrate into the pressure tap and tube (through the capillary affect) and momentarily block the pressure signal to the inducer HPS. If the furnace runs long enough, the
inducer housing heats up enough to prevent condensation droplet formation.
Condensation droplets can form during the first few minutes after a call for heat. If the pressure switch opens within the first few minutes, the furnace does not provide enough heat to keep the home warm.
Two stage models that start on high stage can experience the same issue as single stage models.Two stage models that start in low stage, then transition to high stage, do not experience nuisance switch tripping from condensate droplets. The HPS is called the high heat pressure switch on two
Modulating furnaces do not use inducer housing pressure, so the field corrective action does not apply.Affected Products:
All sizes except the 140k input in the following model families:
Carrier: 59SC2A, 59SC2B, 59SC5A, 59SP5A, 59TP5A, 59TN6A
Bryant: 912SA, 912SB, 915SA, 925SA, 925TA, 986TA
Payne: PG92SAS, PG92SBS, PG95SAS, PG95XAT
Serial Numbers: 2711A to 5313