Limit Switch Tripping – 95%, 2-Stage Gas Furnaces
Type: Service Alert
Recall or Alert Date: 09-08-2008
Serial Number: FURN-SVB29A-EN
Brands Affected: American StandardTrane
Issue with the high temperature limit switch operation in 95% AFUE, 2-Stage Residential Gas Furnaces. This bulletin is not being issued to address any safety issue or concern.
We have received isolated reports on affected models of nuisance tripping on the high temperature limit control. Lab testing of field returned furnaces has indicated a
misdirected airflow was present within the heat exchanger assembly. The misdirected airflow was caused by some of the fins on the “leaving air” side of the secondary heat exchanger (the recoup cell) being bent. This creates reduced airflow over the high temperature limit control causing the control to open. The affected serial number range is 7212***** through 8075*****.
If the problem persists on the models *UH2B080A9V3VAA or *UH2D120A9V5VAA there is a replacement limit switch kit (KIT15182) available. This kit contains a higher setting limit switch (230°F) and a label to indicate that the furnace has been retrofitted with the higher temperature switch. The label is in the kit to help ensure any future limit switch replacement on that particular furnace does not revert to the original part.Affected Products:
Models Beginning serial Ending Serial
AUH2B080A9V3VA 7212* 8075*
AUH2D120A9V5VA 7212* 8075*
TUH2B080A9V3VA 7212* 8075*
TUH2D120A9V5VA 7212* 8075*