The duct furnace or furnace module should be inspected annually by a qualified service agency. The condition of the burners, heat exchanger, draft inducer, vent system, operating controls and wiring should be determined. Check for obvious signs of deterioration, accumulation of dirt and debris, and heat or water related damage. Any damaged or deteriorated parts should be replaced before the unit is put back into service.
Label all wires prior to disconnection when servicing unit, Wiring errors can cause improper or dangerous operation. Verify proper operation after servicing.
Inspect burners, heat exchanger, induced draft fan and vent ducts and clean as necessary.
Check the heat exchanger for cracks. If any are present, replace heat exchanger before putting unit back into service.
Check the attachment points of the duct furnace to the cabinet to verify that they are air-tight. For a rack system module, check the attachment points to the cabinet or ducts to verify that they are air-tight.
Check the automatic gas valve to ensure that the gas valve seat is not leaking.
Check wiring connections to be sure they are secure, and inspect wiring for any deterioration.
If any of the original wiring needs to be replaced, it must be replaced with wiring materials suitable for 221°F (105°C). Unsuitable wiring materials may cause equipment damage.
Source: Carrier (www.shareddocs.com)