Combustion appliances have heat exchangers. In an all-electric appliance, you can draw the house air directly across the warm refrigerant or strip coils to condition the interior. In a combustion appliance, you must keep the byproducts of the burning fuel out of the air being delivered to the home. This is done with a heat exchanger. The flames are confined to a combustion chamber, which is connected to the flue system. Between these is the heat exchanger(s). In a furnace the heat conducts through the metal of the sealed exchanger, and the house air captures it as it passes on the other side. In a boiler, the circulating water is routed in tubes through the combustion air stream, gaining its heat as it passes. In this section we will also look at combustion chamber issues.
The main problem with inspecting heat exchangers is that they aren’t fully visible. Report any rust or damage in the areas that you can see. Be alert to combustion odors in the house. Watch the furnace’s flames when the blower engages; a disruption implies heat exchanger damage. Use the available heat exchanger Limitation Statement as appropriate.
The heat exchanger is rusted. Cracks or gaps permit flue gases to enter the living spaces. System replacement may be required. Hire an HVAC contractor to evaluate the system and to make required repairs.
The heat exchanger is cracked. This permits exhaust flue gases to enter the living spaces. The system should be turned off and not used. System replacement may be required. Hire an HVAC contractor to evaluate the system and to make required repairs.
There is diversion in the furnace’s burner flames when the circulator fan starts. This implies a possible hazardous failure in the heat exchanger. System replacement may be required. Hire an HVAC contractor to evaluate the system and to make required repairs.
The combustion chamber is cracked. This is a safety hazard that can allow further damage. Hire an HVAC contractor to evaluate the system and to make required repairs.
The combustion chamber is deteriorated. This is a safety hazard. Replacement of the chamber, and possibly the appliance, is required. Hire an HVAC contractor to evaluate the system and to make required repairs as needed.
