Heating Systems
Furnaces, boilers, heat exchangers, combustion, steam systems, hydronic heating, and fuel types.
- Describe furnace types and combustion principles
- Explain boiler and steam system operation
- Identify hydronic heating components and heat exchanger types
- Compare heat pump heating and cooling modes
Lección 1
Furnaces & Combustion Principles
Furnace Types
A furnace heats air directly and distributes it through ductwork. Modern furnaces are categorized by efficiency:
Conventional (80% AFUE)
Single heat exchanger
Hot exhaust vented through chimney
Metal vent pipe (Type B)
80% of fuel energy becomes heat
Condensing (90-98% AFUE)
Two heat exchangers (primary + secondary)
Extracts latent heat from exhaust
PVC vent pipe (condensate forms)
90-98% of fuel energy becomes heat
Combustion Basics
Complete combustion of natural gas requires the correct ratio of fuel to air:
- Stoichiometric ratio: approximately 10 parts air to 1 part natural gas
- Excess air: additional air beyond stoichiometric for safety (typically 50% excess)
- Products: CO2, H2O, and N2 (complete combustion)
- Incomplete combustion produces CO (carbon monoxide) - a deadly hazard
Heat Exchanger Integrity
The heat exchanger separates combustion gases from the supply air. A cracked heat exchanger allows carbon monoxide to enter the living space - this is the most critical safety concern with furnaces.
Cracked Heat Exchanger
A cracked heat exchanger allows carbon monoxide (CO) to enter the supply air. This is a life-threatening condition. The furnace must be immediately shut down and the heat exchanger replaced.
Flame Characteristics
- Yellow/orange flame: incomplete combustion - CO being produced
- Blue flame with defined cones: proper combustion
- Lifting flame: too much primary air
- Delayed ignition: potential gas buildup before ignition
Condensing furnaces achieve 90-98% efficiency using a secondary heat exchanger to extract latent heat. A cracked heat exchanger allows CO into the living space and requires immediate shutdown. Complete combustion produces CO2 and H2O; incomplete combustion produces deadly CO.