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2.1: Types of Heating Systems (Gas Fire Furnace and Heat Pumps)

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    Understanding Gas Furnaces and Heat Pumps

         In the world of HVAC, not all heating systems are created equal. Depending on the climate, building type, energy costs, and customer preferences, technicians may encounter a range of systems—each with its own benefits, components, and service requirements. In this chapter, we'll focus on two of the most common residential heating systems: the gas-fired furnace and the heat pump.

         A gas furnace is a traditional system that uses natural gas or propane to generate heat. It’s especially common in colder climates where consistent and powerful heating is needed during the winter months. When the thermostat signals for heat, the furnace ignites gas in a burner, heats up a heat exchanger, and blows warm air through the ductwork.

         In contrast, a heat pump doesn’t burn fuel to create heat. Instead, it uses electricity and refrigerant to move heat—either extracting it from the outdoor air or the ground and transferring it indoors. Heat pumps are energy-efficient and can provide both heating and cooling, making them a versatile choice for milder climates.

         Throughout this chapter, you'll learn how each system operates, the key components involved, how to identify them in the field, and when each system is the better choice. You’ll also explore efficiency ratings, maintenance needs, and installation considerations so you're prepared to service and explain these systems to customers.

     

    Image: The Air Handler of the Heat Pump

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    🔥 Gas-Fired Furnace (Forced-Air Furnace) – Definition:

         A gas-fired furnace is a combustion-based heating system that uses natural gas or propane as its fuel source. It operates by burning gas inside a heat exchanger, then using a blower fan to distribute the heated air through the ductwork of a building. This is a dry heat system, meaning it only provides heating, not cooling.

     

    🔧 Key Components:

    • Gas burner – Where fuel is ignited

    • Heat exchanger – Transfers heat from combustion gases to the air

    • Blower motor/fan – Pushes heated air into the ductwork

    • Flue or vent – Exhausts combustion gases safely outside

    • Control board and safety devices – Includes limit switches, flame sensor, and gas valve

     

    ⚙️ How It Works:

    1. Thermostat calls for heat

    2. Gas valve opens and burner ignites

    3. Heat exchanger warms up

    4. Blower fan turns on and blows air over the heat exchanger

    5. Heated air is distributed through the house via ductwork

    6. Exhaust gases exit through flue

     

    ✅ Advantages:

    • Strong heat output in very cold climates

    • Low operating cost when natural gas is affordable

    • Long-lasting and reliable with proper maintenance

     

    ♻️ Heat Pump – Definition:

         A heat pump is an electric HVAC system that moves thermal energy from one place to another using refrigerant and a vapor-compression cycle. In heating mode, it pulls heat from the outside air (or ground, in geothermal systems) and transfers it indoors. In cooling mode, it works just like an air conditioner—removing heat from the inside and releasing it outdoors.

     

    🔧 Key Components:

    • Compressor – Pressurizes and circulates refrigerant

    • Reversing valve – Changes the direction of refrigerant flow for heating vs. cooling

    • Indoor and outdoor coils (evaporator/condenser) – Transfer heat

    • Expansion valve – Controls refrigerant pressure

    • Air handler – Contains blower and indoor coil (often paired with electric backup heat strips)

     

    ⚙️ How It Works (in Heating Mode):

    1. Thermostat calls for heat

    2. Reversing valve sends refrigerant to absorb heat from outside air

    3. Compressor pumps warm refrigerant to the indoor coil

    4. Indoor air handler blows room air across the warm coil

    5. Heated air is sent through ductwork into the building

     

    Scotsman Heat Pump

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    ✅ Advantages:

    • Can provide both heating and cooling

    • Very energy-efficient, especially in moderate climates

    • Environmentally friendly (no combustion emissions)

    • Eligible for rebates and tax incentives in many regions

     

    🔍 Comparison Summary:

    Feature Gas-Fired Furnace Heat Pump
    Fuel Source Natural gas or propane Electricity
    Heating Method Burns gas to generate heat Moves heat using refrigerant cycle
    Cooling Capability ❌ No ✅ Yes
    Best For Cold climates Mild to moderate climates
    Efficiency 80–98% AFUE (depends on model) 200–300% efficient (COP > 1.0)
    Environmental Impact Emits CO₂ through combustion Lower carbon footprint (no combustion)
    Installation Cost Generally lower Higher initial cost, but long-term savings

     

    2.1: Types of Heating Systems (Gas Fire Furnace and Heat Pumps) is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.