The heat-conveying medium is what carries the heat from the source to the enclosure being heated. The fuel used is a distinguishing characteristic of a heating system. Wood, coal, oil and gas are used to produce heat. Electricity may be considered a fuel, but it can also be the heat-conveying medium. The nature of the heat is also a distinguishing characteristic. For example, it could be steam, or heat produced by combustion. The efficiency and capacity of the heating system can be cited to distinguish one heating system from another.
The heating elements (radiators or vents) should be located in the coldest part of the room, typically next to the windows to minimize condensation and offset the convective air current formed in the room due to the air next to the window becoming negatively buoyant due to the cold glass. Devices that direct vents away from windows to prevent "wasted" heat defeat this design intent. Cold air drafts can contribute significantly to subjectively feeling colder than the average room temperature. Therefore, it is important to control the air leaks from outside in addition to proper design of the heating system.
Most heating system designs will located your heat vents or radiators under windows and close to doors, these areas are the coldest and providing most of the heat in these locations will ensure a more even heat through out that room or area. Devices that direct vents away from windows to prevent "wasted" heat defeat this design intent. Cold air drafts can contribute significantly to subjectively feeling colder than the average room temperature. Therefore, it is important to control the air leaks from outside in addition to proper design of the heating system.
Natural gas furnaces are by far the most popular type of central heating unit. Natural gas is about 85 to 90% methane (CH4). Burning natural gas (CH4) with oxygen yields carbon dioxide (CO2) and water vapor (2H2O) and heat. This is referred to as complete combustion. In reality, air is the source of oxygen (O2), and in the air, oxygen is mixed with some nitrogen. The resultant flue gas from the combustion will contain some nitrogen. Combustion is never complete (or perfect). In combustion exhaust gases, both unburned carbon (as soot) and carbon compounds (CO and others) will be present. Also, because air is the oxidant, some nitrogen will be oxidized into various nitrogen oxides (NOX).
Natural gas has no color, no odor, and it’s not toxic. It is highly combustible. It only smells because we put a scent in it. Natural gas has a specific gravity of about 0.6. Air has a specific gravity of 1. Natural gas is lighter than air. Propane has a specific gravity of 1.5, and a propane leak tends to pool on the floor surface and creates a dangerous situation. In a conventional gas furnace with a natural draft, air is mixed with the gas initially for combustion. This air is called the primary air. Primary air is controlled by the air shutters at the front of the burner assembly.
Natural draft refers to the burners of a conventional low-efficiency gas furnace. This type of burner is also called an atmospheric burner. With natural draft, we need to keep the chimney hot enough to get those combustion gases out of the chimney. Natural draft burners have no draft fan.
A forced draft is when the furnace has a fan that blows air into the combustion chamber through the heat exchanger and out through the venting system. All oil burners and some gas furnaces use forced draft. Forced draft has the fan before the burner. An induced draft uses a blower fan to pull air into the burner through the combustion chamber and exchanger. The fan is located on the exhaust-side of the exchanger. It also blows the flue gases out through the vent connector pipe. When the induced fan is operating, there is a negative pressure inside the heat exchanger. Induced-draft fans are also called exhaust blowers or power vents. Induced draft has a fan after the exchanger and before the vent pipe. Induced draft fans are common on mid-efficiency and high-efficiency furnaces.
Air conditioning is not simply the cooling of air. Air conditioning involves many aspects of conditioning or changing the air in whatever way in order to make the living environment for the occupants of a building comfortable. This may include warming the air, cooling the air, adding moisture, dehumidifying the air, filtering the air, and maintaining a balanced distribution or circulation of the air.
Your Professional Home Inspector is trained to inspect and operate your homes HVAC equipment. The Barrie Home Inspector has performed over 4,000 inspections and can provide you with a knowledgeable assessment of your homes heating, ventilation and air conditioning system. For Peace of Mind on your next Real Estate investment, call The Barrie Home inspector and ask for Roger.
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