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 gravity warm-air furnaces rely primarily on gravity for circulating the heated air. Warm air is lighter than cool air and will rise and move through ducts and pipes. After releasing its heat, the air becomes cooler and heavier. The air drops down the structure through return registers to the furnace where it is heated again, and the cycle continues. The very earliest types of furnaces were gravity-type furnaces. Sometimes, they had a blower fan installed to move the heated air. They have mostly been replaced by modern, forced warm-air furnaces.
“Mechanical” or “forced” ventilation is provided by an air handler and used to control indoor air quality. Excess humidity, odors, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates much energy is required to remove excess moisture from ventilation air.
Kitchens and bathrooms typically have mechanical exhaust to control odors and sometimes humidity. Factors in the design of such systems include the flow rate (which is a function of the fan speed and exhaust vent size) and noise level. Direct drive fans are available for many applications, and can reduce maintenance needs.
Natural gas is the most popular of fuels in built up areas due to its price and convenience. For your furnace to ignite natural gas, you need a mixture of gas and air that is conducive to ignition. If you have too little air in the mix, the gas will not ignite. If you have too much air, the gas will not ignite. You have to have between about 86% air to 94% of air mixed with a certain gas volume to get the gas to ignite. Once ignited, the ignition temperature of natural gas is about 1,200 F. That’s hot. The remainder of the air mixture comes from the air that actually surrounds the flames inside the combustion chamber. This air is called the secondary air. The secondary air (the air around the flames) and the primary air (the air drawn into the burners) combine to make up the total combustion air.
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.
Central, ‘all-air’ air conditioning systems (or package systems) with a combined outdoor condenser/evaporator unit are often installed in modern residences, offices, and public buildings, but are difficult to retrofit (install in a building that was not designed to receive it) because of the bulky air ducts required to carry the needed air to heat or cool an area. The duct system must be carefully maintained to prevent the growth of pathogenic bacteria such as legionella in the ducts.
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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