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.
Hot water radiant heat is also found in older homes with some systems being added to newer homes via the hot water tank. The term radiator in this context is misleading since most heat transfer from the heat exchanger is by convection, not radiation. The radiators may be mounted on walls or buried in the floor to give under-floor heat.
The invention of central heating is often credited to the ancient Romans, who installed a system of air ducts called a hypocaust in the walls and floors of public baths and private villas. 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. This will help 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.
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).
Air conditioners use a refrigeration cycle which consists of four essential elements to create a cooling effect. The system refrigerant starts its cycle in a gaseous state. The compressor pumps the refrigerant gas up to a high pressure and temperature. From there it enters a heat exchanger (sometimes called a "condensing coil" or condenser) where it loses energy (heat) to the outside. In the process the refrigerant condenses into a liquid. The liquid refrigerant is returned indoors to another heat exchanger ("evaporating coil" or evaporator). A metering device allows the liquid to flow in at a low pressure at the proper rate. As the liquid refrigerant evaporates it aborbs energy (heat) from the inside air, returns to the compressor, and the cycle repeats. In the process, heat is absorbed from indoors, and transferred outdoors, resulting in cooling of the building.
The problem with using "rules of thumb" is that they are inherently imprecise. The idea is to estimate the size of an air-conditioning unit. The rule is one ton of refrigeration for each 500 to 700 square feet of floor area in the building. A ton of refrigeration is equivalent to 12,000 BTUs per hour. Determining the size of an air-conditioner system can be difficult. It can be done by reading the model number on the data plate of the outdoor condenser unit.
All modern air conditioning systems, down to small "window" package units, are equipped with internal air filters. These are generally of a light weight gauze-type element, and must be replaced as conditions warrant (some models may be washable). For example, a building in a high-dust environment, or a home with furry pets, will need to have the filters changed more often than buildings without these dirt loads. Failure to replace these filters as needed will contribute to a lower heat-exchange rate, resulting in wasted energy, shortened equipment life, and higher energy bills; also low air flow can result in "iced-up" or "iced-over" evaporator coils, and then there is no air flow at all. Additionally, very dirty or plugged filters can cause overheating during a heating cycle, and can possibly result in damage to the system or even fire.
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.
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.
Hot water radiant heat is also found in older homes with some systems being added to newer homes via the hot water tank. The term radiator in this context is misleading since most heat transfer from the heat exchanger is by convection, not radiation. The radiators may be mounted on walls or buried in the floor to give under-floor heat.
The invention of central heating is often credited to the ancient Romans, who installed a system of air ducts called a hypocaust in the walls and floors of public baths and private villas. 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. This will help 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.
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).
Air conditioners use a refrigeration cycle which consists of four essential elements to create a cooling effect. The system refrigerant starts its cycle in a gaseous state. The compressor pumps the refrigerant gas up to a high pressure and temperature. From there it enters a heat exchanger (sometimes called a "condensing coil" or condenser) where it loses energy (heat) to the outside. In the process the refrigerant condenses into a liquid. The liquid refrigerant is returned indoors to another heat exchanger ("evaporating coil" or evaporator). A metering device allows the liquid to flow in at a low pressure at the proper rate. As the liquid refrigerant evaporates it aborbs energy (heat) from the inside air, returns to the compressor, and the cycle repeats. In the process, heat is absorbed from indoors, and transferred outdoors, resulting in cooling of the building.
The problem with using "rules of thumb" is that they are inherently imprecise. The idea is to estimate the size of an air-conditioning unit. The rule is one ton of refrigeration for each 500 to 700 square feet of floor area in the building. A ton of refrigeration is equivalent to 12,000 BTUs per hour. Determining the size of an air-conditioner system can be difficult. It can be done by reading the model number on the data plate of the outdoor condenser unit.
All modern air conditioning systems, down to small "window" package units, are equipped with internal air filters. These are generally of a light weight gauze-type element, and must be replaced as conditions warrant (some models may be washable). For example, a building in a high-dust environment, or a home with furry pets, will need to have the filters changed more often than buildings without these dirt loads. Failure to replace these filters as needed will contribute to a lower heat-exchange rate, resulting in wasted energy, shortened equipment life, and higher energy bills; also low air flow can result in "iced-up" or "iced-over" evaporator coils, and then there is no air flow at all. Additionally, very dirty or plugged filters can cause overheating during a heating cycle, and can possibly result in damage to the system or even fire.
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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