HVAC - Heating

Heating

There are many different types of heating systems. Central heating is often used in cold climates to heat private houses and public buildings. Such a system contains a boiler, furnace, or heat pump to heat water, steam, or air in a central location such as a furnace room in a home or a mechanical room in a large building. The use of water as the heat transfer medium is known as hydronics. These systems also contain either ductwork for forced air systems or piping to distribute a heated fluid and radiators to transfer this heat to the air. 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.

Most modern hot water boiler heating systems have a cirulator, which is a pump to send hot water to the distribution system. This distribution system can be via radiators, convectors (baseboard), hot water coils (hydro-air) or other heat exchangers. The heated water can also supply a heat exchanger located internally or externally and store hot water in a tank to supply domestic hot water for bathing and washing.

Warm air systems distribute heated air through ductwork systems of supply and return air metal or fiberglass ducts. Many system use the same ductwork to distribute air cooled by an evaporator coil for air conditioning. The air supply is typically filtered or passed through air cleaners to remove dust and pollen particles.

One heat source is electricity, where heaters that are made with high resistance wire get hot from the resistance to electric flow. This principle is also used for baseboard heaters, and portable heaters. Electrical heaters are ofter used as backup or supplemental heatsd for heat pump (or reverse heating) systems.

The heat pump is a form of heating that gained popularity in the 1950’s. Heat pumps can extract heat from the air (air source) or from the ground (ground source). Traditionally heat pump HVAC systems were specified in more moderate climates, but with improvements in low temperature operation and reduced heat loads due to more efficient homes the are increasing in popularity. Heat pumps can be air to air, air to water, water to air and water to water systems. When we use water on the supply side of the heat pump it typicall is geothermal energy from ground water, surface water or PEX tubing buried in a deep trench. With the wells and site work the geothermal system water type heat pumps are typically more expensive equipment to purchase and install than conventional heating systems.

The invention of central heating is often credited to the ancient Romans, who installed systems of air ducts called hypocausts in the walls and floors of public baths and private villas.

The use of furnaces, space heaters and boilers as means of indoor heating may result in incomplete combustion and the emission of carbon monoxide, NOx, formaldehyde, VOC’s and other combustion by-products. Incomplete combustion occurs when there is insufficient oxygen; the inputs are fuels containing various contaminants and the outputs are the harmful by-products, most dangerously carbon monoxide which is a tasteless and odorless gas that has serious adverse health effects when inhaled.

Without proper ventilation, carbon monoxide can be extremely dangerous and can vary from a small, limited amount to a lethal amount. Carbon monoxide can be lethal at high concentration, usually less than 1000 ppmv. However, at several hundred ppmv, carbon monoxide exposure can induce headaches, fatigue, nausea and vomiting. Carbon monoxide binds with hemoglobin in the blood, forming carboxyhemoglobin, reducing the blood’s ability to transport oxygen. The primary health concerns associated with carbon monoxide exposure are its cardiovascular and neurobehavioral effects. Carbon monoxide can cause atherosclerosis; the hardening of arteries, and can also trigger heart attacks. Neurologically, carbon monoxide exposure reduces hand to eye coordination, vigilance and continuous performance. It can also affect your time discrimination.