Home Heating Glossary

Active Solar Heating - See, Solar Heating/Cooling

AFUE - Annual Fuel Utilization Efficiency (AFUE) ratings are a measure of the thermal efficiency of a boiler or furnace as determined by U.S. government standards. The higher the rating, the greater the heating efficiency of the unit. New furnaces and boilers must display their AFUE so that consumers can compare ratings. See a detailed explanation of AFUE ratings here.

Air Scoop - Device that removes dissolved air from the fluid in a hydronic (water) heating/cooling system to prevent noise in the system.

Air Separator - Device that removes dissolved air from the fluid in a hydronic (water) heating/cooling system to prevent noise in the system.

Air Source Heat Pump - A pump that uses outside air as the heat source. See, Heat Pump.

Air Vent - In a hydronic central heating system, device that removes dissolved air from the fluid in a hydronic heating/cooling system to prevent noise in the system.

Blower - A device used to move air through a forced air central heating system. See, Forced Air Heating/Cooling.

Boiler - In a hydronic central heating system, a device used to heat the water used as the heat transfer medium.

BTU (British Thermal Unit) - The fundamental unit of measurement of heat. The quantity of heat need to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

Central Heating/Cooling - A heating system in which air or water is heated at a central location and distributed throughout the building via a network of pipes or ducts.

Circulator - What most people call a pump. A circulator is a mechanical device that moves fluid, usually water, through a closed loop system, such as a central heating/cooling system. See, Pump

Differential Bypass Valve - In a hydronic central heating system using zone valves, a device to control excess flow in the system in response to changes in the heating demand. See, Taco Differential Bypass Valves.

D-MAND System - Taco's domestic hot water recirculation system that saves water, energy, and fuel costs. See, Domestic Hot Water Recirculation.

Domestic Hot Water Recirculation System - A home hot water system that recovers heat energy from drain water and recirculates the heat to the hot water supply piping. Domestic hot water recirculation systems can save tens of thousands of gallons a year (14,000 gallons annually for a family of four, according to the U.S. Department of Energy), reduce energy use and save energy dollars. Taco's D'MAND System is one example. Also called "instant" or "on-demand" hot water systems. (See, Energy Saving Tips.)

EBV Zone Valve - Taco Electronic Ball Valve, [link to product page] a "smart" device that controls the flow of system water (fluid) in a hydronic central heating system for enhanced comfort and energy savings in all zones of the structure. The Taco EBV contains a microprocessor that automatically reacts to the heat requirements of each zone in the system.

Expansion Tank - In a hydronic central heating system, a pressurized tank that helps to maintain proper system pressure as system water expands or contracts as it heats and cools.

Forced Air Heating/Cooling - A central heating system that uses air as the heat transfer medium. Forced air systems use a fan or blowers to circulate air. Gravity systems have no blower to aid circulation.

Furnace - In an air-based central heating system, the device used to heat air for distribution throughout the building. There are several types of furnace. The most common burn gas or oil, however a furnace can be coal fired or use electricity as the energy source.

Geothermal Energy - Energy derived from the heat under the surface of the Earth. This energy was created from the original formation of the planet. Most commonly it comes to the surface in volcanic eruptions and hot springs. In geologically active areas, large amounts of geothermal energy are often used for the commercial generation of electricity.

Geothermal Heating/Cooling - The direct use of geothermal energy for heating or cooling, as in a home central heating or supplemental heating system.

Geothermal Heat Pump - A pump used to transfer heat from the ground for use in a geothermal heating/cooling system. Also called a ground source heat pump.

Ground Source Heat Pump - See, Geothermal heat pump.

Heat Conduction - Heat energy that is transferred from molecule to molecule within a substance (solid, liquid or gas).

Heat Convection - Heat energy that is transferred within fluids or gases. Forced air heating/cooling systems rely on convection.

Heat Exchanger - A device that transfers heat from one medium to another. In an air-based central heating system a heat exchanger transfers heat from the furnace to the air, which then circulates through the structure.

Heat Motor Zone Valve - In a hydronic central heating system, a device that controls the flow of system water (fluid) to provide individual room or area comfort and energy savings. See, Taco Heat Motor Zone Valves.

Heat Pump - A pump used to transfer thermal energy (heat) from one location to another. Heat pumps can extract heat from air, water or the Earth (geothermal energy) Heat pumps may be air source or ground source (geothermal) pumps.

Hot Water Heating - See, Hydronic Heating

Hydronic Heating/Cooling - A central heating system that uses water (or other fluid such as a water/antifreeze mix) as the heat transfer medium for heating (and/or cooling).

Indirect Water Heater - A water heater that circulates water through a heat exchanger in the boiler to heat water, rather than in a separate, free-standing tank.

Instant Hot Water System - See, Domestic Hot Water Recirculation System.

ISeries Mixing Valve - Taco products that provide precise and cost-effective temperature control in a hydronic central heating system. See, Taco Iseries Mixing Valves.

Low Water Cutoff - In a hydronic central heating system a device that detects the fluid level in hot water and steam boilers and reacts when the level falls below the minimum safe operating level. See, Taco Low Water Cut Off

Mixing Valve - In a hydronic central heating system, a device that controls mixing of hot and cold water for the desired water temperature. Also, shuts off water supply in the event of failure. See, Taco Pressure and Mixing Valves.

On-Demand Hot Water System - See, Domestic Hot Water Recirculation System.

Outdoor Reset Circulator - Circulator in a hydronic heating/cooling system that automatically regulates system water temperature based on the outdoor temperature and the changing heat load on the structure. See, Taco Variable Speed Outdoor Reset "00" Circulator.

Passive Solar Heating - See, Solar Heating/Cooling

Pressure Reducing Valve - In a hydronic central heating system, a device that reduces street water pressure (from a municipal system) to a suitable level for the domestic system, usually 12 PSI.

Pressure Relief Valve - In a hydronic central heating system, a device that prevents excess pressure from building in the boiler and distribution piping.

Pump - A mechanical device that uses suction or pressure to raise or move liquids, compress gases, etc. See, Circulator.

Radiant Heating/Cooling - System that uses radiant energy to warm the room or structure. Hydronic heating systems provide radiant heating, for example, through cast iron radiators or baseboard convectors, for example. Underfloor heating systems also use radiant heat.

Radiant Heat - Heat energy that is transferred from one body to another that are not in contact. In a hydronic heating system, for example, hot water heats cast iron radiators or baseboard convectors which in turn transfer heat to the objects and people in the room.

Radiant Mixing Block - Taco product that is a complete injection mixing system in one, integrated package for radiant heating systems. Includes variable speed injection mixing control, injection circulator, system circulator and aid elimination in a single unit. See, Taco Radiant Mixing Block.

Radiator - A device that acts as a heat exchanger in a hydronic central heating system to provide radiant heat throughout the building.

Return Ducts - The channels used in air-based central heating systems to return cooler air to the furnace (after it has transferred its heat throughout the structure).

Solar Energy - Energy from the Sun that strikes the Earth. Solar energy can be used in several ways for heating or to generate electrical energy.

Solar Heating/Cooling - The use of solar energy for space or water heating. Solar heating systems may be passive or active. Passive solar heating systems capture the sun's heat within the building and building materials for later release. Active solar heating systems collect heat energy from the sun in either air or liquid (water/antifreeze) then transfer the energy to the interior space or to a storage system from which the heat is later distributed.

Solar X-Pump Block - Taco product that offers complete thermal solution for design, control and installation of solar thermal systems in one, integrated system. See, Taco Solar X-Pump Block. See also, X-Pump Block.

Supply Ducts - The channels used in air-based central heating systems to distribute heated air through the structure.

Underfloor Heating - A system that uses radiant heat to warm a room or structure. Underfloor heating consist of a network of pipes or tubing through which water is circulated. Tubing or cable is generally set into a concrete slab or within the sub-floor structure.

Variable Speed Circulator - A circulator that changes speed to deliver optimum comfort and energy efficiency from a hydronic heating/cooling system. Taco Delta-T circulators respond to the actual supply and return water temperature readings at any given time to maintain the design difference between them (Delta-T) by creating just the right amount of flow through the system, so that the system performs as designed.

WAGS Valve - Taco's Water And Gas Shut-off Valve (WAGS) for electric and gas water heaters. When a water heater fails it can cause flooding and damage to the home and personal possessions. The WAGS Valve automatically shuts off the water supply, and gas supply on gas-fired water heaters, in the event of a water heater leak.

X-Pump block - Taco all-in-one solution for the design, control and installation of radiant systems that includes a variable speed mixing control, heat source circulator, systems circulator and heat exchanger in a single unit. See Taco X-Pump Block. See also, Taco Solar X-Pump Block.

Zone Valve - In a hydronic central heating system, a device that controls the flow of system water to provide individual room or area comfort and energy savings. See, Taco Zone and Flow Control Valves.

Zoning Circulator - In a hydronic heating/cooling system, a circulator that controls the flow of system fluid to the various zones as the heating demand changes. See, Taco Priority Zoning Circulators.

Zone Valve Control - An electronic device that controls the zone valves in a hydronic central heating system. See, Taco Zone Valve Controls.

"00" Cartridge Circulators - The family of Taco circulators in which all moving parts are contained in a field-replaceable cartridge. Replacing the cartridge rebuilds the circulator, making Taco "00" Circulators extremely easy, fast and efficient. See, Taco "00" Circulators.