Industrial & Commercial Power, Pumping & HVAC Solutions


Heater Basics and Glossary of Terms


Air Changes/Hour — the number of times per hour that the air in a room or building is changed by mechanical means.

BTU — the basic unit for measuring the output of a heater (acronym for British thermal unit). One BTU equals the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

Combustion — the chemical action of a substance with oxygen resulting in the evolution of heat and some light. The three requirements for combustion are sufficiently high temperatures, oxygen and fuel.

Conduction — the transmission of heat through and by matter.

Convection — the transmission of heat by the circulation of air.

Heat Exchanger — a device used to transfer heat from one medium to another. It allows fumes and the by-products of combustion to be vented away from the heated airflow in an indirect-fired heater.

Heat Rise — the desired rise in temperature in degrees Fahrenheit for a heated area. To determine heat rise, subtract the outside temperature from the desired inside temperature in the area being heated.

Resistance Heating — heat generated by electric current passing through a resistance wire. This is the most common type of electric portable heater.

Static Pressure—the pressure which tends to burst a pipe. It is used to overcome the frictional resistance to flow through the pipe. It is usually expressed in inches of water column.

Therm — a unit of heat equal to 100,000 BTUs. It is also used to measure natural gas and as a basis for comparing different fuel types. One therm equals 40 cu. ft. of natural gas.

Thermostat — a device that automatically responds to temperature changes and activates switches controlling heaters and other HVAC equipment.

Heater Types & Uses

Forced Air Heaters utilize a fan or blower to create artificial air movement, which removes the heat from the heater surface very quickly. Forced air heaters can circulate heated air over very long distances and are usually the choice for heating larger areas. Forced air heaters are available in direct-fired, indirect-fired and electric types.

Direct-Fired Heaters are ideal for applications where a great deal of heat is required in non-enclosed areas such as general construction, ventilated warehouses and parking garages. They are highly efficient since all the heat is transferred to the heated airflow. Direct-fired heaters are both compact and economical due to their simple design. They are available in oil, propane and dual fuel (propane and natural gas) types.

Indirect-Fired Heaters utilize a heat exchanger that keeps fumes and exhaust products out of the airflow, providing clean, dry, odorless heat. A flue vents excess moisture, carbon monoxide and other products of combustion. Indirect-fired heaters can also accommodate ductwork, which allows distribution of clean heated air to specific target areas. This feature allows placing the unit outside in a remote location from the area being heated. Indirect-fired heaters are available in oil and dual fuel (propane and natural gas) types.

Read about how our indirect-fired heaters can be used to kill the HPAI virus

Flameless Heaters produce heat from engine exhaust, the hydraulic system and heat exchangers inside the unit. The efficiencies of these units allow for less fuel consumption than comparable units. Due to zero combustion, flameless heaters eliminate the need for fire watch and are able to be placed in close proximity to hazardous areas. Ideal for hazardous projects in locations requiring a non-open flame heating source such as oil wells, chemical and power plants, coal facilities and refineries.

Convection Heaters transfer heat to the surrounding air by the natural circulation of air through the heater. Air motion is a result of gravitational forces where the heated air is lighter than the cooler air. Heated air rises from the top of the heater and is replaced by cooler air that enters from the bottom. Individual convection heaters are a common heat source for smaller enclosed areas and multiple units can be combined to heat larger areas.

Radiant (Infrared) Heaters heat people and objects rather than air or space. Radiant heat is less affected by drafts and large air movements, since it passes through the air to heat floors, walls, machinery and people. This makes radiant heaters ideal for outdoor and high ceiling heating applications. They are also ideal for spot heating areas like shipping docks; for protecting valves, pumps and machinery from freezing; and for thawing frozen pipes. Radiant heaters generate no noise, fumes or flames.

Electric Heaters provide clean, dry heat with none of the combustion by-products common to fossil fuel burning units. They are also very quiet and require almost no routine maintenance. Applications include general construction in enclosed areas, temporary commercial heating, special event tents and moisture control/drying. Electric heaters are available in portable and industrial types.

Fuel Types

Kerosene and Fuel Oil are by-products of petroleum refining and are comprised of liquid hydrocarbons. They are available in several grades depending upon the range of distillation. Kerosene and No. 1 fuel oil are recommended for oil heaters and have a heat rating as follows: 
1 gal. = 126,000 BTUs

Propane (LPG) consists of refined natural gases that are extracted in a liquid state during refining, under pressure. It remains in liquid state during storage and transportation. When the pressure is reduced, propane vaporizes and becomes a gaseous fuel. When stored in a tank, propane is in both liquid and gaseous state; one gallon of liquid propane weighs 4.35 lbs. and expands to 36.35 cu. ft. of gas when it is evaporated (at sea level). Heat ratings for propane are as follows:
1 gal. = 91,500 BTUs
1 lb. = 21,030 BTUs
1 cu. ft. = 2,521 BTUs

Natural Gas is the lightest of all petroleum products and is lighter than air. It remains in a gaseous state throughout the pressure and temperature changes that occur during distribution. Natural gas is sold by the therm, with one therm equal to 40 cu. ft. Heat ratings for natural gas are as follows:
1 therm = 100,000 BTUs
1 cu. ft. = 2,500 BTUs

Electricity is sold in kilowatt hours (kWH), with one kWH equivalent to 1,000 watts usage for one hour. Electric heaters utilize resistance heating, which converts electrical energy to heat at the rate of 3,450 BTUs per kilowatt (kW).

Calculating Heating Fuel Costs

Calculating Heating Requirements

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