What is an Electric Heating Unit?

An electric heating unit, or an electric unit heater, is designed to warm up spaces and is available in various types suitable for a range of applications. The method of transforming electrical energy to heat energy is called electric heating. An electric heater converts electric currents to heat using an electrical resistor (heating element).

Workings of Electric Unit Heaters

An electric heat furnace operates just like a floor space heater. It comprises a heating element and a fan to divert the hot air into a specific area. The dimensions of the fan and heating element, as well as the inclusion of an evaporator coil, make an electric heat furnace. Its benefits are that operational failure seldom happens and it is simple to repair due to its user-friendly design.

Electric heaters need a minimum of 240V of electricity and a transformer enclosed in the heater reduces the power to 24V. It is then directed to the thermostat and further conveys the power from the red wire up to the white wire back to the furnace. This power busts the relays, permitting heat strips and fans to receive the current and initiate generating warm air into the space.

The fan plays an important role since it cools the heat strips in specified intervals to prevent them from overheating. A variety of processes for electric heating are resistance heating, electric arc heating, induction heating, and dielectric heating.

In certain cases, like arc welding, an electric current is given directly. For other methods, heat is generated inside the appliance. The heat created may be transmitted by conduction, convection, or radiation. Nichrome wire is placed as an active heating element entrusted by ceramic insulators. This is known as space heating for warming inside structures, for instance, in labs or confined areas where air handling is tedious. Certain reversed systems may be provided for the area to be kept around room temperature and warm air directed outside.

Types of Electric Heaters

Infrared Radiant Heaters

Electric infrared radiant heating occurs at very high temperatures where the heating element is enclosed in glass as well as a reflector to divert the output energy. It is useful for garages and basement levels.

Convection Unit Heaters and Fan-forced Convection Heaters

Convection unit heaters use thermal conduction, which takes place when the heating element warms the air and it rises due to its lower density and buoyancy, and the cold air fills up the space. The continuous cycle of warm air rising and cool air taking its place is termed convection. These heaters are fit for an enclosed area.

Fan-forced convection heaters are similar to convection (cooling effect) heaters, but the installation of an electric fan makes them stand out when compared to other electric heating units. The flow of air becomes faster with noise and a threat of ignition. These heaters are made for natural convection but with an increased air flow rate. They are compact and cost-efficient for tiny room heating systems.

Storage Heating

Storage heating captures heat inside bricks made of clay and releases it during the day. This kind of heater system produces less expensive electricity bills, and modern prototypes contain a thermostat/sensor for high efficiency and measurement of the room temperature.

Immersion Heaters

Immersion heaters consist of an electric resistance heating element in a tube and kept inside water for heating purposes. The element may either be encased in a metal pipe to prevent corrosion or placed openly in the liquid. These heaters don’t require any control thermostat, as they are created to be used for a short duration. Applications include electric showers, domestic heaters, and heaters with no tanks.

Circulation Heaters

Circulation heaters are also called Direct Electric Heat Exchangers (DEHE). In this type of heater, the installation of the heating element occurs inside a shell side to produce the effect of heating directly. One of the merits is that these heaters are 100% efficient. They are used for boiling liquids and heating gasses (gas furnaces), especially in industrial processes.

Other types of electric heating units include explosion-proof heaters, gas furnaces or gas-fired heaters, wall heaters or wall-mounted heaters, and so on.

Lighting System and Heat Pumps

Lighting systems are combined with heating, ventilation, and air conditioning (HVAC) systems inside huge commercial towers. The unused heat from fluorescent lamps is trapped inside the air coming back from the heating system. It is advisable to construct an energy-efficient system that generates a source for electric heating. 

Heat pumps capture a lesser grade of heat from outside. Installation of ground-source heat pumps is recommended in spaces having average temperatures below freezing, since these pumps have a greater efficiency as compared to the air-source heat pumps. Geothermal heat pumps provide low energy consumption (73%), whereas conventional electric resistance heating consumes much more power and energy.

Merits of Electric Unit Heaters

• Accurate temperature control and even distribution of heat energy.
• For the production of heat, combustion is not used.
• Capable of reaching temperatures that are unattainable in case of chemical combustion.
• Can be manufactured in many shapes and sizes, and can be placed anywhere within the space.

Demerits of Electric Unit Heaters

• Electrical energy is expensive, whereas fuel usage is less costly.
• The initial expense of heating apparatus and infrastructure is very high.

Context and Applications

General uses include space heating, cooking, water heating, and industrial processes. Electric motors are installed in heat pumps to absorb air from the outside and converge it to the area which needs warmth. The topic is studied in courses for degree programs such as:

• Bachelors in Mechanical Engineering
• Masters in Electronics and Telecommunication
• Masters in Electrical Engineering
• Masters in Industrial Engineering

Practice Problems

1. What is the full form of HVAC?

1. Heating, ventilation, and air-conditioning
2. Heating, viscosity, and air-conditioning
3. Heating, ventilation, and acoustics
4. Hammering, ventilation, and air-conditioning

Answer: a

Explanation: The full form of HVAC is heating, ventilation, and air-conditioning. These systems are installed inside huge commercial towers. The unused heat from fluorescent lamps is trapped inside the air coming back from the heating system.

2. Which type of heaters are used in garages and basements?

1. Gas furnace heaters
2. Heating elements
3. Infrared radiant heaters
4. Baseboard heaters

Answer: c

Explanation: Infrared radiant heaters are operated at very high temperatures where the heating element is enclosed in glass as well as a reflector to divert the output energy. They are used in garages and basements.

3. Which of the following statements is incorrect?

1. Circulation heaters are 100% efficient and are used for boiling liquids and heating gasses (gas furnaces), especially in industrial processes.
2. In some heaters, installation of the heating element is not required.
3. Capturing heat inside bricks made of clay and releasing it during the daytime is known as storage heating.
4. Geothermal heat pumps provide low energy consumption (73%), whereas conventional electric resistance heating consumes much more power and energy.

Answer: b

Explanation: In all heaters, the heating element is mandatory.

4. Which of the following is an active heating element?

1. Copper
2. Bitumen
3. Silver
4. Nichrome

Answer: d

Explanation: Nichrome is an active heating element entrusted by ceramic insulators.

5. What are the advantages of electric heating units?

1. Better efficiency
2. Able to provide unachievable temperatures
3. Manufactures in many shapes and sizes, which can be placed anywhere within the space
4. All of the above

Answer: d

Explanation: The advantages of electric heating units include better efficiency, the ability to provide unachievable temperatures, and manufacturing in many shapes and sizes, which can be placed anywhere within the space.

Related Concepts

• Power frequency heating
• Indirect and direct resistance heating
• High-frequency heating
• Electric arc furnace
• Induction furnace
• Muffle furnace