Understanding Heating Elements

Whether you are brewing a morning cuppa, running a load of whites through the wash, or needing hot water for a shower, you depend on a fundamental piece of engineering. So, how do heating elements work?

The magic behind these modern conveniences is the humble heating element. It is the hidden powerhouse inside countless household and commercial devices, seamlessly transforming raw electricity into reliable heating.

But how do these vital components actually function? In this guide, we will look at the science behind them. We will also discuss the special materials that make them last longer and how they work in different devices.

We also cover troubleshooting common faults, so you know what to do when an appliance goes cold.

The Science

Turning Electricity into Heat

To understand how these components operate, we must look at how the thermal energy is produced.

Also known as Joule Heating, this principle explains how electrical energy is converted to thermal energy. When an electric current passes through a conductor, the moving electrons collide with the atoms within the conductor material and encounter resistance. The resistance causes an atomic-level friction, which results in the material heating rapidly.

The core of a tubular heating element contains a resistance wire, usually made from nickel-chrome composition. There are many different diameter sizes of this wire to provide different levels of resistance. The narrower the path for the current, the higher resistance. If this flow of energy is localised in a small space, like a wire, it has nowhere to go but outwards as thermal energy. Due to the high resistance within the wire, the heat builds until it glows red hot… and we have a heating element!

Some applications may stop there with open wire coils as their heating element. However, most common practice is to insulate the coil in protective material. Tubular Heating Elements for example, we will insulate the coiled resistance wire in magnesium oxide powder surrounded by a protective metal sheath.

Ohms Law

Resistance is the constant to which a voltage is applied to. A heating element with the same resistance can be identified as many different wattages when ran on different voltage.

What Makes a Good Heating Element?

Not all metals can withstand being repeatedly heated to extreme temperatures. Designing a robust element means choosing the right component materials.

The Core Wire

As previously mentioned, the core resistance wire is typically a nickel chromium composition. Designed to withstand operating temperatures up to 1200°C whilst resisting oxidation.

Insulation and Sheathing

Exposed live electrical wires are incredibly dangerous. To ensure absolute safety, particularly in liquid-heating applications, the resistive wire is permanently encased in a protective metal sheath.

Between the live central wire and this outer casing lies a crucial safety barrier. Engineers rely heavily on the remarkable insulating properties of magnesium oxide powder. This heavily compacted mineral powder is an exceptionally good conductor of heat but a terrible conductor of electricity. It ensures the outer casing gets scalding hot without electrocuting the user or short-circuiting the water tank.

Regarding the outer sheath / metal casing, copper vs stainless steel durability is a key consideration. Copper conducts heat very well and is often used in domestic water tanks. However, it can be damaged by hard water over time. Stainless steel, whilst slightly slower to transfer thermal energy initially, offers superior longevity and resists chemical degradation remarkably well.

Specialised Heating Technologies

Whilst tubular metal elements are the most common, alternative styles exist for specific consumer needs. For instance, if you are looking into patio heaters or specialised cooking equipment, you might evaluate ceramic versus quartz infrared units. Ceramic elements heat up rather slowly but retain their warmth for an extended period, emitting a gentle, steady ambient heat. Quartz units, conversely, heat up almost instantaneously, providing highly targeted, directional infrared radiation that warms people and objects directly rather than heating the surrounding air.

Common Applications

1. Water Heaters

In standard hot water cylinders, the heating element for water heater systems sits completely submerged with direct contact to the water. They are a reliable tool for efficient water heating in homes, allowing for hot water on demand. Many domestic immersion heaters come with safety cut out thermostats in to prevent overheating.

2. Oven Heaters

For domestic ovens, a few different types of heating elements can be build in. At the top of the oven and visible to the user, is the grill element. This glows red when in operation to use intense and direct heat to cook the food.

Towards the back of the oven is the fan, surrounded by a circular heating element. When in operation, the fan continuously blows hot air which circulates around the oven and the food.

Some ovens have a bottom oven element at the base. This is used as a heat source for baking and roasting by warming the air inside the main cavity space. As the heat rises, the warm air circulates to cook the foods on the upper shelves.

3. Catering Appliances

Heating elements are also used in catering for hot cupboards, keeping cooked food warm before service or heat tableware for plating. A Bain Marie can use wet well elements to apply gentle and indirect heat to food. This is used to prevent burning, curdling, or splitting by keeping temperatures low and steady. Linking back to water heaters, often immersion heater elements are used as knife sterilisers in commercial kitchens for keeping utensils ready for safe food prepping.

Moving Up in Scale: Industrial Power

While heating elements play a role in standard households, they are a vital tool across many different commercial sectors. Industrial heaters offer heavy duty design and higher wattage output allowing for high demand in industrial applications. These robust components are engineered to deliver immense thermal energy in highly compact spaces, safely heating dense oils, harsh chemicals, or molten plastics where standard domestic elements would simply melt or fail.

Troubleshooting and Maintenance

All good things must come to an end, and like all hard-working components, heating elements will wear and fail.

Fault Finding

Once the heating element has been safely removed from the appliance and completely isolated from all power, first a visual inspection.

• Check the terminals for blackened or burnt spots.
• Check the sheath for any damage.

If the screen displays OL, this indicates there is an open circuit. This means that the internal wire is broken and a replacement heating element is needed.

Dealing with Burnouts

In larger forced-air heating systems, failure can be sudden and disruptive. You might wonder, what causes a heating element coil to burn out? Usually, the main culprit is what we call oxygen starvation. This can happen if the element is heavily insulated around the tube or the seal type is too restricting. If no air is getting to the element to carry the intense heat away fast enough, the internal wire overheats. It can ‘pop’ causing a hole in the heating element sheath, or if the sheath remains intact, the internal coil becomes brittle and grey causing snaps. This will cause an open circuit.

If this is a recurring issue with your heating element, it may be advisable to change the seal type to a more breathable high temp sealant or reduce the wattage.

Combating Limescale or Build-up

In hard water areas across the UK, mineral build-up is public enemy number one. Limescale thickly coats submersible elements, acting as an unwanted thermal insulator.

This severely restricts heat transfer, forcing the component to work much harder and eventually causing it to overheat and rupture. Not only does it reduce the lifespan of the element, but it also spikes your electricity bills.

Routine domestic maintenance, such as cleaning limescale off thermal components using specialised commercial descalers or standard white vinegar, can drastically extend the operational lifespan of your appliance and keep running costs manageable.

Knowing Heating Elements a Little Better

Now we have had a quick deep dive into heating elements and how they work, it is undeniable that they are a vital tool to everyday life. From the delicate, quick heating coils in a kitchen toaster to the robust heavy duty tank heaters heating oil for a production line.

By understanding exactly how they operate, you are better equipped to look after your heating elements in operation and knowing the right time to call us if it fails.