What Is An Immersion Heater?
What Is An Immersion Heater?
An immersion heater is an electric heating element that is submerged inside a hot water cylinder or tank to heat water on demand. It functions by transforming electricity into heat, which is transferred efficiently to the surrounding liquid. Immersion heaters offer versatility in residential or commercial heating systems by acting as either the main source of heat or act as a back up if a boiler fails, ensuring a continuous supply. Not all houses have immersion heaters.
They are typically managed by a thermostat, which guarantees that the water safely reaches the required temperature and avoids overheating. Immersion heaters are adaptable and simple to install and they are available in both fixed and portable tank versions. Immersion heaters offer quick, reliable and energy efficient heating and are frequently found in tanks and water cylinders.
In this guide we will explain the benefits and drawbacks of immersion heaters, best practice for using them effectively and signs that your immersion heater is on for too long.
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Key takeaways
Use a thermostat or a timer - avoid leaving the heater on continuously to control heating and reduce electricity bills.
Insulate your hot water tank - adding a jacket can help retain heat, reduce energy waste if your cylinder is not already insulated.
Regular maintenance - to extend lifespan make sure that you descale the heating element, check the electrical connections and make sure you schedule annual inspections.
Spot problems early - your immersion heater may need attention if you get signs of overheating, high electricity bills or electrical trips.
How does an immersion heater work?
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Electricity is passed through a heating element inside the water tank to power an immersion heater
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This element heats up due to its resistance to the electrical current (a process known as Joule heating).
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The surrounding water immediately absorbs the heat produced.
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As the water heats up, warmer water rises to the top of the tank and cooler water sinks, creating natural circulation.
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The circulation helps to heat the entire tank evenly over time, ready to be supplied to your taps, bath or shower.
How long should immersion heaters be on for?
The time it takes to heat up a full tank of water will depend on the size of your tank, the kW rating of the immersion heater and the usage. An immersion heater with a higher kW rating will heat up water faster than one with a lower kW rating. For example, a 3kW heater will heat a tank significantly quicker than a 1kW heater.
Most immersion heaters in UK homes need to be on for 1.5 to 2.5 hours to heat a full tank of water. A tank that is between 80 and 120 litres should take anything from 1 to 1.5 hours, whereas a tank that is over 120 litres can take anything up to 2 or 2.5 hours.
Signs your immersion heater is on for too long
Below are some signs that you should look out for if your immersion heater has been on for too long.
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Noises from the tank - rumbling, hissing or loud bangs can imply that the water is being overheated.
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Constant hot water - meaning that there could be a fault with the thermostat.
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Frequent electrical trips - a malfunctioning thermostat or element could cause the heater to trip the circuit breaker.
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Rise in electricity bills - indicating that the immersion heater is on for longer than necessary leading to wasting energy and higher costs.
What are the benefits and drawbacks of immersion heaters?
Immersion heaters offer the option of boiler back up assistance in addition to efficient on demand water heating through an electric element in a cylinder. However, like any heating solution, they come with a mix of benefits and drawbacks, ranging from efficiency and cost effectiveness to convenience and adaptability. Below, we break down the main benefits and drawbacks.
Benefits
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With off-peak rates like economy 7, immersion heaters can heat water overnight for a cheaper price and the hot water will stay hot throughout the day as long as your hot water cylinder is insulated properly
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Immersion heaters are easy to use, they only require you to have a switch or a timer to regulate the temperature of the water. They don't rely on complex systems, making them easy for homeowners to operate without technical expertise.
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It supplies back up hot water if your main heating system malfunctions, meaning you are guaranteed hot water whenever you need it due to their independent operation.
Drawbacks
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You must heat the water to at least 60°c as the immersion heater needs to reach a safe temperature to eliminate bacteria.
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You can expect higher costs as immersion heaters are less economical as a major water heating technique since they use electricity, which is typically more expensive than gas.
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It is limited by tank capacity which means that it can run out of hot water if the tank runs out as it does not have on demand hot water like combi boilers, so you may have to wait for it to reheat before more is available.
Best practices for using an immersion heater effectively
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Choose the correct wattage for your tank to save energy and guarantee quicker heating and make sure that you get an immersion heater that is appropriate for the volume of your water
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Using a thermostat will save energy. As when the water reaches the desired temperature which is often 60°c the thermostat will automatically turn off the heater which avoids overheating and wasting electricity.
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Having a timer will allow you to save energy costs as you can enable the heater to run only when necessary or during less expensive off peak electricity periods such as economy 7 tariffs.
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Insulating your water tank is beneficial as the water will stay hotter for longer which means that you will save energy and reduce the running costs. Good insulation is also good as it will take less time to raise the water temperature when you switch the heater back on as there is less heat loss between uses.
Safety and maintenance tips for immersion heaters
It is critical to adhere to appropriate safety and maintenance procedures to guarantee long term performance and safe operations. Below are some tips that you should consider:
Safety
Installation - immersion heaters should always be installed by a qualified professional.
Avoid contact while powered - to avoid getting an electric shock you should never touch the heater whilst it is plugged in or heating water.
Plug directly into a suitable socket - avoid using extension leads.
Immersion heaters should not be on continuously - to safely regulate heating, use a timer or make sure the thermostat is operating properly.
Maintenance
Regular check for corrosion or damage - check if there are any signs of rust, spots or cracks as it can fail unexpectedly and become unsafe to use.
Regular cable inspection - look out for wear and tear on the power cord and plug and replace them if necessary.
Make sure it is stored in a dry place - making sure it is stored in a cool place to prevent moisture as this can lead to faults or rust.
A qualified professional should be scheduled annually - an inspection should be carried out to check the thermostat, inspect electrical connections for tightness and corrosion.