Understanding Heat Exchangers in Boilers: Importance, Types, Costs, and Maintenance in the UK

Living in the UK, you must be fond of heat exchangers. When you face boiler problems and get it inspected by a Gas Safe registered engineer, you may discover the issue was related to a faulty heat exchanger.

Due to the above reason, it is essential to understand what a heat exchanger is, its components, and how it plays a crucial role in the optimal functioning of your boiler.

This article will tell you what heat exchangers are, their importance, and how they work. In addition, we will also discuss its types, the cost of purchasing a new one, and tips to maintain it.

So read this article until the end to understand a heat exchanger and make an informed decision.

What is a heat exchanger?

As the name suggests, a heat exchanger is a device that facilitates heat exchange between two or more mediums. Its components are in the form of tubes, plates, and shells containing an internal fluid. As the fluid moves through the different surfaces, it transfers energy in a controlled manner.

Heat exchangers are integral to providing your home with heating and hot water. Apart from homes, they are also used in industrial settings such as heating and cooling systems, power generation facilities, sterilisation equipment, reactors, and evaporators.

Compatible with advanced technology, they are also found in vehicles. Vehicle heat exchangers are efficient devices that control temperature, save energy costs, and provide reliable operations.

What is a boiler heat exchanger?

As the name suggests, a heat exchanger in a boiler exchanges heat between two fluids without allowing them to encounter each other. A heat exchanger consists of a long, spiralling pipe through which cold water flows.

Heated gases are fed through the surface of the pipes, heating the surrounding water and pumping it through radiators to warm your home and provide hot water for your taps and showers.

How does a heat exchanger work in a boiler?

Essentially, a heat exchanger transfers the heat produced by a boiler burning natural gas, creating a grid of hot gases that flow through coiled pipes to heat the cold water passing through them. As the water passes through, it absorbs the heat, becoming warmer while the hot gases are cooled down.

Types of heat exchangers

1- Air Cooled Heat Exchangers

Air-cooled heat exchangers are essential in many industrial and commercial processes where high-temperature fluids (such as steam or hot oil) require cooling. These exchangers utilise air as the cooling medium, typically passing fins or blades of metal through an airstream to facilitate thermal transfer between the medium and process fluid.

They are reliable units that can be prefabricated to varying sizes and capacities, with designs that feature either bare or jacketed tube bundles for maximum efficiency. Air-cooled heat exchangers have applications in industries such as petrochemicals, food processing, and HVAC systems, where effective temperature control must occur quickly and efficiently across the whole system.

2- Shell and tube heat Exchangers

Shell and tube heat exchangers are one of the most commonly used process equipment in industrial operations, providing adequate heat transfer between two fluid streams. They consist of tubes within a sealed shell that allows for efficient counterflow between the two fluids, resulting in high thermal efficiency and effectiveness.

This type of heat exchanger can also be designed using various materials due to its versatility and compatibility with many chemicals, temperatures, and flow rates. Due to their appeal in terms of cost-efficiency, durability, corrosion resistance, and ease of maintenance, they have proven to be an integral part of numerous industries ranging from power generation plants to food processing establishments.

3- A plate heat exchanger

A plate heat exchanger provides efficient heat transfer through the help of joined metal plates in an enclosed frame. The plates are supported with gaskets that provide separate flow channels, ensuring they are kept separate and come into contact when needed to transfer heat.

The plate heat exchanger’s operating efficiency provides cost-effectiveness and flexibility regarding cooling, heating, condensing, and evaporation. Additionally, its large surface area and robust design provide capability for high- and low-pressure applications.

The heat exchanger in condensing and non-condensing boilers

The concept of heat exchangers in condensing and non-condensing systems is different, as each type has different numbers of heat exchangers. So, knowing how they work in condensing and non-condensing boilers is important.

Non-condensing boilers

Non-condensing boilers use a single heat exchanger, which extracts heat from the burned gases to heat the water. After the heat is transferred to the water, the waste gases are released through the exit flue, resulting in an increased carbon footprint.

Condensing boilers

In contrast, condensing boilers feature two heat exchangers: a primary heat exchanger and a secondary heat exchanger. The cold water enters the secondary heat exchanger, absorbing heat from the flue gases that would have been wasted in non-condensing boilers.

After being heated, the water is transferred to the primary heat exchanger, which further heats it before sending it to radiators and hot water tanks. The second heat exchanger makes a significant difference, absorbing more heat from the gas rather than releasing it into the atmosphere.

Type of material used for the manufacturing of a heat exchanger

The heat exchangers are manufactured with aluminium and stainless steel as raw materials. The reasons behind using aluminium are its low manufacturing cost, conductivity, and lightweight nature. On the other hand, stainless steel is used because of its corrosion resistance and compatibility with clean and plain water. Stainless steel also offers adaptability at high flow rates.

Symptoms of a faulty heat exchanger

Water leakage

If you detect leakage near your heat exchanger, one of its components is likely broken, or the heat exchanger has worn out and needs to be replaced. To determine the source of the leak, scrutinise the area. If you aren’t able to locate the source, it is recommended that you contact a Gas Safe Registered Engineer for assistance.

Strange noises

Your heat exchanger might make strange noises like banging or whistling if it has a lot of limescale and dirt. This causes blockage of the water flow and reduces the performance efficiency of the system, resulting in higher running costs.

Although, in some cases, the boiler makes noises because of the airlock in the radiator, that can be solved by bleeding out your radiators.

Irritating smell

When there is a crack in your heat exchanger, or it is damaged for any other reason, irritating odours similar to formaldehyde can be released, causing headaches and watery eyes. In this case, we strongly recommend that you turn off your central heating system and call a Gas Safe engineer immediately.

How to maintain the life and performance of your heat exchanger

Maintaining your heat exchanger is essential for the proper functioning of your central heating system. If not properly maintained, it can disrupt your home’s hot water supply and heating. Sludge and limescale are the primary causes of problems in your heat exchanger. We strongly advise against attempting to remove limescale and sludge yourself and instead recommend contacting a Gas Safe registered engineer to do so.

Additionally, they can install a filter to prevent future buildup. To remove sludge and debris, it is recommended that you get a central heating power flush every 4-5 years. These precautionary steps are essential for ensuring optimal heat exchanger performance and prolonging its life.

Replacement cost of a heat exchanger

If a heat exchanger has been fixed and maintained so often that it no longer works, it can be replaced. But replacing the heat exchanger can be expensive, costing between £500 and £600. If your boiler is more than 10–15 years old, it is recommended that you invest in a new boiler to avoid further repair costs.

Conclusion:

We hope you now understand the importance of a heat exchanger, how it works, what components it is composed of, and the signs suggesting it is damaged. Please do not attempt to repair it; it is a technical matter and should be left to the experts. You are also aware that repairing it can be costly, so if you are looking for a boiler replacement, please get in touch with us at 0345 3192 247 or contact us. We will be more than happy to help you find the perfect boiler that best suits your needs.

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