What is an open vented boiler and how do they work? Here we explain everything, without the jargon.
A vented boiler is one of the most common types of boilers you’ll find in domestic properties today.
But, if you’ve never had to fix or install a boiler or work on your heating system, it’s easy to get confused with all the different terminologies.
In this guide, we take a deep dive into understanding the vented boiler system, how it works, and what benefits it can offer compared to the other types of boilers.
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What Is A Vented Or An Open Vent Boiler?
You may be more familiar with the terms “regular” or “conventional” boiler. Well, open vent boilers, conventional boilers, and regular boilers are the same thing.
A vented or open vent boiler is one of the three most common types of boilers, the other two being combi and system boilers.
An open vent boiler has multiple units such as a cold storage tank and a hot water storage tank along with some other parts. The boiler comes in different variations as well.
Like all other boilers, an open vented boiler also has certain advantages and disadvantages and is more suitable for some properties while completely incompatible with others.
How Does An Open Vented System Work?
An open vent system has a cold water tank and a hot water tank, or a feed and expansion tank (F&E).
The cold water tank draws water from the mains and supplies it to the hot water tank or the F&E tank.
This F&E tank is located at the highest point in the system. Open vent systems work only with heat-only boilers.
The F&E tank heats the water and the tank expands as the water heats up. With an F&E tank, the increased water volume can be accommodated in the tank.
This system gets water from within the boiler and is thus a sealed system. So, if you use up the supply of hot water, you will have to wait for the tank to get more water.
The system is called an open vent because of the safety pipe that is located at the top of the heating system.
This pipe hooks over the heating system and releases excess pressure if the system is overheated.
Open Vent Boiler Set Up
Open vent boilers have a cold water storage tank. They are mostly kept in the attic and store water to be heated.
Most boilers also have a hot water tank, but some do not. The hot water tank stores the heated water, which is readily available when required.
Open vent boilers use radiators or other heat emitters for heating. The storage tank extracts water from the mains, and if there is a hot water tank, the heated water will be stored in the cylinder.
Although these boilers can be installed without a hot water cylinder, almost 90% of the boilers do have a hot water cylinder.
Advantages Of An Open Vent Boiler
Open vent boilers were the preferred boilers before the introduction of combi boilers in the 1980s.
There are still many homes that have an open vent boiler as they are more suitable for some properties.
Some of the advantages of an open vent system are:
With few devices and fittings compared to closed vent systems, the boiler is easy to operate.
They have lower maintenance costs.
They work with older radiators.
If you previously had an open vent system, replacing it with the same type is more cost-effective than replacing it with a different type of boiler.
If the mains supply is cut off, you still have access to hot water.
Disadvantage Of An Open Vent Boiler
While the boiler has its set of advantages, it also has a number of disadvantages, which is why they are being replaced with the more popular combi boilers.
Some of the disadvantages are:
Less energy efficient. A lot of heat is lost via the F&E tank, resulting in significant energy loss through the flue gasses.
Too many parts.
Space consuming.
Work only with heat-only boilers.
Accumulation of debris via the F&E tank.
Less cost-efficient.
What Types of Homes Use Open Vent Boiler Systems?
An open vent system has multiple parts and takes up a lot of space, making them better suited for larger properties.
For houses that have a high hot water requirement in multiple bathrooms at the same time, an open vent boiler system is the preferred choice.
This is because this system has a storage tank as well as a hot water cylinder, so the water can be made available in multiple bathrooms simultaneously. This is not possible with combi boilers.
Open vent boilers can be easily fitted in the attic, basement, or other storage space in larger homes.
You also need to consider your domestic hot water demands, the size of your property, and cost factors when determining whether an open vent boiler would be the best choice for you.
Today, you will also find open vent systems that are compatible with solar thermal technology.
This allows you to save energy, reduce costs, as well as reduce carbon emissions and do your bit for the environment.
Other Types Of Boilers
If an open vent system is not the right choice for your property or you’re thinking of upgrading to a new boiler, there are a few choices available in the market that you may like to explore.
Combi Boilers
Combi boilers are perhaps the most popular boilers and have replaced many regular and system boilers since they were introduced.
These are compact boilers that do not take up much space. Since there are no separate hot water and cold water storage tanks, no heat is lost when storing hot water.
In a combi boiler, the system reuses the energy from the flue gasses which makes the boiler more energy-efficient.
The water is also heated at the source only when needed. This has an advantage as well as disadvantages.
Since the water is heated as required, there is no energy wastage in storing and maintaining hot water.
However, as the water is heated on demand, you do not have access to pre-heated water which can become an issue if the main water supply is cut off. A combi boiler also cannot supply hot water to multiple bathrooms at the same time.
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System Boilers
They are similar to open vent systems as they have a hot water storage tank. However, system boilers do not have a cold water storage tank and water is used directly from the mains water supply.
System boilers are not only more energy efficient but also require less space compared to regular boilers, making them an ideal choice if you want to switch from a regular boiler.
What Are The Advantages Of An Unvented System
Having a combi or a system boiler has its advantages. Some of them are:
With no tank requirement or a single tank requirement, these boilers are more space efficient than open-vent boilers.
They generally provide stronger water pressure.
Without a tank, the risk of the water freezing or being contaminated is highly reduced.
While combi boilers are a preferred choice. An open vent system is a better option if your pipework is underground or old.
Open Vent Boilers Conclusion
There are two types of boiler systems — vented and unvented. While vented boilers used to be more popular, the advent of combi boilers has diminished their popularity.
Most people prefer the combi system as they consume less space and are more energy-efficient and cost-efficient and compatible with small and medium apartments.
Despite these advantages, if you have a large property and need to have a hot water supply in multiple bathrooms, an open vent system would still be the best choice.
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