Gas condensing boiler replacement & installation guide

What are gas condensing boilers?   

By law, all boilers sold in the UK must now be condensing boilers. The difference between a condensing boiler and a  non-condensing boiler  is in the way in which the appliances utilise waste heat. In a non-condensing boiler, waste heat is exactly that - heat that is wasted. In a condensing boiler, however, the exhaust gases in the flue are put through a heat exchanger and the latent heat is extracted, rather than being released into the atmosphere. This makes condensing boilers at least 25 per cent more efficient than non-condensing boilers and allows new Viessmann boilers to achieve efficiencies of up to 98 per cent. Thanks to their efficiency, savings with a condensing boiler can be up to £310 compared to a non-condensing boiler, according to the Energy Saving Trust.

So, you’ve decided to get a new gas condensing boiler for your home. The next step is to get it fitted. The following condensing boiler installation guide should answer any questions you may have about this process.

Who can install a gas condensing boiler?

When it comes to gas boiler installation, by law these appliances must be installed by a Gas Safe registered engineer. The Gas Safe Register contains details of all gas engineers who are qualified and approved to work legally and safely on gas appliances.

When choosing an installer, you may wish to get a few quotes so you can select the most competitive one. You might also benefit from checking customer reviews before you make your final decision.

Your registered installer will make sure that your new appliance complies with all relevant building regulations and will provide you with documentation to prove this is the case. Make sure you keep these documents safe as you will need to provide them if you sell your home.

When should I get my boiler installed?

If you need to get a  new boiler  because your current one has broken down, you may not have a choice in terms of when you get your appliance installed. However, if you can be flexible when replacing your boiler, it’s usually best to get it installed during the spring or summer. Heating engineers may have more availability during these months, and because you won’t be as reliant on heating and hot water, the process should be as smooth and convenient as possible.

What happens during the installation?

Before your condensing boiler installation, your Gas Safe engineer will need to ask you a few questions so that they can prepare for the job. For example, they will want to know about the positioning of your boiler and flue, as well as how many radiators and bathrooms you have.

On the day itself, your engineer should bring all the materials they need to complete the task efficiently and safely. A good engineer will also make sure that they cover your surfaces and floors to protect them, and they will clean up after themselves once they have finished the installation.

If it’s a straightforward installation, the work should be completed within a day. However, more complicated jobs can take longer. For example, if you’re changing your boiler type or location, the process could take more than a day. Your engineer will be able to give you an accurate estimate of how long it will take before they start work.

It’s important to make sure you’re at home when the installation is complete so that your engineer can give you a run-through of the new controls. They should also provide you with a Building Regulations Certificate.

How much will a boiler installation cost?  

The cost of boiler installations varies depending on a range of factors, including whether you’re having a like-for-like switch with your existing appliance or going for a different type of boiler. The price will also be greater if you need to have additional pipework installed or you require a powerflush of your system.

To give you a very rough idea, replacing an existing combi boiler can cost around £600, while semi-replacing a conventional boiler can cost around £700. Installing a combi boiler in a new location may be approximately £1,100.

It’s a good idea to shop around, and make sure you get fixed price quotes upfront so that you know exactly what to expect.

How often should I get my boiler serviced?  

Once you’ve had a gas boiler replacement, it’s important to make sure you get your new appliance serviced on a regular basis in line with manufacturer instructions.

For the best possible performance and a long service life from your boiler, we recommend that you get your  boiler serviced  annually. However, if you are a landlord, servicing your boiler annually is not only recommended, it is a legal safety requirement.

By law, boiler servicing must be conducted by a Gas Safe registered engineer.

Why should I get my boiler serviced?

Scheduling regular services will help you to ensure your boiler is working as efficiently and effectively as possible, keeping your bills down and meaning your appliance lasts for longer. These checks also reduce the risk of inconvenient boiler breakdowns.

Servicing is also essential for safety purposes. During the checks, engineers can detect potentially dangerous carbon monoxide leaks.

As mentioned previously, if you are a landlord, it is also a legal requirement to get the boilers in your properties serviced every year.

What type of gas condensing boiler should I choose?

Before you arrange a condensing boiler replacement, you’ll need to be confident you’ve chosen the right appliance for your home. Condensing models are highly efficient, but which type of appliance would be best for you?

There are a range of issues to consider when making your decision, including how much hot water you use, how many bathrooms you have and how much space is available in your home.

Check out our guide to  choosing the right boiler.

If you’re not sure whether you could benefit from a new appliance, it’s worth asking yourself  is my current boiler energy efficient?

We hope this gas boiler installation guide has been helpful. If you have any further questions, don’t hesitate to contact our team