In the past, non-condensing boilers were a staple feature in many homes across the UK. However, thanks to advances in technology and changes to the law, these appliances have now been superseded by condensing designs. Condensing boilers are much more energy efficient than non-condensing models, meaning they can help households to significantly lower their energy bills and cut their carbon footprints. 

Keep reading to find out more about the differences between these two types of boiler, and whether it’s still possible to buy non-condensing designs.

Can You Still Buy Non-Condensing Boilers?

It’s essential to be aware that draining or flushing a combi boiler isn’t something you should attempt yourself unless you have the relevant knowledge and skills to do so properly and safely. If you try do this without the required know-how, you could damage your heating system and potentially your home too. It is also likely that you will invalidate your warranty.

Here, we take a look at the steps involved in these processes. We also offer advice on how to repressurise your combi boiler, and explain how cutting off your mains water supply can affect this appliance.

What is the difference between condensing and non-condensing boilers?

All well designed and maintained boilers burn their fuel efficiently, but traditional models inevitably lose heat in the form of hot gases that escape up the flue. This limits their overall efficiency. In contrast, condensing boilers have been designed to minimise this heat loss. They feature larger heat exchangers that cool the flue gases before they escape, condensing the water vapour out of them. The temperature of the flue gases during this heat exchange process drops rapidly from approximately 130℃ to 50℃. The condensation formed as a result is what gives the boilers their name, and there can be as much as two litres of it produced every hour. This condensate liquid is drained into a waste water outlet via a condensate pipe.

Thanks to this additional heat exchange process, condensing boilers are able to extract virtually all of the heat latent in the flue gases. This additional heat energy is then transferred back into the heating system. Typically, condensing boilers are more than 90 per cent efficient. For example, our condensing boilers are at least 98 per cent efficient. In contrast, non-condensing models may only have an efficiency rating of 70 to 80 per cent, while in old models this figure could be even lower at 50 to 60 per cent.

The extra efficiency of condensing boilers means they can offer major cost savings and they are also more environmentally friendly, helping you to lower the carbon emissions of your household. And these aren’t the only benefits. Condensing models also tend to be safer. Whereas non-condensing designs, often known as open vent boilers, typically take in air from inside the room, condensing boilers are completely sealed for heat insulation and they take their air from the outside. This means there is a lower risk of anything being sucked into condensing boilers.

When did condensing boilers become law?

Dating from 1st April 2005, all new gas boilers fitted in the UK are required to be condensing models. The same rule came into effect for oil boilers on April 1st 2007. The regulations state that all new boilers installed in domestic properties must be high-efficiency condensing designs.

This change in legislation was driven by the then Office of the Deputy Prime Minister and it was designed to make homes more energy efficient by dramatically reducing the emission of greenhouse gases.

In April 2018, there were further updates to the rules regarding new boilers. Under the Boiler Plus regulations, all new boilers in England must have an Energy-Related Products (ErP) rating of 92 per cent or higher. These rules also require all new oil and gas boilers to have a thermostat and programme timer. In addition, all new combi boilers must include one extra energy saving measure. This could be any of the following:

Flue gas heat recovery system

This system is designed to reuse heat generated by your boiler. In many cases, this technology is already built into new boilers, so doesn’t come with any additional cost.

Looking to replace your gas boiler?

Load compensating thermostat

This type of thermostat adjusts the temperature of your radiators in accordance with how warm your home is. When your home is cold, it will make your radiators hotter, and when your home is approaching the desired temperature, it will make them cooler.

Weather compensating thermostat

This technology is similar to a load compensating thermostat, but it adjusts the temperature of your radiators based on the outside temperature.

Smart thermostat

These thermostats enable you to control your heating system via your smartphone or tablet, even when you’re away from your home. They offer many of the same functions as a programmable thermostat.

If you’re not sure which additional energy saving feature is best for your home, you can ask your heating engineer for advice.

Do all new boilers have to be condensing?

Because of the building regulations now in place, the vast majority of new gas and oil boilers have to be condensing models. However, there are occasional exceptions to this rule. In rare cases, a condensing boiler may not be a viable option in a particular property. If an assessment carried out by a Gas Safe registered installer suggests this is the case in your home, you may be permitted to get an alternative system.

How do I know which new condensing boiler is right for me?

There are many different condensing boilers available. For example, you can choose between different types of boiler, such as combi or system designs, and there are a variety of sizes available too. You can also get models that are compatible with solar technology, helping you to reduce your bills and your carbon footprint even further.

Deciding which solution is right for your home can be difficult. You’ll need to take a range of factors into account, including the layout and size of your home and your heating and hot water needs. Fortunately, there is help available. You can research your options online. For example, you may find this article useful to help you decide what size of boiler you need for your home. For extra information and advice, you can speak to a heating engineer. They will be able to advise you on your options and help you to make an informed decision. 

Get a free consultation on a new heating system.

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