What is a condensing boiler and how does it work?

The benefits of a condensing boiler

One of the main benefits of a condensing boiler system is its ability to convert a high percentage of fuel into usable heat, leading to reduced energy waste, and consequently lowering energy bills, while keeping homes warm and comfortable.

By maximising energy usage, condensing boilers emit fewer greenhouse gases compared to non-condensing models. This reduction in emissions contributes to combating climate change and supports homeowners in cutting their own carbon footprint. 

Finally, condensing boiler systems operate efficiently at lower temperatures (typically around 60 degrees Celsius), making them a great option for modern heating systems like underfloor heating, without having to worry about the environmental implications.

The importance of a condensate drain and pipe in a condensing boiler

Boiler condensate is the acidic water produced when a high-efficiency condensing boiler extracts extra heat from the flue gases. This happens when water vapour in the exhaust cools down and condenses into a liquid, which is then drained away through a separate pipe. 

It is a product of modern, energy efficient boilers and is slightly acidic, with a pH similar to black coffee. To ensure a safe boiler operation, and maintain warranties, we always recommend having your boiler serviced regularly.

Optimal temperature settings for your condensing boiler

A condensing boiler’s optimal flow temperature to condense is around 60 degrees Celsius for a combi or combination boiler; or recommended 65 degrees Celsius for a system or heat only (conventional boiler) boilers – as heating systems with stored hot water need to ensure they are heating safely to avoid legionella growth in the cylinder or tank.

Boiler flow temperature is not room temperature; it simply means the temperature of the primary hot water around the central heating circuit. The hotter the flow temperature the quicker the radiators will heat up and the hotter they will feel to touch.

This is why setting the flow temperatures to 60 degrees Celsius for a combi (65 degrees Celsius for a system or heat only boiler) is recommended as it optimises condensing mode in a condensing boiler but also maintains a balance of comfort for your home. A thermostat in your home will maintain your comfort level setting accordingly turning on the boiler only when you need it, optimising fuel bills. Check out the Baxi range of controls here.

Hot water flow temperature is seasonal as the temperature of the incoming cold water from the mains will be colder in winter (requiring a higher hot water flow temperature) and warmer in winter (requiring a lower hot water flow temperature).