How Combi Boilers Work

Many people ask us what a Combi boiler does and if it saves money.  Below is a brief description.

A Combi boiler directly heats both Radiator water AND hot water (that comes from your taps) eradicating the need for a hot water storage tank in the airing cupboard.

The Hot water is heated directly when you open any hot tap in the system. This is achieved using a stainless steel direct heat exchanger with a massive capacity to transfer heat quickly from the boiler water (which no one would like to bath in!) to the clean, mains cold water that you want heated to come out of your taps.  Some boilers do have a heat ‘store’ of hot water. These vary in capacity but are never more that 15 litres.

In areas with very hard water and a high scale content, the heat exchanger can ‘fur up’ and water flow can slow. Some engineers change the heat exchanger but it can be cleaned. Remove it from your boiler and leave in a bucket of limescale remover and then rinse thoroughly.

Money is saved because you do not need to heat a 100litre+ tank of hot water throughout the day and night. You only heat what you need, when you need it. Combi boilers today can supply 18 litres of water a minute at 35 Degrees making it suitable for flats and houses.

The diagram to the right shows how a combi boiler is usually installed. The cold feed enters the boiler, is heated in the heat exchanger and then passes out of the domestic hot water outlets when a hot tap is opened.

There is one small consideration. Should anything happen to the boiler (breakdown) you would be left with no heating and hot water. This is because there would be no hot water tank with an Electric Immersion to heat your water as a back-up. Thats something to keep in mind.combi boiler system installation

Combi boilers can be Condensing or Standard efficiency.

So we’ve had a quick look at how Combi boilers work. What if you’re looking to buy one? Most customers find it easier to allow their installation engineer to buy the boiler. Think again. If you buy the boiler and get the engineer to fix it for you, then you avoid their mark up and save money. If you aren’t sure which boiler to buy then ask your installing engineer what Kilowatt or BTU rating you will need and buy the boiler accordingly.

Buying boilers online is relatively simple. We found a few suppliers that deliver boilers next day.