New boiler install - twin flue system - opinions please

[straso]

Hi all - looking for some advice/guidance please. Living in a 1 bedroom/1 bathroom flat which has a twin flue system and a current Keston boiler (boiler installed in 2009 and has recently stopped working). Have had many different quotes from different providers and they are all saying something different - majority have said to replace with a Keston/Ideal boiler even though I am wary on their reviews but the current one seems to have worked OK, however they don't seem to suggest any other brands (are there any?). In addition, some are suggesting the flues need replacing alongside installing a new boiler and others saying flues do not need replacing and can connect to the new boiler. From what I have read, the flues should always been changed when installing a new boiler, especially if older than 10 years - is this true?

Some people in the flat block have said they have changed their twin flue system to one flue system but no provider has suggested doing that and to stay with twin.

Let me know if you have any additional questions.

Many thanks!

 

[vulcancontinental]

Gas Safe guidance is change the flue system when changing the appliance.

If you are considering reusing the flue it should last the lifetime of the new appliance.

Your flue is 13 years old, change it.

You can certainly use a single flue system, called concentric (the flue tube is inside the air tube) but length may be a problem as twin systems can be run for greater distances. For example 6 metres total length 100/60mm concentric flue. 20 metres 125/80mm concentric flue. 20 metres each for separate flue and air tubes.

Also look for a boiler with a good modulation ratio. Assuming it is a combination boiler the hot water will require a high output, typically 25 to 30kW but the heating output in a small flat is probably less than 5kW. Look for a boiler that can have its heating output range rated (restricted to match more closely the actual heating requirement of the property) as this avoids cycling inefficiencies.

 

[straso]

Thanks - very helpful