Boiler Flue Specs

[Ginty]

Hi All,

I am getting a baxi 105e combi installed with a vertical flue through the roof.

I have a problem because the guy fitting the end terminal to the roof has made a bit of an arse of it and has it about 5 feet away from where I intended it.

This means that there's going to be a lot more ducting required than I had originally thought, and it looks as though it will exceed the guidelines in the baxi spec.

In summary the max flue length is 4m with every 90 degree bend accounting for a metre. I will need 2 bends and at least 3m of ducting which adds up to about 4m.

Now the roofer is adamant that the terminal can't be fitted where I want it (I'm on a top floor flat and he says to get it where I intend will mean getting a scaffold which = £££). However he is also adamant that he has seen these things fitted with

2-core flexible ducting, which with the lack of 90 degree bends, would probably be ok and just be slightly over the 4m limit.

So in the baxi literature there is no mention of flexible ducting. Is this a recognised and reliable way of venting a combi? And if so will it matter if I'm a bit over the 4m spec - how much tolerance is built into this spec?

If this is ok then are the flue kits supplied by the boiler manufacturers a bit of a rip off - presumably this flexible ducting will cost me a lot less than the various bits and pieces that make up the baxi kit.

Thanks a lot guys for your advice.

Cheers, Ginty

[Ed Sirett]

He should not be fitted flues to gas appliances without a CORGI card (or maybe working under close supervision of someone who is regsitered). Check him out. I have not seen the product which he talks of - it would have to be approved or made by the manufacturer for this application - I strongly doubt that it exists - although there is a chance I might be wrong.

Manufacturers know that you have no choice but to buy the flue accessories they make and the margins reflect this. When whoever planned this work hopefully took account of the flueing difficulties when estimating the job? Yeah right. Anyone who flouts the manufacturers rules will find themselves in substantial trouble if their work is inspected by CORGI. Which you can request if they do not cooperate.

This boiler does seem to have a rather restricted maximum equivalent flue length.

[Christian McArdle]

I don't know about the Baxi, but the Worcestor Greenstar has a choice of two flues, 100mm and 125mm. The 100mm has around 4m length (depends on horizontal vs vertical) and the 125mm has around 13m max length. Maybe the Baxi has a similar choice.

Christian.

[Ginty]

Yeah the baxi equivalent is a twin flue system - two 80mm flues, one exhaust and one intake from the boiler to the terminal. I really don't want to go this route for the sake of going an extra metre unless I have to.

The Worcestor one sounds a lot more practical and probably lighter on the pocket. I really didn't consider flue systems when I selected my boiler - it will certainly be a selection criteria next time though.