Combi boiler - maximum vertical flue length ?

[Mike Rogers]

I live in a town house and my combi boiler is located on the ground floor.

It is not a condenser and needs replacing.

As condensing boilers create much more visible steam I want to replace the boiler with one where a vertical flue can be taken straight up a dry riser to exit through the roof tiles. This would require a flue of around 24feet in length. Recently a gas fitter told me that this was far too long for a flue and that no boilers on the market were designed for such a long flue. Is this right? I am stuck in a difficult place, I need to replace the boiler, but if the flue stays in the same place this will annoy my neighbours; its not practical to move it to another location in the ground floor and too expensive and disruptive to move it to the loft.

Can anyone point me in the direction of boilers which would allow such a long flue?

 

[vulcancontinental]

There are many. The company I work for, Vokera, any of our boilers can have long vertical or horizontal flues, in some instances up to 50metres and I'm told a newer system up to 80metres but that's not confirmed.

I think you'd be looking for a 125mm concentric flue (the exhaust pipe run inside the incoming combustion air duct which on most of ours will run to a maximum length of 20metres(60').

The maximum length of any flue has to be reduced in relation to the number of bends in the run.

If you need longer you'd be looking at a parallel flue system - on ours two 80mm pipes from the boiler which joint into one terminal in the roofspace.

Get another gas engineer.

 

[Dan Robinson]

As VC has said, there are alternatives, and Vokera have plenty of options.

 

[Agile]

I am not sure if its still in production but Baxi brought out a back boiler replacement for their old Bermuda 552 a few years ago. But it was a heat only and not a combi.

This had a flexible plastic coaxial flue which was designed to run inside a chimney in a typical UK semi detached.

It also included a condensate pump which could pump up to 3m if required.

They kindly gave me a preview at Leamington before they showed it to their reps!

Tony