dripping condenser flue

[JohnD]

I was looking at the horizontal flue today, to see if it was steaming in the cold weather, and noticed it is dripping.

it looks from the ground (5 metres below) as if the inner part has a slope, because I can see the inner terminal is not centralised, but higher than the outer tube. The boiler was fitted quite recently and is a Vitodens 100 Compact.

I can't reach it without a ladder, but I can reach the internal part of the concentric flue inside the kitchen.

I am guessing that, if it drips, it must have insufficient fall back to the boiler. and needs to be refitted at a bit more of an angle. The pipe has a sort of rubber grommett so I can't see the inside or outside hole in the wall and if it has any slack.

Is there more to it?

 

[fizzput]

Flue only needs about a 3 degree fall, so not much,

It's possible the condesate pipe (white about 3/4 inch diameter) is backing up...not so familiar with the boiler, but you can check the installation of this pipe and ensure it has no rise in it anywhere.

Can check the condesate trap inside the boiler to see how full it is....taking the cover off a boiler is for competent people only tho as per gas regs..

 

[JohnD]

the flue comes out the top of the burner enclosure, and the condensate hose is somewhere at the bottom, so I don't believe it can be backing up (the combustion chamber would probably be full of water)

The condensate hose comes straight out the bottom of the case, and runs pretty well vertically less than a metre to the standpipe (the boiler is fitted adjacent to the plumbing duct)

 

[fizzput]

I hear what your saying but it doen't quite work that way....i have seen this fault and that was what the problem was.

However appreciate your situation is probably quite diffferent (aren't they always )

 

[cowboyplumber]

Viessmanns drip. End of. Tough.

 

[JohnD]

 

[fizzput]

I think he's saying it's normal for a viessmann to drip so don't worry

 

[JohnD]

but is that true?

And is it acceptable?

 

[Agile]

This is a little questionable!

The flue has an inbuilt slope of about 3°.

However the instructions say fit the flue to a 3° slope.

A very competent Viessmann service engineer told me that they should be fitted with the outer of the flue level.

Get your ladder and inspect the exact profile of the inner part and make sure there are no casting misformations.

As suggested, Viessmanns do have a reputation for dripping a little.

Tony

 

[JohnD]

Get your ladder and inspect the exact profile of the inner part and make sure there are no casting misformations.

not really keen on hopping up a ladder

but I can put a small level on the indoors part of the flue, if that helps.

I also have the offcut from where it was shortened.

Why are the bloody things prone to dripping, though?

 

[Agile]

The exhaust gasses are probably exiting at a velocity of about 1m/sec and obviously they will exert some drag on the water droplets which might form there.

Tony

 

[JohnD]

are they more drippy than others, then?

 

[Agile]

They are thought to be more drippy.

The exit part seems to be rather smaller crossection than some and perhaps this results in a higher exit velocity than some other boilers?

Tony

 

[JohnD]