Balanced Flue - inclined or horizontal?

[DavyJones]

Hello all,
I've a query regarding the fitting of a boiler's balanced flue.
It's been installed for several years but due to driving rain in the last month, I've had an issue of rain water getting into the combustion chamber of the boiler via the outer (air supply) section of the concentric (co-axial) flue.
As a result I've only just noticed that the flue is sloping downwards from where it comes through the wall towards the boiler (about 1cm in 50cm) therefore any water getting into it will run down into the boiler.
Common sense tells me it that if anything, it should slope very slightly in the opposite way.
In my case, it's in the garage and the flue only penetrates a single leaf wall, however, if this install had been through a cavity wall, it'd effectively provide a downward sloping bridge across the cavity (I always understood that if anything bridged the cavity it should slope downwards from inside to out to prevent water/damp creep).
Can anyone confirm that this is wrong (it'll be a fairly simple matter to realign it to horizontal, although more difficult to reverse the slope).
Davy

 

[Howsie]

You shouldn't touch the flu unless you're GSR I'm afraid. But if it's a condensing boiler the chances are it should slope toward the boiler. The clue is in the name, condensing.

 

[DavyJones]

Thaks Howsie, fully understand the GasSafe requirement, but surely an arrangement that permits ingress of water (at least a cupfull), some of which found it's way to the electronics board via the ignitor wire grommet, can't be right, or can it?
And re. my comment about bridging the cavity, surely that contravenes building reg's?
Davy

 

[Howsie]

If its a condensing boiler then they are designed for water to run in to then then out of the condense pipe. I've you've got water anywhere else then you've got a problem which needs looking at.

 

[Howsie]

The flu instructions for the boiler will clarify it for you.

 

[AWheating]

yes which is why condensing flues and there terminals are designed to have a slight rise to outside and keep rain out. (some have a fall built into the flue) We constantly discuss the sealing up of the gap between a flue and the wall it passes through and wether the dress guard is enough of a seal. One more reason to seal up correctly with sand and cement or whatever is to avoid damp/water ingress.

no condensing concentric flues should normally be fitted with a slight fall to outside following manufactures instructions of course.]

 

[DavyJones]

Hi again,
It's not a condensing boiler, just a combi. I assume AWheating meant "Non-condensing .... should have a fall to outside"? If so, that should apply to my system.
The water isn't getting in via the wall/flue joint, that's sealed OK. It's running along inside the flue.
There are no leaks anywhere that would cause this, it's definitely rainwater driven into the flue.
Neither the installation manual nor any of the others I've downloaded for other types mention any sort of incline.
Davy

 

[R1CKY]

Are you sure it is not a condensing boiler? You say it has been installed for several years, how much do you class as several, as condensing boilers have been compulsory since 2005 (bar a few rare exceptions).

Unfortunately some boilers suffer with rain water making its way in to the flue. If it is a condensing boiler, it must rise away from the boiler, otherwise condensation will run out of the flue and eat its way through your patio/kill your lawn etc.

If it is non condensing, consult a Gas Safe registered plumber to see about changing the flue angle, or maybe even the location of termination if driving rain is an issue.

 

[tamz]

Newer condensing boilers have to slope back to allow the acidic condensate to drain back to the boiler. Some flues have a built in slope and others don't. Unfortunately this slope also drains any driving rain back to the inside of the boiler (where the parts are) via the air duct .
When fitting in a cavity wall you are supposed to tie a drip wire around the flue in the cavity. I have never ever seen this done.

Older non condensing boiler flues should have a slight fall to outside.

 

[michael c]

Newer condensing boilers have to slope back to allow the acidic condensate to drain back to the boiler. Some flues have a built in slope and others don't. Unfortunately this slope also drains any driving rain back to the inside of the boiler (where the parts are) via the air duct .
When fitting in a cavity wall you are supposed to tie a drip wire around the flue in the cavity. I have never ever seen this done.

Older non condensing boiler flues should have a slight fall to outside.

I havent even heard of a drip wire tamz?

 

[stoker122]

I think Potterton used to supply a rubber ring to put on the flue in the cavity for this.
I think it was either the profile or Suprima.

 

[tamz]

I havent even heard of a drip wire tamz?

Like this

 

[tamz]

I think Potterton used to supply a rubber ring to put on the flue in the cavity for this.
I think it was either the profile or Suprima.

Profiles and Prima e's i think

 

[AWheating]

yes potterton did supply one with some flues.

 

[snowhead]

some of which found it's way to the electronics board via the ignitor wire grommet, can't be right, or can it?

No, there's something wrong with the grommet or fitting of the wire in it.

 

[DavyJones]

OK, I'm happy with the idea of a drip-wire/cavity gasket on condensing types through cavity walls.

Mine's a Worcester RSF280 Combi', installed about(?) 12 years ago by a Corgi engineer (OK, that's more than "several" years, but it doesn't seem that long). Definitely NOT a condensing unit.
The "fault" with the grommet was 'cos there was a short ptfe sleeve around the spark ignitor wire where it went thru' the gland/grommet. The gland was gripping the sleeve, however the sleeve was a loose fit on the wire and the gland wasn't compressing the sleeve onto the wire. The accumulated water lying in the bottom of the chamber was deep enough to flow into the top of the sleeve and run down the wire (which I could observe happening after unclipping the front panel).
That's how it was supplied; to my knowledge it's never been changed or tampered with.
As said previously, all work done by qualified engineers.
The question was posed here because an acquaintance (unqualified but sometimes assists a self employed GS engineer in installing systems) stated ALL flues should slope into the boiler, he made no distinction between basic combi's or condensing and he couldn't say why this should be, his view is probably understandable as he's probably only ever helped with installing condensing types.
I'll get in touch with someone who can correct the alignment.
Thanks for all the help.
Davy

 

[AWheating]

not been serviced in 12 years then?

 

[DavyJones]

Of course it has, that's what's worrying; none of the corgi of laterly,GS engineers picked up on either the sloping flue or the loose wire/sleeve.