(horizontal) condensing boiler flue constantly dripping

slipstream

we recently installed a (viessmann vitodens) condensing boiler.

the builder is running the boiler to dry out plaster/paint etc. and as it runs there is a good amount of water dripping from the flue. i noticed this as the paving is always wet below the flue (see attached).

as far as i can tell the flue is perfectly horizontal (see attached) but all references i can find indicate that the flue should have a slope (3 degrees or 50mm/m).

should the flue have a slope and, if so, do you think it would reduce the amount of dripping much?

thanks for your help,

slip

rightjob!

slipstream wrote: »

we recently installed a (viessmann vitodens) condensing boiler.

the builder is running the boiler to dry out plaster/paint etc. and as it runs there is a good amount of water dripping from the flue. i noticed this as the paving is always wet below the flue (see attached).

as far as i can tell the flue is perfectly horizontal (see attached) but all references i can find indicate that the flue should have a slope (3 degrees or 50mm/m).

should the flue have a slope and, if so, do you think it would reduce the amount of dripping much?

thanks for your help,

slip

yes you should have a fall back to the boiler on the flue pipe.

you may still get some discharge water coming out of the flue but the amount you have is too much

Dtp1979

I'd also have a look at your flue clearances there. That's a very enclosed area. They would be a good chance of the flue gasses mixing with the air for combustion, resulting in high CO.

slipstream

rightjob! wrote: »

yes you should have a fall back to the boiler on the flue pipe.

you may still get some discharge water coming out of the flue but the amount you have is too much

should a 87 degree bend be used or would there be sufficient play in a 90 degree bend and pipes to create the slope?

Dtp1979

slipstream wrote: »

should a 87 degree bend be used or would there be sufficient play in a 90 degree bend and pipes to create the slope?

I think they come slightly off 90 but there's usually a little bit of play.
Was the boiler commissioned yet?

slipstream

Dtp1979 wrote: »

I think they come slightly off 90 but there's usually a little bit of play.
Was the boiler commissioned yet?

I'm not sure but I haven't got a cert yet. Should commissioning highlight the issue?

Dtp1979

slipstream wrote: »

I'm not sure but I haven't got a cert yet. Should commissioning highlight the issue?

You should get a cert 2. Absolutely insist on it. This will not fix the problem of dripping but highlight it to the installer. What commissioning will do is highlight any dangerous fumes emmiting from the flue due to re circulation of flue gasses.

rightjob!

slipstream wrote: »

should a 87 degree bend be used or would there be sufficient play in a 90 degree bend and pipes to create the slope?

there is a bit of play on the 90 bend to get the fall on them.

good advice from dtp1979 there.

it is very inclosed,a plume kit would take away the worries there.

slipstream

rightjob! wrote: »

there is a bit of play on the 90 bend to get the fall on them.

good advice from dtp1979 there.

it is very inclosed,a plume kit would take away the worries there.

Thanks for all your advice.

Should the plume kit extend the flue up above the passageway? I guess this would also solve the dripping issue.

Would adding a slope to the current flue be much work or cost? Raising the opening would be feasible at the moment as building is ongoing.

What does commissioning involve, who would do it and is it required for new boilers?

Wearb

I think that a simple bend ( perhaps 45°) on the end of your flue would sort you out. Installer would have to decide if it would do.
But I don't see a problem.
Perhaps some of the lads here might point out problems with my suggestion. So wait and see.

rightjob!

slipstream wrote: »

Thanks for all your advice.

Should the plume kit extend the flue up above the passageway? I guess this would also solve the dripping issue.

Would adding a slope to the current flue be much work or cost? Raising the opening would be feasible at the moment as building is ongoing.

What does commissioning involve, who would do it and is it required for new boilers?

yes with the plume kit you can re route the gases to a suitable location.

no its not the biggest job to do,just a bit of a pain seen as how its covered in around the flue now.

if the builder isnt wanting to do it you could always show him that the flu is leve and should have a fall on it.

is that silicone around the flu where it goes outside?!

slipstream

rightjob! wrote: »

is that silicone around the flu where it goes outside?!

I'm not sure what they used. What would be a suitable flue sealant?

rightjob!

slipstream wrote: »

I'm not sure what they used. What would be a suitable flue sealant?

sand and cement.

put a smaller level on the flu pipe,looks like its sitting on the collar of the elbow which makes it higher at the back.

slipstream

rightjob! wrote: »

sand and cement.

put a smaller level on the flu pipe,looks like its sitting on the collar of the elbow which makes it higher at the back.

i noticed that at the time and raised both ends the same amount but i will try with a smaller level in any case.

would you mind explaining the commissioning process (or pointing out where i can find out more about it)? what would be involved and would the installers usually also be the commissioners and certifiers? also what would the certificate look like?

slipstream

Wearb wrote: »

I think that a simple bend ( perhaps 45°) on the end of your flue would sort you out. Installer would have to decide if it would do.
But I don't see a problem.
Perhaps some of the lads here might point out problems with my suggestion. So wait and see.

i would need to measure but i'm not sure the flue terminal would fit if it was pointing 45° up.

Wearb

slipstream wrote: »

i would need to measure but i'm not sure the flue terminal would fit if it was pointing 45° up.

Judging by your spirit level, any little rise at the end would most likely sort you out. Even if that meant taking a saw to a bend to make it suit.
Maybe gouge out that silicone and stick a little wedge under it to rise it a little.

slipstream

Wearb wrote: »

Judging by your spirit level, any little rise at the end would most likely sort you out. Even if that meant taking a saw to a bend to make it suit.
Maybe gouge out that silicone and stick a little wedge under it to rise it a little.

the attached show the bend and the spirit level more clearly (and that i raised the far end to match the collar).

could the bend be cut back by a couple of cm?

Dtp1979

Commissioning should be done by the installer. Simply ask the installer for the cert 2. If he can't supply you with one then your boiler was illegally installed. A cert 2 says the boiler is installed properly and is burning safety. It says a lot more than that but that's the basic jist of it

slipstream

Dtp1979 wrote: »

Commissioning should be done by the installer. Simply ask the installer for the cert 2. If he can't supply you with one then your boiler was illegally installed. A cert 2 says the boiler is installed properly and is burning safety. It says a lot more than that but that's the basic jist of it

this is our first gas boiler so i guess we must a cert of some kind but we have not got a copy yet.

Wearb

slipstream wrote: »

the attached show the bend and the spirit level more clearly (and that i raised the far end to match the collar).

could the bend be cut back by a couple of cm?

I don't think that bend can be lowered without compromising its seal.

As said, get the installer to sort it. That is what he gets paid for.

slipstream

Wearb wrote: »

I don't think that bend can be lowered without compromising its seal.

As said, get the installer to sort it. That is what he gets paid for.

i certainly will ask them to sort it! i just wanted to know what the possibilities were and thanks for helping with that.

DGOBS

Remember too that if a flue on a condensing appliance is not angled correctly there is a possibility of the condense trap not priming and drying out, in which case flue gas could possibly enter a premises through the condensate drain, so make sure the correct fall back to the appliance is checked and corrected.

Also, from your pictures ensure the correct clearance is there to the opposing wall (unless you fit the plume displacement kit as above)

And, don't see your condensate discharge (where is it running to)? or don't see your safety valve discharge piped to outside either.

You are entitled to a gas cert upon completion of gas works, as above.

slipstream

DGOBS wrote: »

Remember too that if a flue on a condensing appliance is not angled correctly there is a possibility of the condense trap not priming and drying out, in which case flue gas could possibly enter a premises through the condensate drain, so make sure the correct fall back to the appliance is checked and corrected.

Also, from your pictures ensure the correct clearance is there to the opposing wall (unless you fit the plume displacement kit as above)

And, don't see your condensate discharge (where is it running to)? or don't see your safety valve discharge piped to outside either.

You are entitled to a gas cert upon completion of gas works, as above.

thanks for your advice and i will ask about the clearance to the opposing wall.

note that the condensate drain goes into the drains through the floor slab.

is there any chance that the internal condensate pipe within the flue would be angled properly but the external flue would be level?

Dtp1979

slipstream wrote: »

thanks for your advice and i will ask about the clearance to the opposing wall.

note that the condensate drain goes into the drains through the floor slab.

is there any chance that the internal condensate pipe within the flue would be angled properly but the external flue would be level?

It's possible. Ring precision heat in Dublin. They'll tell you

DGOBS

If it was angled properly, you shouldn't have that amount of condensate on your footpath

rightjob!

what was the outcome of this?

slipstream

rightjob! wrote: »

what was the outcome of this?

Precision Heating recommended a plume kit but the plumber added a slope instead (to save money I would guess).

There is still a puddle but it is now smaller (as per attached). At least the site of the house is not being splashed now so we are a bit happier.

Slip

Dtp1979

slipstream wrote: »

Precision Heating recommended a plume kit but the plumber added a slope instead (to save money I would guess).

There is still a puddle but it is now smaller (as per attached). At least the site of the house is not being splashed now so we are a bit happier.

Slip

And did you receive a CERT 2 from the installer?