Any log burner fitters out there? Technical query/issue

stalker.308

stalker.308

Well-Known Member
So, long story as short as possible, we had a log burner fitted over a week ago, old open fire out a log burner in. The chimney stack came down to just below ridge height and a twin wall liner put out through the roof, a decision based on a leaning stack.

So burner fitted, flexi going to the loft, a plate on the stack and twin wall going on from that goes through the roof.

The issue- There is a gap down the old void from the loft end, I guess so it does not get damp etc so all that is beneath is the flexi (and obviously at the bottom the register plate) but when the fire is going, as soon as it gets to a certain heat, the attic roof fills with fumes, they smell quite chemical like (certainly not leaking smoke from the burner). If I stand in the loft by the gap to the side of the flexi with a torch, I can pick up wisps of smoke. Its a fully internal chimney, no outside wall, so was not filled with vermiculite.

The fitter has suggested its oil/paints curing, but having had a fire each day for 7 days, nothing too long, any oils or paints would have surely cured by now? Much like the smell that came from the log burner when that was first lit that went after two hours. The other option I guess is our chimney was dirty, which he swept as best he could (indicating room for improvement), but could it be the flexi heating up to such a temperature that is is causing smoke from soot in the chimney that it is leaning against? Smells more chemically than that but. Have not smelt re heated soot before though.....

In a normal case, where the chimney stack is retained, all these smells would just go outside, but as the flexi terminates in the loft, this is not the case. Any thoughts? He is coming back out, but certainly suggesting oils and paints...... but it can only be coming off or being caused by the flexi.....
 
Assuming the flexi runs up through the old flue and then breaks out into the loft to join twin wall before penetrating the roof then it would seem that as the flexi gets hot then then its warming the old residues in the original flue. If the original flue is not vented to the outside world then this problem won't go away.
 
Forgive me for asking, but is the outside part of the new flue above or below the ridge height? I understand your stack comes up short, but does the new flue protrude above this, and clears the height of the ridge?
 
Have you been burning wood on the old open fire ,the resin from this set fire to my father in laws chimney.
And that was a horrible chemical smell ,worth a flexi camera up to have a look??
 
Swedish said:
Assuming the flexi runs up through the old flue and then breaks out into the loft to join twin wall before penetrating the roof then it would seem that as the flexi gets hot then then its warming the old residues in the original flue. If the original flue is not vented to the outside world then this problem won't go away.
Click to expand...
Not what I wanted to hear but what I expected the answer would likely be.

So I guess what can fix it.

Assuming blocking the vent into the loft is a bad idea as the old flue will fill with smoke and it’ll come out somewhere in the house.

Is there a more insulated flexi? It only smells when the fire is super hot.

Insulation in the old flue around the existing flexi?

A filter of sorts on the ‘vent’.

A pipe taking the fumes away much like a bathroom extractor but without the fan...
 
Carry out a pressure test of the appliance and flue system. Heat chimney for 10 min then cap off the terminal and then light a couple of smoke bombs and place in the log burner. Close off all air intakes on the appliance and look for smoke emitting form the flue system with a torch
 
tozzybum said:
Have you been burning wood on the old open fire ,the resin from this set fire to my father in laws chimney.
And that was a horrible chemical smell ,worth a flexi camera up to have a look??
Click to expand...

I do have an endoscope with extender section, will have a look. We burnt some wood but with coal.
 
DEER STALKER said:
Carry out a pressure test of the appliance and flue system. Heat chimney for 10 min then cap off the terminal and then light a couple of smoke bombs and place in the log burner. Close off all air intakes on the appliance and look for smoke emitting form the flue system with a torch
Click to expand...
I have no doubt the burner is not leaking smoke, I could burn all day and have it smouldering and not a smell at all in the loft
 
stalker.308 said:
Not what I wanted to hear but what I expected the answer would likely be.

So I guess what can fix it.

Assuming blocking the vent into the loft is a bad idea as the old flue will fill with smoke and it’ll come out somewhere in the house.

Is there a more insulated flexi? It only smells when the fire is super hot.

Insulation in the old flue around the existing flexi?

A filter of sorts on the ‘vent’.

A pipe taking the fumes away much like a bathroom extractor but without the fan...
Click to expand...
If the old masonry flue is terminated in the loft then I would suggest any vent fitted to it needs to be extended to the outside for the easiest fix.
 
Could you go from lounge level to ridge line in twin skin?
That is how mine is and after the initial paint, chemical smells, has been totally sound since.

Added;
Just as a side note, this was a few years ago and the smells lasted less than x7 days/fires so you obviously have an issue.
 
Under normal circumstances a stainless steel flexi flue is fed down the chimney flue (in my experience) to be fitted to the vitreous enamel pipe emanating from the wood burner that in turn goes through the register plate.
Fitted by this method all the smells, vapours, would be vented out the chimney stack creating no concerns.

The fact it terminates within the loft space and then connected to the twin wall flue you are always going to get that chemical smell because the stainless steel flue when heated to a certain temperature gives off that pungent smell.
The top of the internal chimney stack not being completely sealed also allows the smell and vapours into the loft space.

In the loft space there should be no flexi flue visible only twin wall.
 
The flexi flue does smell a bit when it gets hot for the first few times, as does the twin wall stainless steel. I always just assumed it was surface grease and other crud from the manufacturing process being burnt off.
 
VSS said:
The flexi flue does smell a bit when it gets hot for the first few times, as does the twin wall stainless steel. I always just assumed it was surface grease and other crud from the manufacturing process being burnt off.
Click to expand...
I’m still hopeful Tim, but not abating yet...
 
im no expert but having seen several log burners fitted recently I agree with all said above. Some points to add are:
1) heat rises so obviously any smells from the whole flexi liner length are going to work their way up into the loft.
2) would the flexi liner only burn the residues it touches? so with time this would improve?
3) how long have you run it for because you may need to run it at full tilt for a few days to properly burn all the residues away?
4) a twin wall flue for full length should eliminate the problem as the external wall of the flue doesn't get too hot. 80 degrees at a guess?

a seperate story but we once had a boiler stove that we disconnected the pipes from. It took several fires to finally get rid of the fumes coming from within the boiler and pipes. Hope you solve it
Nick
 
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