Blocked Woodburner Flue

firefox1956

Had a woodburner put in just over 3 years ago.
Standard installation with a standard cowl similar to this but stainless steel.
http://www.toolstation.com/shop/p71603?table=no
Had the flue swept every year & just a reasonable amount of soot etc removed each time.
Not burnt anything any different over the 3 years so no changes of use.
No real problems up to about 3 weeks ago.
Stove not drawing very well, smoke coming into the room when lighting but smoke still coming out of cowl etc.
Looked up the flue with a torch, looked pretty well sooted up.
Called sweep out & he swept a huge amount of stuff out of the flue.
What the hell have you been burning etc etc.....
Stove seems to draw better & sweep goes.
Couple of days later I get a right faceful of smoke when lighting stove !!
Got a pair of binoculars & looked up at the birdguard cowl.
:eek::eek::eek:
Absolutely amazed to see the mesh of the cowl so blocked it looked like a piece of carpet had been wrapped around it !!
Got a guy onto the chimney to take off cowl clean & replace after
removing the mesh.........
It won't damn well block again & the birds can take their chances
The question I am eventually getting to is this.....
Should the sweeps brushes have reached & cleaned the birdguard mesh ??
Those I have spoken too seem to think not.
I would appreciate the comments of you chimney sweeps on here.
TIA

footyguy

I don't know specifically about wood burning stove flues, but certainly with traditional chimneys, the only way the sweep could know they reached the end of the chimney was when the brush was seen coming out of the top.

Furthermore, a brush will usually only go one way in the chimney. If you think about it, the brush is generally bigger than the chimney and it's bristles bend as it is shoved up the chimney. If you were to try and retract it, the bristles effectively will anchor into the lining of the chimney, and oinly with great force (and possible resultant damage to the chimney lining) can you reverse the direction of travel.

Of course, once the brush pops out of the top of the chimney, the bristles spread out again, and then go in the reverse direction as the brush is withdrawn.

I don't think professional chimney sweeps use brushes nowadays. I thought they preferred vaccuums. Brushing a chimney with rods & brush is hard physical work.

Greenfires

Lot of people seem to think that! The reality is that you can't sweep a chimney with a vacuum - chimney sweeps all use brushes.

Sounds fairly typical of using housecoal in a stove - though you didn't mention the fuel used. I had a couple of customers who managed to fill the mesh in their birdguards. A sweep will normally get it out - though if the chimney is not lined he may have gone up with a brush that was too big to do the business inside the much smaller cowl. A power sweeping head would have probably gone straight into it and cleaned it all up. In any case if the pot is visible from the ground then it really should have been visually inspected before leaving the job.

How long after the visit did it block? If it was pulling well when he left then it must have been pretty clear at that stage. Burning coal in a stove can make a lot of mess very quickly. That's just one of the reasons why it's not a suitable fuel for a closed appliance (or for the majority of closed appliances at least)

firefox1956

They do use brushes only smaller ones !!
The vacuum is just for cleaning up.

firefox1956

Thanks Greenfires.
Had one 'power' sweep & two 'normal' sweeps so niether of them got to the mesh birdguard.
No one visually inspected the birdguard either even me.
I think it has been a culmination of 3 years burning to be honest.
The very last time it was swept I thought it was not pulling right but thought that is was me being a bit picky!!

Only ever burn wood, pallet wood etc all very dry & clean.
Never ever burn housecoal but use a bit of Oxbow Red which is described as a 'non-smokeless economy ovoid'.
Do you think this might be the cause ??
Just as a note I burn the stove nice & hot all the time, never down in the 'cresote' range of the stove thermometer.

Ectophile

Softwoods can be a bit resinous. So too much pallet wood could lead to tarry deposits in the chimney.

Gloomendoom

If you have removed the mesh guard, be prepared to find your flue full of sticks by the end of spring.

I speak from experience.

Greenfires

The ovoids may well have something to do with it. They're similar to charcoal briquettes in that the customer usually has no idea at all what's in them. The list of "added ingredients" in bbq charcoal briquettes can be as long as your arm, and most of it is nothing you'd cook your dog's dinner over, never mind your own! Anyway - if they're non smokeless it may well suggest there's a fair amount of bituminous coal waste in them, which would certainly not do your chimney any favours. The other issue is that wood and smokeless (or even this stuff) require completely opposite setups to get the best from them. Wood likes a bed of ash and the air supply from above, and smokeless is much better on a clean grate with the air from below. So if you're burning them both at the same time you're always going to be compromising one of them.

Bit odd that none of the sweeps got into the mesh - and rather second rate that it wasn't even checked. Some chimneys can be real pigs to get out the top because of the way they run - you can end up with the brush always coming up under a ledge into a corner and no amount of twisting and turning can get you into the pot. But if it's visible from the ground they should at least have had a squint at it.