What a difference an insulated flue makes

[Woodworks]

1 hour ago, neiln said:

Another couple of possible differences i thought of. do your parents ever soot the glass?  They will be sooting the flue a little at the same time, maybe you run that tiny bit hotter. Do they shut down and relight every day, but you run continuous?  I'm guessing if they are room heating then they may.  Every start involves a sooty period and a cold flue for it to settle on.

No the glass is always spotless. If anything they run it hotter than ours but it is smaller so less gas to go up the flue. Long stainless flue inside an old stone chimney on an outside wall. Would be better if it had vermiculite beads like Stubby mentions but the chimney is pretty big in places so would take one hell of a lot of beads to do the job. Cant get an insulated liner in as there is a squeeze in the stone chimney and this made getting the single skinned liner in a tricky job. I will just sweep it more often

[richardwale]

15 hours ago, Stubby said:

Mine is an internal flue ( not outside wall ) . Its pretty much as insulated as it could be . 7.5" clay liner surrounded with vermiculite beads with a 6" stainless liner up inside that . 

Exactly the same as ours. We live in 70s built chalet bungalow and each year I get a cornflake bowl of soot coming out and the stove is lit everyday for 6 months

[BowlandStoves]

Was there any internal or eternal damage to your parent's flue pipe?

[neiln]

Could you insulate the liner from the top?  I believe standard rockwool is fine, or purpose made blankets can be wrapped round the liner.  I get the issue with a constriction making it difficult to pull a wrapped liner through but if you can access the top and push, poke, drop bits of rockwool down around the liner and insulate above the restriction that may help a lot.  It's bound to be the top where the gas is coolest and most of the soot is.

 

I sweep my flue with a power sweep/rotary brush system, through the pipes access door, letting the soot fall into the stove. each year I get enough powder to half fill the ash pan. That's from burning 6-7m³ of 18-24 month CSS wood. If I remember next time I'll stop and check on the accumulation of soot after the first 6m, before I do the last 2m,. My stove is on the adjoining wall to next door (so internal flue) but last 2m is above roofline. My guess is that most of the soot is accumulating in that last couple of metres.

[Woodworks]

No damage to the flue last year as it was professionally inspected with a camera when the new stove was fitted.

 

No access around the flue without major masonry work. Might look into a rotary sweep brush as it was one helava job getting the stiff bristled brush up the flue. Yes worst was where the chimney breaks the roof line so more cooling. Oddly there was a block just above the stove but I guess soot had fallen down over the summer and when dad had his first fire this amalgamated into lump. The rest was not too bad. 

[openspaceman]

9 hours ago, neiln said:

Could you insulate the liner from the top?  I believe standard rockwool is fine, or purpose made blankets can be wrapped round the liner.

I haven't got insulated flue liners as my stove vents into a concrete 9" liner and I  depend on the heat from the brickwork to keep the room above warm between firings. I have always intended to sticj=k a thermocouple at the cowl to see how much heat I waste.

9 hours ago, neiln said:

 

I sweep my flue with a power sweep/rotary brush system,

Which make? What colour soot?

[neiln]

Can't remember the brush make but could dig it out and check if you like.  got it online and aid for a top end home owner/semi pro set of rods that are more resistsnt to heat.  my flue has bends, the danger with cheap rods is leave it spinning but not moving and where it touches around a bend it heats up quickly and gets damamaged...so obviously keep it moving but also better rods resist the heat more.  thinki paid about £100 for err  9m of rods and the brush.

here's the set up, vac catches to minimal dust tht might escape (very little as i tape up around a bit of waste pipe and feed th rods in through that).  most soot/creosote falls into the stove.  And the result, 1/3 or 1/2 a ash pan of light poweder, dark brown colour.

 

[Woodworks]

Looking at the rotary sweepers the brushes are lose. Will they remove caked on chunks? The brush on our rods is very stiff and just the right size for the inside of the flue but then its very difficult to push through restrictions. Wish my folks flue just had soot like you have neiln

[neiln]

The brushes are not stiff, it's basically strimmer string.

 

I've read creosote comes in 3 stages, stage one - powdery soot like, easily removed.  Stage 2 - getting wetter and oily/tar like, removable but messier.  Stage 3 - heavy deposits, the oily tar has dried/hardened to thick caked on tarmac like tar.  Removal is hard, wire brushes and spinning chains to break off, but damage to a flue possible.

 

What I take from that is, sweep often enough that you never get type 3, and hopefully not much 2.  Burn dry wood and burn hot and I guess it would take a long long time to get more than type 1.

[openspaceman]

12 hours ago, neiln said:

Can't remember the brush make but could dig it out and check if you like.  got it online and aid for a top end home owner/semi pro set of rods that are more resistsnt to heat.  my flue has bends, the danger with cheap rods is leave it spinning but not moving and where it touches around a bend it heats up quickly and gets damamaged...so obviously keep it moving but also better rods resist the heat more.  thinki paid about £100 for err  9m of rods and the brush.

 

Sounds reasonable, we used Wohler system at work but they cost 4 times that and the expense is not justified for home use. I use ordinary 9" head and drain rods  at home but need something for 5" 904 liner at my daughter's. I think I'll adapt  a nylon brush set to push a standard 5" 2metre flue brush  all the way up and out of the top, ordinary plastic drain rods are too stiff.

12 hours ago, neiln said:

 And the result, 1/3 or 1/2 a ash pan of light poweder, dark brown colour.

 

Chocolate brown and matt seems good, black and shiny flakes bad.