Chimney fire causes?

[Stubby]

Years ago we had a chimney fire . It was back when we had an open fire . Swept the flue once a year and always burnt well seasoned wood . Could not understand it . Was not till a few weeks later that the kids admitted to chucking the plastic wrappers from a toy on the fire . It caught alight and floated up and stuck on the top bend .  The fire brigade showed were it was with an infra red camera in the loft . Extinguished it with a hose with a sort of " watering can rose " on the end . Pin point accuracy and no mess .

[MattyF]

Folks have had there esse for 8 years and never had a chimney fire , they only burn soft wood with the occasional large very dead bit of oak to keep it in all night. It does behave very differently with hard Wöod though can get so hot it goes off the temp gauge from when I’ve used it.

[SbTVF]

This may be a daft question but... how does one become aware of there being a chimney fire if you’re sat in the house? Especially minor ones,
aside from the wall potentially setting on fire I suppose?

[Stubby]

11 minutes ago, SbTVF said:

This may be a daft question but... how does one become aware of there being a chimney fire if you’re sat in the house? Especially minor ones,
aside from the wall potentially setting on fire I suppose?

A roaring sound like a jet fighter taking off ...........

[SbTVF]

A roaring sound like a jet fighter taking off ...........

Coming from the chimney stack rather than the stove I assume?

My stove will make that kind of sound on lighting but thats down to the air draw through it while the primary air level is fully open.

[Stubby]

1 hour ago, SbTVF said:

 

 

Coming from the chimney stack rather than the stove I assume?

My stove will make that kind of sound on lighting but thats down to the air draw through it while the primary air level is fully open.

 

Its louder than normal . You would know .

[richardwale]

Sounds like Concorde is in your liner!

[Alycidon]

Has David Randleson or Greg at Esse been spoken to ?,  if not I suggest you do so,  they are on Extension 4.

 

Smoke coming back into the room is always poor flue performance,  from memory you need at least 12pa from from the flue to pull the gases around the ovens,   this is somewhat higher that is usually required for stoves.   Why this is could be a short flue,  changes in direction of the flue,  downdrafts, poor quality fuel or running the stove closed down for long periods thus not maintaining heat in the flue.  An overly long flue of say 11 or 12m could also cause cold plugging at the top.  

 

Was the stove installed and signed off by a Hetas engineer,  ( there are other self certificating schemes which are acceptable) ,  if so I assume you have called them in to check it.  Has anyone checked the flue draft reading?,  thats usually the first port of call assuming the fuel issue has been cleared.  If the reading is below 12PA then it needs improving,  typically with a wind driven rotary cowl. 

 

Which Esse model is it ?, ( I am an Esse dealer),  if with a boiler running CH then has a Boiler Control unit been fitted,   this allows the fire/cooker to get to to temperature before it allows cold water into the water jacket.   You dont usually fit a BCU on a DHW boiler as they are an indirect system.   So the water running through the boiler heats water in a tank by warming the pipes,   so water running through the boiler does not appear in your bath.  As there is far less water to heat this allows the cooker to get up to operating temp fairly fast,

 

16% is the maximum logs mc advised to use,   most KD I have seen is around 20%,  thats why I bang on about it.  Are the logs of a suitable diameter,  125mm/ 150mm average should be Ok.

 

One final thought,  I have seen a flue liner blocked solid in only six weeks of burning wet wood,  liner had to be replaced.  If you have been burning wet wood this may be the issue.

 

A

Edited February 13, 2018 by Alycidon

[bankhouse builder]

I definitely think a flue problem the twin walls are prone to it don't fit them any more due to the hassle I have had with them over the years. The last one which I was involved with we swapped it for a  proper masonary flue with clay liners in end of problem. The twin walls are insulated but only about 30mm of rockwool. I would try and insulate the flue as much as possible inside the property so the gases are kept as hot as possible when they leave the roof space.

I had one call back we had built a garden room which they had a wood burner installed by another company they said my roof was leaking as they had water running down the side of the flue and dripping off when it got to the bend. I stripped the slates off around the flue everything perfect you could see the beads of condensation on the outside of the flue in the roof space area which was only 400mm high . I packed rockwool round it problem solved.

 

[openspaceman]

30 minutes ago, Big J said:

16% might well be what performs best but it's just impossible for anyone in the UK to achieve drying or storing firewood outside. Equilibrium moisture content up in Central Scotland is well over 20% during winter (about 24% here at home, as we are in a cold spot and relative humidity stays high). How would you suggest we that people in the north of the UK or on the west coast achieve 16%? Genuine question, not being difficult 

Big J

 

What is the current temperature and relative humidity where you are?

 

It's joiners and craftsmen that are most interested in equilibrium moisture content as  they can then make a judgement about how the finished article will "move" as the seasons change with central heating being also a factor.

 

As such the moisture content is often quoted as a % of the oven dry weight, rather than the % of the wet weight we tend to use.

 

So whilst the wet weight basis and dry weight basis converge at 0% a moisture content of a bit less than 17% wwb is equal to a moisture content of 20% dwb.

 

The equilibrium moisture content hardly changes with normal ambient temperature in UK, about 2% dwb between 0C and 30C so the main variable is relative humidity.

 

Here is Surrey it is 6C and RH is about 90%, because it is raining, so the equilibrium moisture content of wood should be about 22% dwb  18% wwb but as it takes time for the log to gain moisture on average in the winter it will be a bit lower, as long as it cannot be re wetted.

 

In high summer with a temperature around 20C and RH 40% it will drop to 8% dwb 7.4%wwb.

 

In winter when we need to burn logs I would expect it to hover just below 18% mc wwb.

 

In practise I have done rather badly with drying this year's logs, I'm not sure why but possibly too much oak which did not dry well