Temperature Top of Flue

[NorthwichTrader]

Does anyone have any temp figures for the flue where it enters the collar?

The reason I ask is do you think 180 deg heat-resistant paint would be good enough for painting the ring-trim that fixes to the ceiling?

Many thanks,

Stuart

[nicknorman]

It's a bit of an open ended figure. Normally the flue will be only warm at the top. However an "operator error" such as leaving the stove bottom open by accident, could see quite high temperatures. However I'm inclined to think that if the top of the flue exceeded 180, the paint blistering would probably be the least of your worries.

[davidg]

I ran some tests on a Squirrel last year. Highest temperature measured on the flue was 132deg near the bottom; top of flue got to 94deg. Tiles by back corners got to 115deg but they were on insulating board plus air gap.

[John V]

Several years ago, after a too much resinous wood being used in my stove I had a chimney fire, The results were spectacular and chastening. The centre section of the flue was a bright cherry red which I understand is about 1,000 degrees c. The top of the flue where it passed through the deckhead was dark red so something above 500 degree c.

After the event I improved the heatproofing around the flue, which had survived.....but only just !!! the cement board was degraded but still intact.

The single walled enamelled flue survived (although it is now more grey than black)

 

 

eta have you looked at the high temperature paints used for motorcycle exhausts ? they come in a range of colours

Edited December 11, 2015 by John V

[dor]

I really struggle to get the flue (6mm steel tube) up to 200C about 30cm above the stove. Normally it is much less than that, which of course doesn't help with tar build-up.

[Graham.m]

Does anyone have any temp figures for the flue where it enters the collar?

The reason I ask is do you think 180 deg heat-resistant paint would be good enough for painting the ring-trim that fixes to the ceiling?

Many thanks,

Stuart

 

My Morso Squirel here runs with a thermometer on the chimney. Normal flue temperature about a foot, 300mm, above the outlet is order of 150C to 200C on a gentle burn, shut down to keep it in temp tends to be about 75C. It is not difficult to achieve temps of 300C and this is within the stove's normal burning range.

 

The heat dissipation from the flue is quite fast and I suspect that you will get away with with 180C paint.

[Graham.m]

I really struggle to get the flue (6mm steel tube) up to 200C about 30cm above the stove. Normally it is much less than that, which of course doesn't help with tar build-up.

 

 

That sounds to me as if the wood s not fully seasoned.

 

I burn a mixture of anthracite and wood. That way the anthracite give me a gentle fire, bottom vent open about one turn, and the wood give the extra quick heat, top open about two turns. I believe the amount of ventilation the stove will use is to an extent related to how good the the chimney's natural draft is.

Edited December 11, 2015 by Graham.m

[dmr]

Stove just ticking over (on coal) right now, thick walled single skin flue,

48 at top, 94 at bottom. Have never seen more than 190 at the bottom, but have not yet measured when going flat out on wood.

 

................Dave

[dor]

 

 

That sounds to me as if the wood s not fully seasoned.

 

I burn a mixture of anthracite and wood. That way the anthracite give me a gentle fire, bottom vent open about one turn, and the wood give the extra quick heat, top open about two turns. I believe the amount of ventilation the stove will use is to an extent related to how good the the chimney's natural draft is.

2 - 3 year old hard wood, i.e. well seasoned.

 

I think it is just the design of the stove (Brunel 1A) - it does have a fairly tight baffle plate at the top which limits the amount of draw. I have had it up to 250 - 260C but it takes a while to get there. Having a relatively thick steel flue probably also limits the external flue temperature indicated.

[Graham.m]

2 - 3 year old hard wood, i.e. well seasoned.

 

I think it is just the design of the stove (Brunel 1A) - it does have a fairly tight baffle plate at the top which limits the amount of draw. I have had it up to 250 - 260C but it takes a while to get there. Having a relatively thick steel flue probably also limits the external flue temperature indicated.

 

Is it dry wood as well. I know on odd occasions here I have brought logs in that had been in the rain and they were tarry. All though logs from the same batch dry were OK.

 

Yes your thick flue will take a while to heat through.

 

Well just found mine down at about 25/30, given it a quick riddle opened bottom door chucked a coupe of logs on and temp is climbing. Up at 150C in the few minutes it took to write this. bottom shut.

Edited December 11, 2015 by Graham.m

[system 4-50]

What are you guys using to measure the temp? Ok, a thermometer. But which? I have bought several in the distant past that have been rubbish.

[Jess--]

at home with my big boiler (which runs on chipboard offcuts) we get quite a bit of tar, which if left unchecked rolls over within the flue and partially blocks it (the boiler is in an external building so CO is not a concern)

 

under normal operating conditions (keeping 26 large radiators up at 75 deg C, plus a huge tank of hot water, and some crude underfloor heating in the workshop) the flue is not normally hot enough to melt tar.

 

when we burn the flue out (deliberately) the whole flue glows cherry red and the top looks like a jet engine running (perfect cone of blue flame out the top)

 

I should add that our flue was made to take this punishment as we knew the fuel we would be using and that we would be burning it out when needed (flue is 10" diameter tube with 10mm walls

[John V]

Ha! if mine was anything to go by, it didn't just look like a jet engine......it sounded like one as well !!!

[dmr]

What are you guys using to measure the temp? Ok, a thermometer. But which? I have bought several in the distant past that have been rubbish.

 

The cheap hand held infra red things (with laser pointer) that you get on eBay are dead good. Every boat should have one.

Can be inaccurate on shiny/reflective surfaces but otherwise impressive.

 

.................Dave

[NorthwichTrader]

My goodness, this forum is such a formidable resource, I'm just SO glad I found it!

Thank-you everyone, I'm very grateful.

Compliments of the season to you all,

Stuart

[Richard10002]

At the bottom of my flue it can get up to 250C, and about a foot below the ceiling and collar, it gets up to about 180C/200C. I'd guess it will be less at the collar. It could get higher, but I close things down if it gets up to 250C just above the flue.

[nicknorman]

At the bottom of my flue it can get up to 250C, and about a foot below the ceiling and collar, it gets up to about 180C/200C. I'd guess it will be less at the collar. It could get higher, but I close things down if it gets up to 250C just above the flue.

Blimey you folk run your stoves hard! Our flue is rarely too hot to touch at mid-height. Are you sure you're talking abou C not F?

[Phil Ambrose]

Ha! if mine was anything to go by, it didn't just look like a jet engine......it sounded like one as well !!!

I know that one only too well. We lived in am old 16th century cottage and it had massive internal chimney, one day we had a chimney fire and the noise was horrendous with a huge spout of flames reaching into the night sky, very rural location with retained fire fighters so when I rang they advised me to cover the fire in the hearth with ash (which I'd already done) and sprinkle water on it, the steam kills the fire in the flue. By the time the lads arrived it was out so all they had to do was check it all out. But I've never forgotten the noise!!

Phil

Edited December 12, 2015 by Phil Ambrose

[Richard10002]

Blimey you folk run your stoves hard! Our flue is rarely too hot to touch at mid-height. Are you sure you're talking abou C not F?

 

On Mine, the 250C just above the stove is usually a bit after I've lit it, and the air vent is wide open. If I left it like this, the boat would get way too hot!

 

I have a Stovax stovepipe thermometer at both levels and they have a grey area between about 135C and 250C where they suggested the fire is burning at the right temperature.

[Chewbacka]

 

On Mine, the 250C just above the stove is usually a bit after I've lit it, and the air vent is wide open. If I left it like this, the boat would get way too hot!

 

I have a Stovax stovepipe thermometer at both levels and they have a grey area between about 135C and 250C where they suggested the fire is burning at the right temperature.

I have a stovax as well and aim for about 150C on the flue just above the stove.

Still tends to get a too warm in the boat unless it is very cold outside.

[GUMPY]

Hobbit stove in "sleep" mode, which it is 97% of the time burning Phurnicite, boat air temperature 22C, eco-fan spinning nicely. I can put my hand on the pipe at roof level for a second or so but can't at the bottom.

[NorthwichTrader]

Thanks, again, all!

Can I ask a related question, as the original question was related to painting the upper ring, which isn't actually touching the flue, and whether 180/190 degrees was an acceptable tolerance?

I've put the whole thing together this evening and actually quite like the 'burnished' (rough sanded) steel colour of the outer ring, which I originally intended to paint white!

Is there a clear heatproof product I can put onto bare steel that will preserve the colour of the steel itself? I know I can paint it silver, but that doesn't quite do it...the uniformity of colour, the look would be lost!

As always,

Thank-you,

Stuart

Edit to add image

Edited December 12, 2015 by NorthwichTrader

[Graham.m]

Thanks, again, all!

Can I ask a related question, as the original question was related to painting the upper ring, which isn't actually touching the flue, and whether 180/190 degrees was an acceptable tolerance?

I've put the whole thing together this evening and actually quite like the 'burnished' (rough sanded) steel colour of the outer ring, which I originally intended to paint white!

Is there a clear heatproof product I can put onto bare steel that will preserve the colour of the steel itself? I know I can paint it silver, but that doesn't quite do it...the uniformity of colour, the look would be lost!

As always,

Thank-you,

Stuart

Edit to add image

 

I am wondering if a good quality external varnish would do the job. They are designed to take the sun's heat and wood that has had the sun on it can be very warm to the touch.

Edited December 13, 2015 by Graham.m

[Neil Smith]

You can buy clear engine lacquer from most good motor factors or on ebay.

 

Neil.

[NorthwichTrader]

Many thanks, gents! Just bought some engine and exhaust lacquer that can be painted directly onto steel...perfect, thanks, Neil!