Wood heater flue replacement

[Cliff Rogers]

We have just bought a new wood heater & the flue needs to be upgraded/replaced.

Following are the pics I took along the way.

Does anybody have a copy of AS/NZS 2918:2001 ?

I used the one page instructions that came with the new flue kit & bits I managed to find on the internet.

Pages 4 to 7 of this doco was handy even thought it was for a different wood heater. Fig. 6 & 7 suit my installation best.

First 4 pics are of the old flue coming apart.
Pic 5 shows the framing after I lifted the sheet.

[Cliff Rogers]

pic 6 spreading the framing to suit the larger flue

pic 7 using some of the old sheet screws to hold the framing in place

pic 8 metal brackets cut & bent to shape

pic 9 outer flue hung in place supported by a sheet of material tacked across the beams inside the house. Positions marked & metal bracket tacked in place. At this step, a torpedo level was used to get the flue verticle & holes were drilled through the metal brackets into the flue ready for rivets

pic 10 outer flue removed & metal brackets nailed in place.

[Cliff Rogers]

pic 11 non-combustable packing nailed in place

pic 12 new flashing put in place. (not supplied in the kit, I had it made to suit) Thanks to the tip from Journeyman Mick for this idea.

pic 13 hole maked & cut out undersize

pic 14 edges kerfed(?) ready for bending

pic 15 closer pic of 14

[Cliff Rogers]

pic 16 bending up the flashing with the correct metal bending tool. (tile cutters )

pic 17 ready for the outter flue

pic 18 outer flue hung in place

pic 19 close up from the top

pic 20 lined up verticle for fixing. (rivets through holes made earlier)

[Cliff Rogers]

pic 21 flashing folded in to the outer flue & coated with neutral cure silicon

pic 22 dektite put in place & streached down & marked & the pulled up to have silicon bead run aroun the mark so it will seal

pic 23 dektite put in place & popriveted down with more silicon under the edge

pic 24 stay brackets put in place making sure it is verticle

pic 25 strap fixed to the outter flue

[Cliff Rogers]

pic 26 the finished flue kit with the cowl in place

[silentC]

I like the metal flashing idea. Is that a standard practice in canetoad land, or was that your invention?

I installed a fire the weekend before last. Just used a dektite straight onto the roof sheet. It hasn't leaked as yet.

One thing I noticed the first time I lit it. The cowl was sitting right down over the outer when we put it on but after the flue warmed up, it lifted by about 20mm and exposed the vent holes. Does yours do that?

[Cliff Rogers]

Journeyman Mick may wish to add some comments but he said the trick was to pretend that silicon hadn't been invented & have the flashing made with that in mind.

The flashing I have neatly spans the corrigations in the custom orb & has a sligh crease down the middle to make the water run off to the sides instead of straight down the flashing.

Turning the flashing up as in pic 16 is so that any water that does make its way under the silicon will not drip down inside the ceiling.

Any questions, comments, corrections in spelling & nomenclature welcomed. IE: dektite, thanks SC

[Cliff Rogers]

...One thing I noticed the first time I lit it. The cowl was sitting right down over the outer when we put it on but after the flue warmed up, it lifted by about 20mm and exposed the vent holes. Does yours do that?

We haven't used ours yet.

I'd guess that the active flue expanded more than the outer flue & lifted the cowl up.

[silentC]

Well yes, that's what's causing it. Just seems like a poor design to me. I reckon the cowls should be made to allow the inner to expand and contract without raising the cowl. The inner ring of the cowl is a tight fit over the end of the flue though, because the fat end is up. We thought about screwing the cowl to the outer but that would probably be a bad idea if the inner doesn't give. 20mm is a lot.

[Cliff Rogers]

Ours is a Maxiheat Drop Box Default Flue Kit.
The instructions say "Trim the two layers of gal to allow the cowl to sit neatly onto the active flue lenght. The gal should be trimmed not at the top but at the bottom, where it joins the lenght underneath. Now secure the cowl onto the active lenght of flue"

The queer bit is that the picture right below it shows screws through the skirt of the cowl into the outer flue & the tube in the centre of the cowl that goes down inside the active flue is marked as "100mm Telescopic Extension"

That suggests to me that the cowl is held to the outer & the active can slide up & down the centre part of the cowl.

I will get up on the roof & have a look at it right after I finish my coffee.

Oops, urgent job just came in, have to do it later.

[silentC]

Don't forget your PPE

[Cliff Rogers]

Sunglasses.

[Barry_White]

Just used a dektite straight onto the roof sheet. It hasn't leaked as yet.

Hi Darren

I have had two flues with the Dektites just siliconed down to the corrugated roof for 23 years and they have never leaked.

The flue for the slow combustion stove doesn't have a cowl on it and the flues are just galvanised pipe and it is just starting to corrode around the top. I wish I had used stainless steel now but back then there wasn't much stainless around for flues. It looks like I might have to replace it next year.

[silentC]

The stainless doesn't last forever either, but it's better than gal! It ain't cheap though. I had to get my BIL to make up a replacement length for me and it was $46 in the book. Lucky for me he married my sister

The dektites seem to work pretty well. They should at least last for the life of the flue. We got this flue with the fire - both second hand. One of the s/s inner lengths had burnt through a seam but the dektite that was still attached to the outer was in good nick. We thought about reusing it but it was a bit small and we had a nice new one, so it's gone to the tip before it's time.

Hope Cliff hasn't fallen off the roof. I'd feel a bit guilty about it...