Neo 2.5 free-standing - ? Soot on outside of flue

[DenisT]

Hi, after some problems with my Neo 2.5 (not drawing well) went back to the installer who added a length of flue. This improved the situation markedly. Have noticed though what appears to be soot on the outside of the new portion of flue (photo). Any advice on what would be causing this, and whether it is something I should be concerned about, would be welcome. Thanks. Denis

 

[Ctwoodtick]

I’m not a professional, but I would imagine that some soot buildup like that is normal. You’d probably see more buildup with wet wood or frequent cold starts.
Also, I know that pellet fuel vent can be galvanized on the outside layer of chimney, but wasn’t aware venting for wood could be galvanized on outside as well. I say this bc your pipe looks like galvanized but I could be wrong.

 

[DenisT]

Thanks. There certainly have been a number of cold starts here recently. However, I don’t recall the discolouration on the outside of the flue before the extension was installed. Also, it may be my imagination but it does seem to me that the fire is no longer drawing as well as it was after the extension was first installed. Worried that domething untoward is going on. Will do a physical check of the flue tomorrow.

 

[kborndale]

What is the moisture content of your wood?

 

[begreen]

Looks like the flue temps have been on the cool side at times. This can be due to a single-wall stove pipe cooling, damp wood, and/or smoldering the fire. A flue thermometer can help with keeping the flue gases hot enough for a clean burn.

 

[DenisT]

Thanks. Have now cleaned the outside and swept the inside of the flue. We do tend to run the fire hot but will keep an eye on this. Perhaps a temp gauge would assist in this. The moisture content of the wood is unknown - have ordered a moisture meter so will see what that shows.

 

[TomMcDonald]

My last 3 triple skin flues have done the same and it happens very quickly.
At first I was worried but now I don't care.
Just make sure you don't clean it with an abrasive medium or it'll get worse, and then rust.
The moisture content of my wood is around 14%.

 

[DenisT]

Thanks. Yes the flue is triple-skinned. No abrasives for cleaning as you say. I am waiting for my moisture meter to arrive and will be interested to see what this reveals. Thinking more about begreen’s comments, I have ordered a temperature gauge as well, as there may be something in relatively low temperatures as I still struggle to get what I would call a roaring fire. As noted previously the flue was extended by the installer due to relatively poor draw (difficult to start). This has improved but while I was cleaning the flue I measured from the top of the heater to the top of the flue - 3.8m, when the heater spec is 4m. Perhaps still not enough.

 

[TomMcDonald]

Yep - my Neo had 5 metres and still didn't have crazy draft. My current stove also has a bit under 5 and could benefit from more.

 

[DenisT]

Might be worth an extra half metre. Do you know past what height of flue bracing is required? Installer told me met standard but my flue is 1,9m out of the roof with no bracing - from what I can see there should be bracing if more than about 1.5m. Thanks.

 

[begreen]

The flue should be braced at 5' above the roof exit. Galvanized flue pipe seems to get dirtier faster than stainless and triple-wall insulation is not as efficient as a good double-wall chimney pipe. They may be contributing factors.

 

[DenisT]

Thanks very much. I will get onto this, particularly so as I intend to extend the flue a bit.