wood boiler flue height

[700renegade]

Another question to be settled before I install a used Buderus ( Bosch ) 140k btu wood boiler:

The O&M;manual states for my furnace the minumum flue heights are as follows:
> 7" flue - at least 32.4 feet
> 8" flue - at least 29.4 feet
> 9" flue - at least 26.25 feet

Can this be true? What problems will I have if I use something significantly less?

I'm installing this in an unheated pole shed with about a 9' sidewall height. I've seen where you want to be about 3 feet above any roof within 10' of the pipe - in my case the peak of the roof is probably only 14' high.

Can the heights from the table in the O&M;possibly be correct, or did they mess something up in the translation from German???

 

[Tony H]

The manual for the EKO has some similarly large numbers for the chimney. I and several others have installs with less and when I spoke with the supplier he suggested 12' with 6" pipe and it works ok. I am planning to add a couple of feet because when we get the strong wind from the west it puts some down draft as it comes over the garage and down on the shed. You might try checking with the MFG .

 

[700renegade]

What do you think about the flue diameters? I was originally assuming I'd adapt the 7" from the back of the boiler down to a 6" which seems to be readily available. After downloading the O&M;perhaps I need to go up to 8". Feels like overkill for a modest size boiler, but what do I know.......

Code Inspectors reading the manual????? I'd move to a different locale if I had to kiss the rear of an inspector every time I did a little project.

 

[700renegade]

I'll probably run a stainless double - wall straight up thru the roof steel sheeting so it matches my adjacent Central Boiler corn Boiler. Although if I could get by with it, Id consider trowing a thimble thru the rear wall ( this is an unfinished pole shed ) and go straight up parallel to the wall w/ plain old black stove pipe. I don't know enough to understand the pros / cons of each ( other than the black pipe is about 10% of the money! ). This isn't like an in-home fireplace where a bit of smoke from backdraft at startup is a big problem.

 

[rowerwet]

single wall above the roof could give you creosote problems due to cold pipe. also poor draft for same reason

 

[Hydronics]

I had my Buderus connected to a 16' double wall 7" flue in my out-building and it worked well. I wouldn't use single wall, it will cool too quickly, not draft well and build up creosote. If you have a chimney fire it might not be pretty....