Chimney Question

When I built my chimney in my outdoor boiler's building, I researched what size most boilers and stoves were using for chimney flue size. I also asked several installers for advice. I compared firebox size and loading door sizes too.

I had always thought that an 8" chimney was the best. But I went with the smaller of my two choices, which is 6.5" x 6.5" inside dimension square flue red ceramic flue liner. The chimney is inside the heated boiler room, total flue height from boiler to top of chimney is about 12'.

The main reason I went with the smaller choice was that I was told by several installers and chimney sweeping guys that the smaller flue will stay cleaner longer because it will be warmer and accumulate less creosote than a large flue..

With my smaller boiler this chimney worked well, even when I opened the loading door to toss wood or coal on the fire. But with my new, much larger boiler I'm getting a lot of smoke out of the firebox when I open the door to load in more wood and coal. Both the old boiler and the new one have a hinged flap over the top 1/3 of the door opening to help block smoke exiting the doorway, it swings out of the way when loading fuel. However, the new boiler has a much larger door opening, and this is the main problem I'm sure. But I need the larger door opening for faster and easier loading.

I have a smoke diverter built into the firebox, so before I open the door, I slide the diverter open which gives a direct pathway from the firebox to the chimney.. I let it draw for a minute or two to get some velocity up the chimney. I can see a significant increase in velocity of the smoke exiting the chimney when I check outside. I also turn off the combustion blower if it is running.

So my question is this: Many if not most of the folks on this site have a 6" stainless steel flue liner in their chimney. If I install a SS liner I will be reducing the area of the chimney flue from 6.5x6.5" square to 6" round. But the liner will get hotter faster than the ceramic liner. With less area, but round and warmer faster will I get better draft??

So has anyone made a before and after comparison when installing a SS flue liner ?? Does the SS liner pull a stronger draft than the ceramic flue?? The ceramic flue is brand new, clean, and I made sure the joints lined up very well so it is quite smooth all the way.

This is really just a comfort or cosmetic issue for me since the boiler is in it's own building and the only issue is me having to deal with the smoke [burning eyes, and smelly clothes] when loading the firebox. The boiler has plenty of draft when the door is closed, in fact maybe too much draft at times.

Also is has been very warm here for the last week or so, maybe I'm just seeing the poor draft because of the warm outside temperature?? The smoke was still an issue a few weeks a go when it was cooler.

Thanks in advance for any and all replies. Greg L [LsFarm]

Anybody have links to sites where I can price SS liner??

Thanks Greg L

**Broken Link(s) Removed**

Greg

There is a manufacturer in New York...I forgot the name...but I will find it for you...they make a great product...I did a lot of research in SS liners....and there is a difference...and different grades....i got the one that is titanium coated...for coal..less chance of acid corrosion...lifetime guarantee...

The name is on the tip of my tongue..but won't come out...give me time to find out...

This was recommended by 4 stove suppliers...I paid 220 for 15 feet..which was a good price....

I will get back to you....

Al

Thanks John and Al

Do you think a 6" diameter liner will have more draft than a 6.5"x6.5" ceramic flue?? Do you think it would be worth the $3-400 ??

Thanks Greg L

Greg..i could not answer that question if it would be better....I have a 6in flue...it is made of thermocrete...it is basically refractory cement..I had a chimney fire 15 years ago...so busted out all the tiles...and put a ballon type form down chimney and pumped in the thermocrete...let it set up and deflate the ballon....the original flue was 8 inches...

I use the stainless flue for my stove pipes....here is the link to the company..I found it....get the 316TI alloy
**Broken Link(s) Removed**plus it UL tested....for the home insurance people...lol

Al

i have the homesaver ultra pro 6" .06" thick 316Ti alloy 40' the liner,end cap,connector and chimney cap was over 700.00.
Draft depends on many factors how many bends are in the chimney, The height is the chimney located inside or outside the house.
Mine is located inside a masonary chimney that is inside my house so I didn't have to install insulation around the liner..If the chimney is located outside the house then u will need to insulate the liner so that the gases don't cool off to quick..If they cool off to fast then your gonna lose draft.. Hope that helps
I first used my chimney without a liner in it it was 8X8 I had a very hard time keeping a coal fire going unless I kept adding wood to keep the flue temp up. So in my cae installing a ss liner solved my problem

After re reading your post I think your problem is your chimney isn't high enough for a proper draft esp for wood..Most wood stoves require a min of 15 feet and that's if there are no elbows used..I think for every elbow used u have to increase the chimney length by 18 inches don't quote me on that.You have abigger firebox now so you would require more pull (draft)

I bought my liner from
**Broken Link(s) Removed** The sales man installs liners and will help you with anything you need.They also had the best prices at the time I bought my liner. All of the reviews I have read on this liner say it is the best. You won't be able to insulate it with the size of your current liner. I never used my chimney before lining it so I cannot give a comparison on liner vs no liner. The ss liner will have slightly less area than the current flue so it should increase draft. If you give the salesman at the above site a call he should be able to give you a professional opinion as he is a chimney sweep. Hope this helps, Scott

Thanks for the replies, I can add a few more courses and another length of ceramic flue pretty easy. I'm not sure that another 24" of flue height will make a lot of difference. The current chimney is in the inside of the outbuilding and this room is at least partially heated. The portion of the chimney above the roof is probably 6', half of the total chimney height. I don't think it needs insulation and I also don't think there is room for insulation.

I have two elbows both very close to the boiler and a short connector to the chimney, then the chimney is a straight shot up.

I would prefer to get the sections of smooth rigid flue liner, I see no reason to go with the flexible liner. The rigid is more expensive though from what I've seen so far.

I may try lining the flue with regular galvanized as an experiment, I can buy the 22ga galvanized for a fraction of the cost of the stainless and see what difference it makes. I just have to crawl up on the roof or work from the loader bucket to install the liner. This I can do this week. It will be interesting to see if there is a noticable difference.

I just can't leave the galvanized liner in for more than a month or the corrosion may make it difficult to remove the liner. I will have to make sure I use plenty of fasteners to connect the sections, or maybe I'll MIG the sections together so it will be one piece. I don't want to have corrosion and not get all the liner out of the flue after the 'experiment'.

Thanks again. Greg L

Yesterday evening and last night the temperature was around 30* and the chimney was drawing noticably stronger. So I guess at least part of the draft problem was the warm temperature.

This morning I screwed several sections of glavanized 22ga. 6" together and slid it into the ceramic flue. It is too early to tell but it appears to be pulling a stronger draft.

I'll know better when I load up the firebox for the night. That is when there is a lot of fresh fuel, wood and coal, on top of the bed of hot coals.
This is when the most smoke is generated.

I did a little 'networking' and found a friend who's brother is a wholesaler for SS chimney and other chimney products. I will probably go with a SS liner if the glavanized liner proves to be an improvement.

Thanks for the feedback, Greg L