Double versus Single wall pipe and effect on draft

[DrivenByDemons]

Like many others here I have been battling an overdraft situation ever since I installed my PE Spectrum in late 2007. I have 22' of 6" Class-A and 6-7' of doublewall stovepipe. If I leave the air control open when I reload I can get the inside pipe of the doublewall glowing dull red within 7-10 minutes at the connection to the stove, flames are shooting right up the pipe. (I can see this because of the hole used for the keydamper in the outside section of the doublewall)

Every year I try something new to calm this thing down and I'm thinking of switching to singlewall pipe to see if that would help. I have installed a pipe damper, changed the door and glass gaskets, and verified ash dump is sealed. All is good from the stove end, the damn stack is sucking like a vacuum. Last season when I cleaned the chimney I removed the stovepipe and just the section of Class-A could suck a kleenex right out of the house when the outside temp was around 50F. I've heard of people happy they could get some cigarette smoke to go up their stacks, mine could almost take the butt right out of your hand.

Would switching to single wall help much??? I can easily get outside doublewall pipe temps of 600F 18" up from the stove with the air control shut all the way down. Those readings are using an IR thermo. I really feel like a barometric damper would be the best cure but I get why those are frowned upon so I'm thinking of trying the pipe next.

 

[pen]

Damn that's hot.

I doubt single wall will do a thing here.

You get much creosote in this pipe?

I think this might be a case where if this were my home, I would try a baro damper.

100% sure none of those stove gaskets leak? Man that is hot. No hidden cracks somewhere?

pen

 

[DrivenByDemons]

Never had an ounce of that black creosote, even at the top. Just get a very small amount of that brown powdery stuff, maybe 3 cups for 1 to 1 1/2 cords each year. I have gone over the gaskets at least 100 times and the stove is tight. I've done the incense test everywhere and have no problems. My flue temps are always so much higher than most of the others posts I read about too. Most seem to have lower stack temps and higher stovetop temps. I usually have equal or even higher stack temps. It only makes sense that all that heat is getting sucked up the pipe too quickly. I should take a video of the kleenex getting sucked up the pipe. It's actually kind funny to see but seems excessive, don't you think???

 

[pen]

yea, my chimney wouldn't suck the sneeze up, let alone the kleenex and I have no problems w/ a lack of draft.

If you are offering a vid, I certainly won't be one to stop you! Love them.

I take it this problem is constant and not just occasionally?

pen

 

[DrivenByDemons]

Ha! I'll do a vid for ya but not tonight. Wife and kids are passed out already from the time change and I don't want to wake em up.

Another thing I forget to mention. The pipe temp drops off really quickly as I go higher up the pipe. Maybe 200-250 5' up. Just seems like more proof there are flames getting sucked up the pipe. Anyone else around here use a barometric damper on a wood stove????

 

[laynes69]

If your considering trying a barometric damper, I would purchase a inclined manometer to verify draft. If the draft tests out high, it's the chimney, if low draft there could be leaks in the stove. Those temps sound extreme. Dwyer makes a good manometer for around 40-50.00. There's also eBay for used draft measuring tools.

 

[DrivenByDemons]

yea, constant problem. Like I said, 50F outside and still pulls the tissue up. When it's super cold out and windy I won't fill the stove cause it causes me too much anxiety. Plus I can't trust the wife to load things up when I'm not home cause she tends to leave the air open for too long. I've explained to her what's going on but you know how that goes...

 

[DrivenByDemons]

If your considering trying a barometric damper, I would purchase a inclined manometer to verify draft. If the draft tests out high, it's the chimney, if low draft there could be leaks in the stove. Those temps sound extreme. Dwyer makes a good manometer for around 40-50.00. There's also eBay for used draft measuring tools.

You know what, I'm gonna do this. Is there a model you recommend??? I actually tried this once with an old analog meter I borrowed from work but it wasn't sensitive enough, I think it read from 0-5.0 inches or something like that. I'll spend 50 bucks to get a real answer on this.

 

[laynes69]

We use a barometric damper on our wood furnace. It's EPA certified, non-cat. There's a big difference with and without. Our chimney is 32' tall with a insulated rigid liner. I have tried a key damper, and reducing the air intakes down to reduce draft. In the end the baro was our best option. The draft remains the same through the whole burn, which increases efficiency. I've seen a few manuals for woodstoves where a baro was recommended for an overdraft.

 

[DrivenByDemons]

We use a barometric damper on our wood furnace. It's EPA certified, non-cat. There's a big difference with and without. Our chimney is 32' tall with a insulated rigid liner. I have tried a key damper, and reducing the air intakes down to reduce draft. In the end the baro was our best option. The draft remains the same through the whole burn, which increases efficiency. I've seen a few manuals for woodstoves where a baro was recommended for an overdraft.

Sounds exactly like my setup. I also adjusted the stop on my air control so I could turn it down just a little more and that worked great until the end of the burn where things would kind of fizzle out and not burn completely. Where do you install that baro damper??? have you had creosote problems???

I just found this and am going to pull the trigger right now.

http://www.amazon.com/Dwyer-Mark-Model-Inclined-Manometer/dp/B003NUVVV6

 

[laynes69]

We bought a Dwyer mark II model 25 inclined manometer from drillspot. It's an excellent tool when it comes to troubleshooting. Ours is a couple feet up the flue from the furnace. We get very little creosote. As long as your burning seasoned wood and the stove is burning correctly there should be little creosote formed. Its on a smoke dragon where I would worry. Keeping one set at .06" will allow for a strong draft while keeping the baro from opening too much.

 

[soupy1957]

To discuss a damper is (imho) more appropriate than whether to use a single-wall or double-wall flue pipe. After all, the intent (I believe) of the "double-wall" flue pipe was to decrease the distance from a wall.

With regard to draft, I was taught that it had to do with the elevation of the home, and the height of the chimney (there are Codes for this), relative to the home.

Talking about a damper makes more sense based on your needs.

-Soupy1957

 

[woodmiser]

So why wouldn't a damper work? It basically shuts the chimney down. Did the damper you tried have holes in the damper plate? If so maybe it's not restrictive enough?

 

[fire_man]

I think the double wall not only reduces clearance requirements, but also promotes a better draft because the it keeps the inner pipe warmer. But like Soupy says, it's probably not causing excessive draft all by itself, there are other factors.

 

[DrivenByDemons]

yea, I have a damper in it and can keep it completely close 100% of the time I use it and it really doesn't do much. The thinking behind the double wall pipe is to draw more heat from the flue gasses and slow down the draft. I'm not going to speculate any more on this problem till I receive my manometer. Should be here by the end of the week.

 

[joecool85]

I want to see a video of the tissue going up the chimney! Maybe step outside and see it fly out the top, that'd be cool!

Also, I'm interested in hearing what you get for results on the manometer.

 

[blel]

From what I remember when I installed my Eng 13, the clearances if using double wall were greater.
The theory was that it created more draft, thus higher pipe temps.

 

[begreen]

yea, I have a damper in it and can keep it completely close 100% of the time I use it and it really doesn't do much. The thinking behind the double wall pipe is to draw more heat from the flue gasses and slow down the draft. I'm not going to speculate any more on this problem till I receive my manometer. Should be here by the end of the week.

I'm wondering if you can remove a section of class A pipe. How much pipe is outside, above where it penetrates the roof?

 

[DrivenByDemons]

I can't... Need to be 2' above highest point within 10' and my roof pitch makes that pretty high. Good suggestion though...

 

[BKInsert]

I can't... Need to be 2' above highest point within 10' and my roof pitch makes that pretty high. Good suggestion though...

Yes but your draft is "supper" strong, so you can probably get away with it, I think it is a good suggestion! My flue line is only ~13 feet, definitely not ideal, lower than highest pick, but it works fine! It depends on so many variables.

 

[DrivenByDemons]

I thought that was code??? Doesn't matter anyway as I built a chase around it so I don't have to see all that pipe. I suppose I could cut the chase pretty easily too but I swear that it was code to stay above that peak.

 

[BlankBlankBlank]

We bought a Dwyer mark II model 25 inclined manometer from drillspot. It's an excellent tool when it comes to troubleshooting. Ours is a couple feet up the flue from the furnace. We get very little creosote. As long as your burning seasoned wood and the stove is burning correctly there should be little creosote formed. Its on a smoke dragon where I would worry. Keeping one set at .06" will allow for a strong draft while keeping the baro from opening too much.

So how does one use a manometer?

 

[laynes69]

Once you fill your manometer with fluid, you level and set it to .00". You drill a 1/4 or 5/16" hole in the flue pipe behind the collar of the stove and insert the manometer. One trick is to get a piece of copper tubing to place the rubber hose onto so it doesn't melt. When the readings are verified then your baro can be set to your specific draft requirements. If a higher draft is needed a washer or two on the weight will keep draft a little higher.

 

[DAKSY]

I can't... Need to be 2' above highest point within 10' and my roof pitch makes that pretty high. Good suggestion though...

What IS your roof pitch? Multiply the top number by 10 & add 24".
That will be the actual dimension to meet code...
e.g. 7/12 pitch: 7x10 = 70...+ 24 =94" out of the roof at the upper side
I'm also thinkin that you've got too much pipe...
Most TOTAL runs of 24' are too tall & require a GOOD Damper...
Are you sure it's functioning correctly?

 

[DrivenByDemons]

yea, I know it's an old thread but I have an update

Towards the end of the season last year I decided to get some concrete readings on things. Picked up a Dwyer manometer and tel-tru thermometer. Here are two scenarios I had last February. Of course, like everything else I was going to ask about this over the summer but put it off and now it's getting cold out and here I am.

First readings:
12mph wind
27 degrees F outside
Had nice stable secondary burn about 1/2 hour after I reloaded with a full load of 1 year seasoned oak
Air control set as low as it will go
readings 18" above stove through DW pipe - stack temp 950F - .18 inches on manometer (triple recommended max???)

Second Reading:
No wind - calm
18 degrees F outside
only coals, no active flame
readings 18" above stove through DW pipe - stack temp 575F - .12 inches on manometer.


I'm sure some people thought I was joking about sucking the Kleenex thought the pipe but as you can see I have a massive draft. I never took an idle reading with no fire but I could probably do that tomorrow. temps are in the 50's here now. I have had a key damper in this thing and it's worthless. Makes zero difference no matter what I do. So now I have 2 questions.

If I could drop the height of my chimney 3' would that help at all? That would only be about a 10% reduction overall and it would be a PITA to do but if it will make a difference I'll do it. Is my only other option a barometric damper?