Damper in double wall pipe

[Ashful]

I’m planning to install a key damper in a double wall pipe, in the next few days, and wondering how to handle the usual compression spring. Here’s what I have:



So, that spring on the axle near the handle will be compressed so hard it’ll likely deform the outer wall of the double-wall pipe, if I just drill the usual 1/4” hole and insert the rod. What I seem to be seeing, at least in a few cases, is folks counter-boring the outer wall large enough to allow the entire spring and cup washer to penetrate thru to the inner wall. So, the damper fits as if it were in single wall.



This would have the added advantage of making easier to thread the bent axle thru the pipe.

 

[begreen]

The damper is designed for single wall pipe. Is there a reason to not buy the proper fitting as shown in the lower image?

 

[bcrtops]

I haven't done this, but have thought about it, and have seen examples of others doing so.
Buy a 6" & a 7" damper (an 8" might work with mod)
Use the key part of the 7" & the cast iron part of the 6"

You used to be able to buy the 7" size, not sure now. Putting a longer spring on an 8" key would probably work as well. (Or stretch it, or washer it)
Just an idea, that I have seen done.

The ONLY reason I haven't tried this, is my chimney is very short & I'm afraid the damper would restrict the flow enough that I might have draft issues in warmer / shoulder season weather. The damper, even vertical does restrict flow / draft quite a bit -- I've seen figures between 15-20%.

 

[Ashful]

The damper is designed for single wall pipe. Is there a reason to not buy the proper fitting as shown in the lower image?

This is a highly “engineered” piping assembly, made up of about 7 pieces of double wall to make the required precise translation from my stove up and back to my liner at block-off plate. I really don’t want to go thru re-engineering that whole mess, if I can avoid it, and was aiming to put the damper in an existing 30” section of pipe.

Besides, is there anything at all different between the purchased damper section in that lower image, and what I’m planning to do? It looks like that’s exactly what they did, there.

 

[begreen]

Is there a slip section of stove pipe in the system where the damper could be inserted?

Like bcrtops indicated, I think the mandrel would need to be sized to the larger OD of the pipe while the damper sized to the inner ID of the pipe.

 

[semipro]

Just curious @Ashful
Do you have a problem with excessive draft?
I ask only because I was able to address this on our Jotul Oslo installation by restricting the OAK which seems way simpler than installing a damper in the flue.

 

[Ashful]

Is there a slip section of stove pipe in the system where the damper could be inserted?

Like bcrtops indicated, I think the mandrel would need to be sized to the larger OD of the pipe while the damper sized to the inner ID of the pipe.

No slip section. No issue with buying the larger size to steal the mandrel, if they're interchangeable. As I remember, this 6" one was dirt cheap at Tractor Supply Co.

Just curious @Ashful
Do you have a problem with excessive draft?

LOL... are you new here? Yes, my draft is more than 3x BK's "allowable maximum" number. I'm into "voided warranty" territory, on this one chimney. Got a bit of a height issue, you see:



I'm speaking of the 4-story job on the right, but you can also see the shorter chimney on my other Ashford on the left in this photo. Unfortunately, with 20" thick mud-stacked (not slang, the bedding mortar is literally mud from the back yard) stone walls all 'round, there's no chance of an OAK.

 

[semipro]

LOL... are you new here? Yes, my draft is more than 3x BK's "allowable maximum" number. I'm into "voided warranty" territory, on this one chimney. Got a bit of a height issue, you see:

View attachment 221786

I'm speaking of the 4-story job on the right, but you can also see the shorter chimney on my other Ashford on the left in this photo.

Haha. I don't spend much time in the Hearth Room, so yeah.
So why not restrict the inlet instead, i.e. install an Oak on the your BK and control that? Seems simpler maybe?
I've operated the Jotul 12 and Oslo and know it can be done with them under high draft. Not sure about the BK though.

What an incredibly cool house BTW!

 

[Diabel]

Interesting.

My local "useless" dealer that just started selling BK products said that if I install my new (potential) Chinook on a 25' chimney, BK might void the warranty due to the excessive draft.
He also said, if I run it through the wall and out on the side of the house, I will run into creosote issues and will also void the warranty.

Plus, he has never heard of a steel cat!! Chris, you might take notice.....

 

[webby3650]

Interesting.

My local "useless" dealer that just started selling BK products said that if I install my new (potential) Chinook on a 25' chimney, BK might void the warranty due to the excessive draft.
He also said, if I run it through the wall and out on the side of the house, I will run into creosote issues and will also void the warranty.

Plus, he has never heard of a steel cat!! Chris, you might take notice.....

Voiding the warranty may have been the wrong words, but his advice is sound.

 

[Ashful]

Voiding the warranty may have been the wrong words, but his advice is sound.

Pssst... webby, there is actually a statement in the owner’s manual that, “draft above 0.06” WC will void warranty.” However, I have never known BK to refuse support on this basis.

 

[webby3650]

Pssst... webby, there is actually a statement in the owner’s manual that, “draft above 0.06” WC will void warranty.” However, I have never known BK to refuse support on this basis.

I know, I was referring more to the tee system.

 

[Highbeam]

Pssst... webby, there is actually a statement in the owner’s manual that, “draft above 0.06” WC will void warranty.” However, I have never known BK to refuse support on this basis.

Bk has spoken up when errors are found in the manual or website and indicated intention to fix them. Notice that this 0.06” thing is not being deemed a mistake? Wtf? 15’ of vertical chimney required but only 0.06” allowed. Is this even possible without a key damper?

The “useless” dealer above knows that the warranty is void above 0.06” makes me think there might have been a dealer bulletin. That’s pretty excellent for any dealer to have noticed otherwise.

 

[Dieselhead]

FWIW I ran a key damper on my 26’ stack and it didn’t improve much, I actually took it back out. I was hunting down another issue but did have smoke smell with it in. That was on my former 2 season old door gasket though. Still get the faint sweet smell above the door if i have to much smoke in the box for the cat to process. I hope your results are different.

 

[Ashful]

Let’s be clear. I’m running two BKs, and have been for three years. I do NOT have a smoke smell issue, as long as I burn dry wood. The only time I have been able to generate smoke smell is when I burn wet wood.

 

[Ashful]

Wtf? 15’ of vertical chimney required but only 0.06” allowed. Is this even possible without a key damper?

I agree, this seems an impractical narrow range. However, I don’t think this is just BK, I think there are some industry/EPA testing standards upon which they’re leaning, here.

 

[kennyp2339]

I'm speaking of the 4-story job on the right, but you can also see the shorter chimney on my other Ashford on the left in this photo. Unfortunately, with 20" thick mud-stacked (not slang, the bedding mortar is literally mud from the back yard) stone walls all 'round, there's no chance of an OAK.

Problems on the west wing?

 

[Ashful]

Problems on the west wing?

That's the south wing, actually. It doesn't roll off the tongue as nicely, but that's what it is.

 

[semipro]

there's no chance of an OAK.

I don't think I made myself clear but the real problem is in accepted terminology.
I was not suggesting you install an "outside air supply'.
I was suggesting you install whatever fitting is needed on the stove to connect to an outside air supply (typically called an "outside air kit") and that you restrict the airflow going into the stove from inside your house with some sort of adjustable restriction at that fitting.
I am not suggesting you need to bore a hole in an outer wall.
I know this works in overdraft situations because I've done it with our Oslo

Edit: the fitting at the arrow below. .

 

[Ashful]

Thank you, @semipro. That might be something to consider, and you're right, I was misunderstanding you.

In related news, the key damper, manometer, and probe thermo are now installed:



So, now... well, chit. What do you do when you have the key damper completely closed, and your chimney still pulls harder than 0.06" on a partial load of four small splits?

 

[semipro]

What do you do when you have the key damper completely closed, and your chimney still pulls harder than 0.06" on a partial load of four small splits?

Restrict the flue outlet using some sort of chimney cap - perhaps a cable operated one?

My suggestion of restricting the stove inlet would only increase the flue vacuum but it may lower actual flow rate. It kind of depends on whether you'r trying to reduce flow rate or vacuum. I understand that BK has related warranty issues with the latter.

 

[brenndatomu]

What do you do when you have the key damper completely closed, and your chimney still pulls harder than 0.06" on a partial load of four small splits?

After that damper is in there for a while it will soot those holes up and work better for ya...BTDT...

 

[Sodbuster]

Restrict the flue outlet using some sort of chimney cap - perhaps a cable operated one?
View attachment 221940

My suggestion of restricting the stove inlet would only increase the flue vacuum but it may lower actual flow rate. It kind of depends on whether you'r trying to reduce flow rate or vacuum. I understand that BK has related warranty issues with the latter.

Not keen on that one, I know they default to "open" but chit happens.

 

[Easy Livin’ 3000]

Thank you, @semipro. That might be something to consider, and you're right, I was misunderstanding you.

In related news, the key damper, manometer, and probe thermo are now installed:

View attachment 221936 View attachment 221937 View attachment 221938

So, now... well, chit. What do you do when you have the key damper completely closed, and your chimney still pulls harder than 0.06" on a partial load of four small splits?

Pull the 6" liner and reinstall a 4 or 5"? Think of all that extra room you'll have in the chimney! Plus, nothing is more fun than climbing on top of that pitched roof, say, about 40' up off the low side?

That 30' insulated 6" liner will sell easily on Craigslist, long as it's not too banged up from it's experience.

 

[bholler]

Thank you, @semipro. That might be something to consider, and you're right, I was misunderstanding you.

In related news, the key damper, manometer, and probe thermo are now installed:

View attachment 221936 View attachment 221937 View attachment 221938

So, now... well, chit. What do you do when you have the key damper completely closed, and your chimney still pulls harder than 0.06" on a partial load of four small splits?

Put a second damper in or reduce the size of the holes through the damper