Is insulated liner necessary?

[EbS-P]

What can I do to combat the draft?

It is possible to install a damper in the appliance connector. There is a thread where the member used a socket u joint is used to extend it through the surround. Not sure how one would add two dampers on an insert. Probably one would seal off the holes present in the first damper and hope you didn’t need a second.

 

[brenndatomu]

A pipe damper needs to be opened fully before opening the door to load, and then closed/readjusted again after loading

 

[EbS-P]

It this something the install can do. How does that work is it in a permanent position? or would it need to adjusted from time to time.

Theoretically it wouldn’t have to be adjusted and could be set an left alone. But that has not been my experience. I got smoke rollout with it 85% closed so I would open to reload. I don’t have a lot of burns with it installed maybe 10 loads. I think I was

 

[begreen]

2 dampers on an insert are unlikely. A single one will be enough challenge for an installer.

 

[stoveliker]

Hard to do indeed (though there are cases where the damper is higher up, and operated thru the wall of the chase), but possibly needed for 35' of chimney...

 

[bholler]

Hard to do indeed (though there are cases where the damper is higher up, and operated thru the wall of the chase), but possibly needed for 35' of chimney...

I don't see how you could possibly install an inline damper up above the old fireplace damper opening. And even if you could servicing it later would be next to impossible

 

[BKVP]

I don't see how you could possibly install an inline damper up above the old fireplace damper opening. And even if you could servicing it later would be next to impossible

You're spot on. What a pain to sweep with that obstruction.....

 

[mellow]

You're spot on. What a pain to sweep with that obstruction.....

If the OP went with a BK insert with the 35 foot chimney what would be your recommendation? Have you seen someone transition from 6" to 8" with such a tall install to reduce draft?

 

[stoveliker]

Yes, it'll be a pain to sweep. I have seen pictures of 2 dampers, one in the collar and one thru the wall in front of the flue.

I do think the pain to sweep should be compared to the pain of having to clean your combustor from clogging fly-ash each burn, from having a draft that should make you careful to split your wood large enough so that not whole pieces of wood fly up the chimney through the bypass. Of course this is tongue-in-cheek, but 35 (or 38?) ft of chimney is not workable, and it's quite debatable whether one bypass will be sufficient.

The pain of fighting against a suction monster each and every burn may be worse than the pain of sweeping the thing once a year.

Installations differ, and people will have other opinions. This is mine. A warned person counts double (is a saying in the old country I'm from).

 

[bholler]

Sweeping past a damper isn't an issue at all with a rotary cleaner I do it all the time. Replacing a wornout damper up inside the chimney is a completely different story. And yes they absolutely do wear out

 

[BKVP]

If the OP went with a BK insert with the 35 foot chimney what would be your recommendation? Have you seen someone transition from 6" to 8" with such a tall install to reduce draft?

There are plenty of our inserts on 30' stacks without dampers being used, no complaints. I'm certain there are a few in NWT that have our units on 30' stacks (stoves more likely than inserts) and the thermostat handles them just fine.

 

[begreen]

There are plenty of our inserts on 30' stacks without dampers being used, no complaints. I'm certain there are a few in NWT that have our units on 30' stacks (stoves more likely than inserts) and the thermostat handles them just fine.

The OP is talking about an insert on a 26% taller flue system than 30 ft. I suspect that if tested they would be operating well beyond the target spec of .05wc. unless the insert is in a negative pressure zone.

 

[BKVP]

The OP is talking about an insert on a 26% taller flue system than 30 ft. I suspect that if tested they would be operating well beyond the target spec of .05wc. unless the insert is in a negative pressure zone.

More than likely...

 

[bholler]

There are plenty of our inserts on 30' stacks without dampers being used, no complaints. I'm certain there are a few in NWT that have our units on 30' stacks (stoves more likely than inserts) and the thermostat handles them just fine.

Yes but what happens when a door gasket gets just a little compressed? In a stove that has proper draft it wouldn't be an issue at all. In a stove that could easily have 3 to 4 times the specified draft it turns into a problem very quickly. Same with glass gasket bypass gasket etc. Can it pull through the ash plug?

 

[EbS-P]

The OP is talking about an insert on a 26% taller flue system than 30 ft. I suspect that if tested they would be operating well beyond the target spec of .05wc. unless the insert is in a negative pressure zone.

Yes but what happens when a door gasket gets just a little compressed? In a stove that has proper draft it wouldn't be an issue at all. In a stove that could easily have 3 to 4 times the specified draft it turns into a problem very quickly. Same with glass gasket bypass gasket etc. Can it pull through the ash plug?

At what length would one consider a smaller diameter liner?

 

[bholler]

At what length would one consider a smaller?

What do you mean by a smaller?

 

[BKVP]

Yes but what happens when a door gasket gets just a little compressed? In a stove that has proper draft it wouldn't be an issue at all. In a stove that could easily have 3 to 4 times the specified draft it turns into a problem very quickly. Same with glass gasket bypass gasket etc. Can it pull through the ash plug?

Sure enough. But that is why we use the knife edge seal to the front door gasket. The bypass is a cam over design constantly apply pressure. The glass gasket is a potential issue on any gasketed door. But, your point is valid. Too much draft is too much draft...

 

[EbS-P]

What do you mean by a smaller?

Diameter Edited original post

 

[bholler]

Diameter Edited original post

I will only consider it if allowed by the stove manufacturer. And it may or may not have the desired effect. Yes that will reduce volume but also increase velocity. I have put a reducer at the top with varying success because that restriction adds some back pressure at the top slowing things down in the chimney.

 

[Niro]

Just to be clear it's approx 35 to 38ft (I take an exact measurement this weekend) Would a smaller insert create less draft? Should I consider a smaller burn box?

 

[begreen]

The stove doesn't create the draft, the flue system does. The best bet may be to choose an insert that does not breathe easily (needs at least 16ft flue) and put a damper in the flue right above the insert.

 

[brenndatomu]

Would a smaller insert create less draft? Should I consider a smaller burn box?

Hot gasses rising up the chimney creates the draft...and that is what makes the stove work, not the other way around. The same stove on a 15 ft chimney vs a 25' can (will) act totally differently. Certain stoves do better on shorter chimneys and some do better with tall ones...almost none are gonna like over 30' (I know some manufactures say its fine, but you are still just asking for trouble)

 

[BKVP]

The difference between inside and outside temperature is what creates stack effect (draft). A positive draft helps fuel combust completely, in turn releasing hot gases into the stack. Preserving these hot gas temperatures has become more or increasingly vital to successful combustion as modern stoves have increased efficiencies. Often stoves without sufficient draft will experience charred, incomplete fuel pieces.

This is why draft increases when outside temperatures drop. Some of the best engineered/build quality stoves suffer in ultra cold regions such as Fairbanks.

Many stoves that have a hole in the bottom (or elsewhere), have metal plate that moves over the top of the opening in order to control the amount of air entering the firebox. It is the draft of the chimney that pulls that air into the firebox for combustion purposes.

In the 1970's and earlier, that metal plate could close-off the opening. Beginning with Oregon state emissions regulations, stoves needed a minimum amount of air on low burn rates....in order to meet standards.

As regulators lower the standards, even more air is needed. In most regions, having an opening that cannot be closed off, is less of an issue. (Unless you have an excessively tall chimney) However, it places with ultra low temperatures and correspondingly higher draft, even the best built stoves can be damaged. I've seen it many, many times.

Control mechanisms that limit draft have been employed for centuries.

These folks here are providing guidance for a safe, successful and rewarding installation.

BKVP

 

[BKVP]

As you can discover by reading test reports, posted under Federal law, to manufacturers websites, the use of a combustor enables lower (in terms of kg/h) burn rates. Secondary combustion stoves need 1176F to breakdown PM whereas chemical conversion via combustor begins at 550F.

Test reports may not be very good indicators (predictors) of consumer satisfaction, but at least they do show how slow or how fast a stove can burn fuel.

 

[mellow]

I have never had a chance to test this, but if going to a 5.5" liner increases velocity wouldn't the opposite affect happen if you go to an 8" liner?