Overdraft on an insert. How do you deal with this?

[FyreBug]

Hi guys, I hope to garner some accumulated 'wisdom' with this situation. Someone recommended to weld or place a 1" or 2" piece of metal in the flue to restrict the air flow.

Also, If the unit has a 'pilot' (typically inside the firebox, just below the door a few small holes to aid in fire startup) blocking it with foil will also help.

Do you have any other suggestions that has helped you in the past?

 

[begreen]

If there is a damper, closing it can help, but not always with a strong drafting flue. Closing off the secondary port can help too. But the best suggestion is to avoid overfiring the stove in the first place.

One can reduce the air intake with some aluminum foil, but with great caution. If it is closed off too much it can result in snuffing out a hot, starting fire. That can lead to the rapid buildup of unburnt gases in the firebox. If these gases reignite, there can be a massive puffback. Under the best conditions this will necessitate a change of underwear. Under the worst it might damage the stove. For sure it will test every connection on the system.

 

[Stump_Branch]

Would this be the prime example of needing to run the draft calculation, ir have a water column test to determine flue size.
Personally, a piece of scrap metal would make cleaning a bear. I would say if the chimney is overdrafting steppung down a flue size may pencil out. The math isnt really all that hard just a touch of common sense needed.
Second thought would be a barometic dampner..one of those automatic ones..opens draws in cooler air..slows draft..

 

[mellow]

Man that is a good question, on these taller chimneys they can really "suck". And putting a damper on an Insert is about impossible. I know my 25 foot insulated liner gets quite a bit of vacuum going when it heats up, to deal with this I bring the kaowool a bit closer to the front top of the baffle to help slow down the exhaust a bit and reduce some of the vacuum that enters in the stove via the liner.

I have not seen any harm in this,buildup of creosote or blow backs, I could probably raise it even more to try and extend my burn times.

 

[FyreBug]

Would this be the prime example of needing to run the draft calculation, ir have a water column test to determine flue size.
Personally, a piece of scrap metal would make cleaning a bear. I would say if the chimney is overdrafting steppung down a flue size may pencil out. The math isnt really all that hard just a touch of common sense needed.
Second thought would be a barometic dampner..one of those automatic ones..opens draws in cooler air..slows draft..

The problem is a baro for an insert with a liner is very difficult, unless you know a way to do it?

 

[laynes69]

I wouldn't run a baro for theres no way to access it. Placing a ring to reduce the draft will cause problems in the mild seasons where draft won't be as strong. Having a way to slightly reduce the primary and secondary air intake when draft is at it's highest would be the best option. If a ring is placed in the flue when that door is opened, it won't have the draft needed and smoke could spill. Reducing air intake allows for full draft when the door is opened. Being an insert there's very little that can be done.

 

[laynes69]

Judging on your videos of your insert, your fire looked like ours on our furnace with over a .1" draft speed. We set our baro with .05"-.06" it's a beautiful lazy fire. A huge difference.

 

[FyreBug]

Yeah, that's what I think too. I wish I had a better answer to customers who call us about this. We see this issue once in a while and I was hoping somebody had figured out something that I wasn't aware of.

Maybe something a MFG could come up as an add-on to inserts would be the ticket. Not sure how much of a problem it is out there.

 

[begreen]

The problem is that you are dealing with a wide gamut of customers and woodburning experience. There are things I might suggest to a careful veteran that knows what to watch for. But I probably would not suggest the same to a novice. It takes time to learn the art of burning wood. Some folks are a lot more attentive than others.

 

[laynes69]

Your talking basically of the Florida Bungalow Syndrome? Something that a dealer or installer could add would be great for those with tall chimneys and bad overdrafts. Are the stoves, inserts, furnaces, etc. tested on tall chimneys just to see how they perform? Even then when in the field, theres too much variation. Maybe incorporate this in testing to simulate real life performance?