coaly Hearth

Ted Garriott wrote:I have a grandpa Fishers wood stove. It does not have any type of plate in the top. All my smoke and heat go straight up the pipe. My question is is there supposed to be a plate in the top of my stove to divert the smoke and Heat

The Fireplace Series stoves before 1980 had no baffle.

The Smoke Shelf Baffle was designed by Fisher R&D to reduce smoke. It was added to the UL approved Series III stoves in 1980. These stoves will have Cathedral (arched top) doors, no angle iron corners, and a UL Label on rear shield.

The Insert had none, but has a adjustable damper. Grandma, Grandpa, XL, Goldilocks, and mobile home approved Honey Bear had the Smoke Shelf Baffle design baffle plate. The single door stoves of the Bear Series had a flat plate below outlet with no baffle plate.

Originally the stoves were designed to use the larger flue of existing fireplace chimneys. A baffle reduced the amount of heat loss up the flue causing creosote formation. With a liner the same size as stove outlet, preferably insulated, or an insulated metal chimney the same diameter as stove outlet, a baffle can be added. Flue temp must be monitored, and check frequently for creosote formation until you know how much you produce.

The baffle thread in Fisher Forum on Hearth is now stickied at top of Forum home page. I am the author.

https://www.hearth.com/talk/threads/simple-baffle-solution-for-your-old-fisher-more-heat-less-smoke-under-25.74710/

D Nikolls wrote:Neat, good to see the impact.

I have the impression that back-when, the baffle was thought of as 'slow down the escaping hot air', and now.it is thought of as 'let's make the combustion more complete'..


I wonder what you would see if you doubled up on baffles...

Have you thought about adding a secondary air intake?

The baffle was designed to reduce smoke. EPA rules went into effect in stages, and the baffle allowed production up until the last phase of regulation in 1988 when they didn’t reduce smoke particulate size enough. The particles collected went from 60 g for every kg of wood burned down to 6 with the factory Smoke Shelf Baffle in the double door stoves.

A baffle increases resistance within the fire box. A flue damper is a variable resistance that is used to slow an over drafting chimney. Every stove has a required draft measured at the flue collar. Doubling the path through stove increases the draft needed, so the chimney and connector pipe configuration becomes more important as well as using double wall pipe inside with the added resistance. There are calculations and the highest resistance is normally the air intake. More baffling slows the velocity allowing longer dwell time in stove, extracting more heat, causing condensing issues.

Fine line between how much you can remove before entering chimney. Only straight up, insulated flue the same size as stove outlet can operate with less heat. The main objective is staying above 250*f. all the way to the top. Below that critical temperature water vapor from combustion condenses on flue walls allowing smoke particles to stick. That critical temperature is only while smoke is present. You can see why manufacturers don’t double baffle not knowing what chimney and pipe configuration will be used on each stove. They have to err on letting more heat than necessary to prevent creosote formation.

Jordan Holland wrote:I have a Fisher Pappa Bear. I recall reading about them that they were designed not to need a gasket on the door. Mine did not seal as much as I wanted, so maybe the air leak was part of the design to add a little secondary air up higher than the dampers? The baffle was called an "ash fender," so my guess is it is designed to help prevent ashes from getting sucked into and blocking the horizontal area before the elbow. I've wondered about the possibility of making a small Walker-esque stove from it. Maybe some day...

The ash fender is the shelf under the door.

The baffle in the Fireplace Series, or double door stoves is patented as the Smoke Shelf Baffle.

The door seal was designed “air tight” with three sealing points all the way around. There is no clearance for gasket material. The center of the channel iron web contacts the raised portion of door and the edges of channel iron contact the back of door making the 3 points of contact. Cleaning the channel iron and door back is all that is necessary to seal. Worn door hinges or hinge pins cause air leaks. Glass door models use gasket material. When the doors were mounted, the stove was laid on its back and door centered on door sealing channel iron. The hinge plates were tacked in place and the door should lay flush against stove front. If the hinge plates were not exact, space exists at sealing area.

Actually, the Smoke Shelf Baffle was designed in 198O by Fisher research and development for reducing smoke. It reduced particulate from 60 grams of particles for every kg burned down to 6. It was only used in the double door stoves with 8 inch outlet since the 6 inch stoves were normally connected to existing chimneys that were much larger built for fireplaces. So slowing the rising gasses and not allowing as much heat up the larger flue would create creosote problems. With the advent of secondary burn stoves and most all requiring 6 inch flues, adding a baffle with correct sized insulated flue works fine. That’s why the single door Bear Series didn’t have the factory baffle.
Coaly