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Grind Slowly Moudre Fin in Stanbridge East

Detailed below is the combination of a contraflow takka with bell captivation chamber in the Empire Loyalist settlement of Stanbridge East

The one and a half story house which was built in 1897 from brick made in the village, rests upon a 6 foot deep basement formed by 2 foot thick stone walls. It has been known, until now, as notoriously cold.

It should be noted that the builder of the house was of Huguenot decent, his ancestors leaving France for America during the Wars of Religion, and then fleeing the newly formed United States for Quebec after the American Revolution.
His name was Charles Manly Blinn. His great grandson and local legend, Pumpkin Blinn, still lives across the road.

The objective would be to build a stove on the first floor that would also keep the basement above freezing point without using electricity, or an auxiliary RWA.

Building a contraflow with side channels that extended into the basement was an option, but this would have necessitated two sets of manifolds, one in the basement and a second in the usual position at the bottom of the stove in order to allow the employment of a bypass directly into the chimney. Also there would be a lot of mass, in an area where it was of little benefit, considerable friction from the channel walls, and way less available surface.

The final plan was to build a standard contraflow stove that would, as an alternative to flowing directly into the chimney, be drawn into a captivation chamber below the stove, in the basement, and then into the chimney. The captivation chamber would have the same footprint as the stove and its foundation, and occupy the top 3 feet of the 6 foot high foundation. The bottom three feet of the foundation would be an ash dump.

Throughout the text the captivation chamber will be referred to as bell.

a - Chimney
b - Firebox
c - Bypass Damper
d - Captivation Chamber
e - Tube allowing ash to fall through the captivation chamber
f - Concrete foundation slab
g - Footing
h - Floor level
i - Basement floor
j - Shutoff Damper
k - Ceiling
l - Block Foundation
m - Ash Dump

a - Chimney
b - Firebox
c - Bypass Damper
d - Captivation Chamber
e - Tube allowing ash to fall through the captivation chamber
f - Concrete foundation slab
g - Footing
h - Floor level
i - Basement floor
j - Shutoff Damper
k - Ceiling
l - Block Foundation
m - Ash Dump

The basement before restoration. To preserve the originality of the building, the basement walls would not be insulated, ether from the exterior or interior. There are 4 feet of the basement below grade and 2 above.

The stove and chimney will rest upon a 12 inch thick reinforced 35mpa concrete footing.

The three courses of block that form the ash dump, and the framing for the slab on which will rest the bell.

The outer wall of the bell and the chimney are built upon the foundation. The connection from the bell to the chimney is at bottom left, and the primary entry to the chimney above. The four square openings in the walls will allow access to the bell for cleaning and inspection. The square opening in the floor is to the ash drop.

The slab that will support the stove will rest upon the outer wall of the bell. The corners are turned, or filled, with half brick, to add more stability and compressive resistance. The fourth corner at bottom right is not turned or filled as this would potentially obstruct the opening from the stoves manifold to the bell.

A single sheet of 400g fibre glass mat is used as a gasket between the outer wall and the liner. The gasket is doubled on the corners. The liner is of 100 year old recycled mechanically pressed brick of Scottish origin layed in refractory mortar.

The completed liner and down-channel. Note that the liner is 3/8^ths lower than the outer wall. This avoids the slab that will be cast onto the bell, contacting the liner, allowing the liner to remain free floating.

View of the down-channel and its openings into the bottom of the bell.
It was decided to abandon this down-channel in favour of two openings at the top of the bell. The channel would have conveyed the gasses to the bottom of the bell, but its walls and added corner may have slowed down the stream to the point where combustion efficiency would begin to drop.
By removing the down-channel the risk of drag from it would also be removed. With out-channel hot gasses would be drawn in to the upper portion of the bell and cooler gasses drawn out from the bottom. Concerns were that the inflow may disrupt the free gas movement within the bell, and that the bottom of the bell would be abnormally cold.

N. Senf and A. Chernov were consulted upon this.

The channel has been removed and a 5 inch ID stainless steel section of pellet stove flue pipe, inserted into the opening to the ash dump. The pipe will convey the ashes from the stove through the centre of the bell to the ash dump.

The red tape on the forms reduces water loss during curing of the concrete, and makes de-forming easier and cleaner.

The wool gasket is placed upon the upper surface of the liner and the opening covered with a sheet of cement board. The cement board is cut only 3/8 ^ths larger all round than the dimension of the liner. This gives about 1/4 inch of cement board that rests upon the edge of the outer wall, leaving a maximum of the upper surface of the wall for the pour to contact directly. The wooden support 'T' will stop the cement board sagging and contacting the inner edge of the liner. It can be removed via the ash dump access opening.

Expanded polystyrene is used to make two forms for the openings in the slab. The large rectangular form to the right will give an opening in the floor of the rear manifold, and the square form to the left, an opening in the floor of the adjacent side manifold. The 5 inch ID tube to the ash dump is gasketed with ceramic wool.

Note: The slab was armed with 5/8 ^ths re-bar before pouring.

The de-formed slab.

The cuneiform protrusion of the slab beyond the walls of the bell in the basement.

The base course of the core. A 6 x 6 inch bypass and section of 6x6 flue tile connect the stove directly from its side manifold to the chimney.
With the bypass open the stove will draw directly into the chimney. With the bypass closed the stove will draw down and through the bell before entering the chimney via the connection from the bell to the chimney.

The bypass was installed to avoid the risk of the bell not drawing, or drawing slowly, and to use during start up if necessary.
These variables are not always easy to predict so installing the bypass can potentially save a lot of trouble.

The manifolds, and illuminated openings to the bell.

The finished stove: The brick are recycled from c. 1900, the relief brick c. 1840.
The stone Ducharmes Rose Arcenciel, Tiles c. 1910 are of Belgian origin.
Hardware by Upo.

The stone capped expanded skirt of the stove rests upon the protruding cuneiform fins of the foundation slab.
Note the pull rod of the bypass is in the open position.

The bell captivation chamber in the basement.

The fire can be started, with the bypass closed, i.e. bell engaged, if lit from the bottom. If the fire is lit from the top it burns better with the bypass open until it becomes well established. Once established the smoke will draw through the bell without problem and the bypass can be closed.
The walls of the bell and the slab on which the stove rests are relatively warm. The lower portions of the bells walls are cool.

This is a simple extended smokepath, that has the same footprint as the heater and chimney, and can be incorporated into the upper portions of an otherwise void foundation.
The bell captures heat not absorbed by the stove, and so will never heat the basement as would a stove. It is though, a heat source in the basement , which combined with the ambient heat of the floors above, has so far kept the basement relatively warm and dry.

Marcus Flynn

2012

Articles by Marcus Flynn

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