Fireplace

The invention relates to a heater which is connected to the flue of a house. The heater includes a firebox, an intermediate plenum chamber and an outer plenum chamber. Either atmospheric or ambient air is introduced into the heater and led over the heated surfaces of the two plenum chambers before issuing into the space to be heated.

The invention relates to a heater for circulating air. When considering 
home heating, and due to the extremely high cost of solid fuel, it is 
essential that the fireplace be efficient as possible. 
Most open fireplaces are inefficient where 90% of the air travelling up the 
chimney is heated air from the house being forced into the flue by 
convection. The amount of air actually required for combustion is only a 
fraction of this total volume and such air must be replaced in the house, 
usually through the intermediary of windows, doors and electrical outlets. 
The usual open fireplace, in effect then, creates a vacuum in the house by 
forcing such a large amount of air up the chimney that the heating 
efficiency of such fireplaces is, to all intent and purpose, nil. 
It is the object of the present invention, therefore, to provide a heater 
which will overcome the above disadvantages.

Referring to the drawings, the heater includes an upper portion indicated 
generally at 1 and a lower portion indicated generally at 25. The upper 
portion 1 includes a firebox 2, capable of receiving fuel, the front of 
which abuts a front plate 3 provided with a louvered vent 4 (not shown in 
FIG.2) and a pair of hinged tempered glass fronted doors 5. The upper part 
of the firebox 2 is frusto-pyramidal in cross-section and is provided with 
a smoke outlet 6. 
The firebox 2 is disposed within, but spaced from, an intermediate housing 
7 also provided with an orifice 8 with the space between said housing and 
the firebox defining a plenum chamber 9. A pair of primary flow chutes 10 
is provided within the housing 7, each one of which is located adjacent a 
side wall 11 of said housing 7. Each chute is defined by a said side wall 
11, a front wall 12, an inner wall 13 (See FIG. 2) and a rear baffle 14 
(also shown in FIG. 2). 
An outer housing 15 is also provided and this is disposed about, and spaced 
from, the intermediate housing 7 so as to define an outer plenum chamber 
16 between this pair of housings. The outer housing 15 is also provided 
with an orifice 17 and a dampered smoke chimney 18, controlled by damper 
19, passes through the orifices 17 and 8 as well as the smoke outlet 6 so 
as to connect the firebox 2 with the flue or chimney of the house. The 
outer housing 15 is also provided with an air inlet (not shown) in its 
bottom which inlet is in communication with the lower unit 25. 
A pair of vents 20 also connect the outer plenum chamber 16 to the firebox 
2, one on either side of the latter near the bottom front thereof, and 
these are each controlled by a damper 21. 
The lower portion 25 of the heater includes an air chamber 26 located 
beneath the upper portion 1 and in communication with the outer plenum 
chamber as well as with atmospheric (or outside) air and ambient (or 
inside) air. The chamber 26 communicates with atmospheric air through the 
intermediary of duct 27 (FIG. 2) and a hole 28 in the bottom of portion 25 
or hole 32 in the back of portion 25, (whichever is the most convenient, 
with the remaining hole being blanked off), and with ambient air through a 
pair of adjustable vents 29 located in the front of the lower portion 25. 
Hole 28 is provided with a damper 30. A fan 31 is also provided within the 
lower portion 25 and attached to the underside of plenum chamber 15. 
A heat sensing bulb 35 (FIG. 2) located in the upper portion 1, is 
connected to a capillary tube 36, extending through a tubular guide 37, 
which is connected to a thermostat 38 located in the lower portion 25. 
Thermostat 38 is connected to fan 31 via an electric supply line 39 as 
well as to a junction box 40 and from the latter, via line 41, to any 
suitable source of electrical supply. The inlet end of duct 27 is provided 
with a hinged, weighted damper 45 to inhibit reverse air flow. 
In operation, the upper and lower portions 1 and 25 of the heater are 
connected together to form one combined unit. After installation in a 
house and connection to the flue and when required for use, the operator 
opens the doors 5 and places any suitable solid fuel in the firebox and 
ignites it. Atmospheric air is then introduced into the lower portion 25 
and air chamber 26 via tube 27 and fan 31. It will be appreciated that if 
and when the fan stops, the weighted damper 45 will automatically close so 
as to prevent reverse air flow. The fan 31 then forces the atmospheric air 
up into the outer plenum chamber 16 and up the back and two sides of the 
intermediate housing 7, then over the top of the latter and down the pair 
of chutes 10 and into the plenum chamber 9, with the baffles 14 assisting 
in directing such air downwardly. The air then rises and passes over the 
outer surfaces of the firebox 2 before passing out through the vent 4 to 
the area or interior of the room to be heated. Obviously, the air during 
its passage through the outer and inner plenum chambers, will be heated. 
Air for combustion is introduced into the firebox 2 through the vents 20 
and which because of the dampers 21, restrict air flow when required. 
As will be appreciated, the doors 5 on the front of the heater must be 
sealed for the unit to operate efficiently. With these doors closed, air 
for combustion can be properly metered into the firebox 2 and all air 
passing through the heat exchange chambers will be atmospheric air or 
ambient air or a mixture of both. This is accomplished by adjusting damper 
30 to partially or wholly close off the avenue of atmospheric air and 
simultaneously opening vents 29 to allow ambient air to enter the plenum 
chambers. This arrangement provides an extremely efficient means of 
completely closing off outside air and reheating the inside air only when 
the outside air is too extreme for efficient heat exchange. Moreover, upon 
retiring for the night, if only inside air is being circulated then, once 
the fire burns out, any air still circulating through the unit by simple 
convection will be heated inside air and not cold outside air. The 
thermostat, 38, of course, prevents cold air being drawn into the house 
when the fire dies out. Hence, the house will be pressurized by the action 
of the fan drawing air into the house from outside when the glass doors 
are shut. Additionally, only sufficient air will be permitted to enter the 
firebox to support combustion. The amount of hot gases escaping up the 
flue or chimney is only a small portion of that from an open fireplace. 
On the other hand, if the doors are left open, the unit becomes a 
conventional inefficient fireplace or heatilator because the room air will 
just escape up the flue or chimney.