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Патент USA US2502346

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March 28, 1950
Filed Oct. 15, 1945
3 Sheets-Sheet 2
d N
March 28, 1950
Filed Oct. l5, 1945
007' DÚUR
77725911105 7A T
3 Sheets-Sheet 3
Patented Mar. 28, 195()
Frank A. Ryder, Chicago, lll., assigner to Stewart
Warner Corporation, Chicago, lll., a corpora
tion of Virginia
Application October 15, 1945, Serial No. 622,429
3 Claims. (Cl. 236-10)
The presentvinvention relates to heaters and
vmore particularly to heaters of the self-con
wardly as indicated by the arrows along the line
4-4 o1' Fig. 1. This view indicates the construc
tained floor furnace or space heater type. Al
tion of the heat exchanger and the orientation
though the heater shown is intended to be ñred
of the burner relative thereto; and
by fuel gas, it will be appreciated that the major
Fig. 5 is an electrical circuit diagram of the con
portion of the invention at least is equally appli
trol system for the heater shown.
cable to heatersvof the oil fired or even solid fuelY
'I'he heater illustrated, which comprises a pre
ferred embodiment o1' the present invention, has
It is an object of the present invention to pro
a generally cylindrical outer shell Ill secured at
vide `a small self-contained floor furnace type 10 its top to a flanged grill l2 adapted to be sup
heater which is economical to manufacture, and
ported by the flange from the ñoor Il of the room
which may be easily installed.
in which the heater is located. To accommodate
A further object of the invention is to lprovide
the heater, a circular hole is cut in the door
a novel heater of the above type which may be
and in order to simplify the problem oi.' installa
installed in either new or old houses with the 16 tion, the dimensions of the heater are such that
minimum of installation difliculty, and with a
it will ñt between standard joist spacing. Thus it
maximum flexibility of choice of location.
is not necessary to cut into the structural ele
Yet another object of the above invention is to
ments of the floor in order to locate the heater and
provide a novel heater and control system which
therefore no special bracing of the floor is neces
has the combustion side entirely sealed from the 20 Sary.
Ventilating side and in which no chimney is re
The exhaust from the heater is carried out
wardly through the side wall of the building
through a small diameter tube I6, which may be
enclosed within a coaxial tube I8 which also
with means for obtaining better and more even 25 passes through the wall of the building. The
temperature distribution of the heated air than
space between the tubes serves to convey air for
has heretofore been considered feasible in heaters
combustion from the outside of the building to
of the ñoor furnace or space heater type.
the heater through a U-shaped branch pipe 20.
Yet another object of the present invention is
To make the connection between the pipe 20
to provide a novel automatic heater control sys 30 and the tube I8, the inward end of the tube is
ñtted with a collar 22 sealed to the pipe IB and
Another object is to provide a novel heater
a branch spud 24 is secured to the pipe i8 and
which maintains a more even temperature in the
surrounds a generally circular opening 26 in the
space to be heated than can be accomplished by
tube. The connection is completed by securing
simple on-and-off thermostatic control means,
35 the pipe 20 to the spud 24 preferably at the time of
Other. objects and advantages will become ap
parent from the following description of a pre
The heat exchanger portion of the heater com
f erred embodiment of my invention in which sim
prises a vertically extending sheet 21 which is
ilar characters of reference indicate similar parts
bent to deep U-form to comprise an inner cham
throughout the several views.
40 ber 28, the upper portions then being rolled over
In the drawings:
at 30 and bent downwardly generally parallel to
Fig. 1 is a vertical medial sectional view
the first portion of the sheet as at 32,l and into
through a floor furnace embodying the present
a position opposite the center of the sheet. At
invention, illustrating the major components of
this point the two ends are welded together at
the heater and the construction thereof;
45 34. In order to stillen the structure, flanged U
Fig. 2 is a medial sectional view of a portion of
shaped spacers 36 are welded to the outer sur
the control mechanism illustrated in elevation in
face of the inner portion of the sheet, that is,
Still another object of the present invention is
to provide an improved heater of the above type
Fig. l;
the portion of the sheet bounding the chamber
Fig. 3 is a horizontal sectional view taken in
28 and have their opposite ends abutting the outer
the direction indicated by the arrows along the 50 portion of the sheet. The portion of the structure
line 3-3 of Fig. 2. Fig. 3 may also be considered
just described is located within an oval shaped
casing 38 comprised of two halves seam welded
together at (il along the medial line of the struc
ture. The shell 3B is in turn enclosed within an
Fig. 4 is a horizontal sectional _v_iew looking up- 5s oval outer shel1‘42 constructed generally similar
as a horizontal sectional view looking downwardly
as indicated by the arrows along the line 3a-~3a
to the shell 38 excepting that it is sumciently
The cylindrical casing I0 is divided vertically
larger to provide an annular space between the
by a partition 84 so as to provide space on one
shells 38 and 42. The spacing between the shells
side for the heat exchanger and burner just
is maintained uniform by a plurality of spacer
described and to provide a second space 88 on
elements 44 similar to the elements 36.
the other side which receives inlet Ventilating
The two ends of the portion of the heat ex
air and contains blowers and miscellaneous con
changer just described are closed by upper and
trol elements. In the lower portion of the cham
lower header plates 46 and 48 respectively which
ber 86 in a position generally below the burner
enclose a gas passage from the chamber 28
and heat exchanger, a vertical shaft 88 is jour
around through the annular space between the 10 naled to rotate in bearings 90 and 92. The
shells 32 and 38, the lower portion of this latter
upper of these bearings is supported upon a
space being connected to an exhaust tube 50
spider 94, the arms of which are secured to a
which is welded to the center of the sheet 38 in
blower housing 86. This blower housing is ar
a position opposite the seam 34. The header
ranged with an air inlet opening beneath the
plates have slots therein which register with 15 spider and this opening leads to the inlet of a
the slots in the heat exchanger in which are lo
sirocco type wheel 88 arranged within the usual
cated the spacers 36 and 44. The 'construction
scroll shaped case |00. The outlet of this scroll
therefore permits Ventilating air to be passed
shaped case |00 leads to a flange |02 having an
lengthwise through the heat exchanger between
opening in register with the same opening at
the casing 42 and the shell 88 and through the 20 the side of the plenum chamber 54. When the
U-shaped slot between the upwardly and down
shaft 88 is rotating, air is drawn inwardly
wardly extending gas passages- 28 and 52, re
through the portion of the grill I2 above the
space 86 and passes downwardly into the sirocco
The lower end of the heat exchanger is con
wheel 88 and into the plenum chamber 56. From
nected to receive Ventilating air from a formed 25 here the air passes upwardly through the passages
sheet metal plenum chamber l54 adapted to re
in the heat exchanger into the space between
ceive Ventilating air from a blower, as will be
the heat exchanger and the grill I2. From this
presently described.
This plenum chamber is
chamber the air passes outwardly through the
grill to the space to be heated.
sages previously described so that air passes into 30
Directly beneath the scroll case 96 and formed
the heat exchanger at the bottom and out at
integrally therewith is a second scroll case i813
the top.
having its air inlet |06 at the lower surface
The burner comprises a generally cylindrical
thereof. The inlet opening |06 is connected to
tube 56 somewhat longer than the heat exchanger
an elbow |08 which passes through the side of
which has a plurality of outlet jets 58 arranged
the case I0 and is connected by means of match
in communication with the Ventilating air pas
along one side, the total length occupied by the
jets being something less than the overall length
of the heat exchanger. The tube 66 is closed
ing flanges ||0 with the combustion air inlet
pipe 20.
at its upper end and is provided with a bell
means of a pair of matched flanges H2? to a
mouth 60 at its lower end. This tube extends
vertically within the heat exchanger in a posi
tion closely adjacent the central portion of the
sheet 21 with the jets pointed toward the mouth
62 of the chamber '28, that is, at the point at
which the sheet 28 is rolled over as at 30.
The bell portion 80 of the tube 56 is enclosed
within a combustion air plenum chamber 64
formed by a flanged cup 66 which is sealed as
by welding to the lower header plate 48. This
cup has an opening 88 considerably larger than
the tube 56 through which the lower portion of
the tube extends. The combustion air plenum
chamber 64 therefore >delivers air both through
the opening 68 into a position around the jets
58, and also to the bell mouthed opening 80 of
the tube 56.
Gaseous fuel is brought into the heater
40 Venturi section ||4 which in turn leads to an
The outlet of the scroll case |04 is secured by
elbow ||8 connected to the combustion air
plenum chamber 64.
With the above arrangement it is apparent
that whenever the sirocco wheel 98 is operating,
45 the combustion air blower wheel ||1 secured
to the lower end of shaft 88 will also be rotating
and will draw air inwardly through the annular
space between the tubes I8 and I6, through the
pipes 20 and |08, and will pass this air outwardly
50 through the Venturi section ||4 and elbow || 6
to the combustion air plenum chamber 84. From
here a portion of the air is aspirated by the gas
nozzle 18 so as to form a rich mixture which
passes inwardly through the burner tube 58 and .
55 out into the combustion chamber by Way of
through a pipe 10, through a gas pressure con
the nozzles 58. Another portion of the combus
tion air passes from the plenum chamber
through the opening 88 and mixes in the heat
trol valve, indicated generally by the numeral
exchanger with the rich mixture issuing from
12` and from the valve through a magnetic shut 60 the jets. This mixture is ignited by the spark
off valve 13 and pipe 14 to a nozzle 18 having
plug 18 and the hot products of combustion pass
its open end position within the bell 60 so that
out through the mouth 82 of the -inner chamber
gas ñowing from the nozzle 16 will inspirate
28, around through the side passages, and out
air to provide a rich mixture of air and gas
wardly through the exhaust fitting 50 to the ex
which burns after it leaves the jets 58, because 65 haust pipe |6 to which the latter is connected
of the presence of secondary air introduced
by a pair of mating flanges H8. From the ex
through the opening 68. Ignition is accomplished
haust pipe |6 the products of combustion pass
by means of a spark plug 18 secured in a bushing
outwardly to the air through the wall oi' the
80 welded to the upper header plate 48 in a po
sition adjacent ~the uppermost of the gas outlet 70 The blower shaft 88 is driven by an electric
jets 58. Convenient support for the burner tube
motor |20, the power transmission being by way
l56 is provided by welding the upper end of this
of pulleys |22 and |24 and belt |26.
tube to the upper header plate 48 and by secur
In order to make the unit extremely easy to
ing the lower end to the wall of the combustion
install, it will be noticed that the flange ||8 at
75 the end of the exhaust pipe 50 and the flange Hl
air plenum chamber 66 by a bracket 82.
at the end oi' the elbow |08 arey recessed in de-`
pressions |28 and |30,'respectively, in the side
upper portion ofthe intermediate casting |50
provides- a circular opening of considerably
wall of the case |0 so that the entire heater can
larger diameter |56 which is similarly matched to
be lowered through the opening in the iloor I4
without the necessity for cutting special openings
to clear these flanges. ‘ Similarlythe motor‘and
its bracket |32 can be attached to the heater and
the belt |26 located upon the pulleys after the
heater has been lowered into place. Actually the
motor is shown in the position illustrated merely
for clarity of illustration. It is preferred that
this motor be located inside the space ,86 at
an opening in the lower surface |58 of an upper
approximately right angles to the position shown
so that the entire mechanism can be located
within a single housing prior to installation.
The control system for the present heater com
prises a simple relatively low cost arrangement
such that the heater can be fully on at a high
heat position while the'space is being heated from
an originally low temperature or whenever such .
a large amount of heat is needed. After the tem
perature reaches approximately 68°, the heater is
automatically cut down to a low heat range
where it stays unless either the room cools down
suillciently to require full heat, or unless the 25
temperature in the room continues to rise, in
which latter event the heater is shut ofi at about
70°. The heat output at the low heat position is
not constant but depends upon the temperature
casting |60. A diaphragm |62 of material similar
to the diaphragm |54 is clamped between the
castings |60 and |50, the castings being held
together by screws |64. The diaphragm |62
therefore serves to isolate the space |58 from the
space |56.
The diaphragms |62, |54 and the poppet valve
|48 are all secured to an axially movable valve
-stem |66 which extends centrally through the
device and is secured at each end to a soft acting
spring |68 which together serve both to urge the
valve stem | 66 in an upwardly direction `with very
light pressure, and also to position the valve stem
axially of the device and resist radial movement.
As shown in Fig. 3, each of these springs con
sists of a disc of very thin sheet metal having
openings |10 cut therethrough so as to leave a
hub |12 at the center for attachment to the stem
|66 and narrow arms |14 spiraling outwardly to
theperipheral portion of the disc. The springs
|68 are clamped against the ends of the castings>
| 38 and |60 by dish shaped covers |15 and gaskets
|11, secured by screws |19. Each of the dia
phragms |54 and |62 is stiffened at the central
portion by plates |16 which restrict ñexure of the
of the outside air so that whenever the ambient 30 diaphragm to the peripheral portion between the
temperature is low, the heat produced in the low
plates and the cast housing.
heat position is automatically higher than the
The intermediate chamber |56 is connected by
amount of heat produced in the same position
means of a threaded opening Ij'lilA in the casting
under more temperate conditions.
|50 to a fitting |80 leading to a tube |82 which in
'I'he heater also includes mechanism for shut 35 turn is connected by a iltting |84 to the throat
ting oil.' the ñow of fuel if combustion does not
of the venturi | I4. Similarly the upper chamber
start within approximately 45 seconds, and for
|58 is connected by way of a threaded opening |86,
preventing further operation of the heater until
fitting |88, and tube |90 to a fitting |92, which
this control has been manually re-set. In addi
extends through the side wall of the elbow ||6 in
tion, if the room temperature rises above 70°, the 40 a position slightly downstream of the venturi and
heater will not return to operation until the
is curved so as to form a ram |94 facing into the
temperature has dropped below the low heat
stream of flowing air.
range and thus, the heater always starts in the
The operation of this portion of the device is
high heat position.
as follows: Whenever the speed of the blower is
All of the above is accomplished by relatively "increased, a greater quantity of air is forced
simple means shown in physical outline in Fig. 1.
through into the combustion air plenum chamber
The construction of the gas regulator is shown
64 and thence to the burner. This greater quan
in greater detail in Fig. 2, while Fig. 4 illustrates
tity of air requires more fuel in order to maintain '
the electrical circuit. The wiring in Fig. 1 has
a proper fuel-air ratio and this increase in fuel
been deleted in the interest of clarity of illustra 50 flow is provided by the gas pressure regulator 12 . '
in the following manner. As the flow rate through
The gas pressure regulatory illustrated in Figs.
the venturi ||4 increases, the pressure at the ilt
2 and 3 comprises a lower chamber |34 formed
ting |84 will be decreased while the pressure at the
in a casting |36 w'ith a threaded opening |38 to
small ram |94 will increase. Since these two
receive the inlet gas pipe 10. This chamber is 55 fittings are communicated to the pressure regu
separated from an upper chamber |40 by a parti
lator by way of pipes |82 and |90, respectively,
tion |42, which has a centrally located vertical
the result is that the pressure in the intermediate
threaded opening |44 therethrough into which is
chamber |56 is decreased, while the pressure in
ñtted a valve seat |46. This valve is closed on
the upper chamber |58 is increased. This in
its lower side by a poppet type valve |48' so that 60 crease in pressure differential across the dia
whenever the valve is depressed,.gas can pass
phragm |62 causes the diaphragm to tend to urge
from the chamber |34 around the valve |48
the valve stem- |66 downwardly, thus opening the l
through the valve seat bushing |46 into the , poppet valve |48. The gas flow from the pipe 10
chamber |40 and thence to a gas outlet'pipe 14
to the pipe 14 is therefore at a greater rate and
communicating with the upper chamber |40.
the gas pressure in the chamber |40 will rise until
The upper face of the casting |36 is flat and
the gas pressure against‘the lower surface of the
matches the lower face of an intermediate casting
diaphragm |54 is suflicient to return the valve to
|50. The inner wall of the lower casting |36 at
equilibrium. In other words, any increase in the
the upper end is so shaped that the chamber |40
pressure differential across the upper diaphragm
at this point forms a circular opening which
will be accompanied by a higher gas pressure and
matches a similar opening in the casting |50.
`the gas pressure will rise until the force of the
These two castings are secured together by means
gas pressure acting upwardly on the lower dia
of screws |52 and clamped between them is a soft
phragm |54 equals the forces produced by the
flexible gas impervious diaphragm |54 which
difference in air pressure acting upon the upper
forms the upper closure of the space |40. The 75 diaphragm |62 and the lower diaphragm | 54.
It will be noted that the low pressure in the
intermediate space |56 operates on both the dia
phragms |54 and |62, but since the upper of these
dlaphragms has greater area, the net effect is
to produce a force equal to thepressure operating
220 and the lead 224 so that this valve is energised
against a diaphragm having an area equal to the
at the same time as the motor |20. The heater
coil 2|1 in the safety control 2|8 has one of its
ends connected to the wire 220, while the other
end is connected by way of lead 284 to a terminal
236 of a single throw double pole flame detector
area of the larger diaphragm minus the area of
the smaller.
end of the primary 240 of a step-up spark trans
It is apparent, therefore, that the heat output
of the heater can be increased by increasing the
voltage drop across the electric motor |20 since
this will cause a higher blower speed both of the
combustion air blower and the Ventilating air
blower. As it has been explained previously, an
increase in the speed of the combustion air blower
causes a greater ñow of both air and gas to the
heater and, therefore, a higher heat output rate.
At the same time the increased speed of the ven
tilating air blower 98 supplies a larger quantity of
'I'he terminal 236 is also connected to one
former 242, while the other end of the primary is
connected by way of lead 244 to the line 220 be
tween the motor |20 and the safety switch 2 I8.
The iiamedetector 238 is of the type having
contacts which are closed when the device is
cold and in which the contacts open within about
|5 to 80 seconds after combustion starts. As
mentioned previously, this detector is oi' the
double pole single throw type in which both
switches of the double throw combination are
` opened and closed at the same time.
The con
Ventilating air to carry away the additional heat. 20 tact 246 in the device, which operates in con
The electrical system, which is intended for
junction with the contact 288, is connected 'to
operating on an alternating current circuit, com
thi side of the line represented by the lead
prises a step-down control transformer 200 con
22 .
nected by way of a plug and cord 202 to an outlet
Of the other set of cooperating contacts in
box 204 or other source of electrical energy. One 25 the flame detector, one of these, 248, is connected
side of the high voltage side of the line is con
to a line 250 leading to one end of the coil 252
nected by way of a lead 206 to a normally open
in the relay 2|0, the other end of this coil being
contact 208 in a relay 2 I0. The cooperating con
connected to one side 254 of the control trans
tact 2|2 is connected by way of the line 2|4
former 200. -'The other contact 256, which co
through a normally closed over-heat limit switch 30 operates with the contact 248, is connected by
2|6 to a latch open type safety switch 2I8. The
lead 258 which extends to one of the contacts
over-heat limit switch may be of the conventional
260 in the room thermostat 262.
bimetal type and is located in the space above the
The room thermostat is of the double pole single
upper header plate 46 in such manner that if
throw type with the temperature differential be
for any reason Ventilating air becomes shut off, 35
tween the two sets of contacts such that as the
such as by someone placing newspaper, a pillow
temperature rises, the contact 260, previously
or some such object over the grill |2, the increase
is separated from its cooperating con
in temperature of the bimetal element will cause
tact 264 at a temperature of approximately '10",
the electric current to be interrupted.
The latch open type safety switch may be ar 40 while the other two contacts 266 and 268 are sep
arated upon a rise in temperature to about 68°.
ranged with one contact secured to a bimetal
The thermostat contact 264 mentioned as co
strip in such manner that heating of the strip
operating with the contact 260 is connected by
causes the contacts to separate. This bimetal
lead 210 to the opposite side 212 of the control
strip is in turn provided with an electrical heating
transformer 200, this side of the transformer also
element 2 I 1 which can receive current for a short
being connected by lead 214 to the contact 266
interval at starting in a manner to be explained
in the room thermostat. The contact 268 which
presently. The switch is so timed that approxi
cooperates with contact 266 is connected in turn V
mately 45 seconds of heating is required before
by way of lead 216 to the coil 218 of a normally
the contacts separate. As a further safety pre
open relay 280, the opposite end of this coil be
caution the switch is so arranged that once it has
ing connected in turn by way of lead 282 to the
opened, it latches in the open position and will
side of the control transformer represented by the
not return to circuit closing position until man
lead 254. The set of contacts 284 closed when
ually re-set.
the coil 218 is energized are shunted across the
The latch open type switch 2|1 is connected in
turn by way of a lead 220 to the fan motor |20, 58 reactance 222 and resistor 226 by way of leads
286 and 288.
the opposite terminal of which is connected
As explained, the relay 2 | 0 is of the double pole
through a series reactance 222 to the other side
single throw type. The set of contacts in this
of the line indicated in the drawings by the wire
relay not previouslyy mentioned are indicated by
224. The resistance of the motor |20 and re
actance 222 together can be altered by means of 00 the numeral 280 and are bridged across the leads
a variable resistor 226 shunted across the reac
The resistor slider is mechanically con
nected to an expansible bellows element 228 which \
Y 250 and 258.
One lead of the secondary 292 of the spark
transformer 242 is connected to one side of the
spark plug 18, while the other sides of the spark
perature sensitive bulb 232 located in the combus ß plug and transformer secondary are grounded
in the usual manner.
tion air inlet duct 20. The connections to the
The control system above described operates
resistor are such that an increase in temperature
in the following manner: Assume for the moment
of the incoming combustion air will cause an
that the heater has been turned oil, such as by
expansion of the gas or vapor in the bulb 232
thereby causing an elongation of the bellows 228, 70 the opening of a switch (not shown) in the main
and this -elongation in turn operates to increase
line 202, and that the temperature is below 68°,
and further that the heater has been ofi' sutil
the resistance across the reactance 222 so as to
communicates through a tube 230 with a tem
increase the resistance of the system as a whole.
' ciently long so that the flame detector has cooled.
The fuel system magnetic shut-off valve 13 pre
Under the above conditions, the control system
viously referred to is connected between the line 8l is characterized by the following features. The
2,502,345 `
contacts 2|2 and 208 in the relay 2|0 are sep
arated, as are the other set of contacts 290, in
this same relay. The room thermostat contact
points 260‘and 264 are closed as are the contacts
2'66 and 268. Contacts 284 of the relay 280 are"
ation. Separation of the llame detector contacts
. 236 and 246.deenergizes the heating coil 2|1 withk
the result that the safety switch 2|8, which has
been heated for a period of from 15 to 30 sec
onds; now starts cooling and cools back to am
open whilethe contacts 236 and 246 and 256 and
bient temperature without the contacts in this
248 of the 'flame detector are closed. Similarly,
the over-’heat ylimit switch 2|6 is closed as are
switch ever having been separated.
As the temperature in the room rises to ap
proximately 68°, the contacts 268 and 266 will be
the contacts 2|8Vof the latch open limiting device
Under ythese conditions the gas shutìoilî` valve
13 is deenergized and therefore closed, as »are
the motor |20`and spark transformer 242 which
therefore `are not operating. The variable re
slstor 226 may be in any position such that'the
resistance is fully in or fully out of the circuit, or
somewhere in'lbetween, depending upon the tem
perature of the voutside ambient air as has been
previously indicated.
If, under the above conditions, the heater
cuit is energized, the control transformer
will energize the relay 2 | 0 by way of line 212,
contacts 264 and 260, line 256, contacts 256
248, and line 260. Energization of the coilr 2| 0
closes the'contacts 208 and 2|2,_ as well‘as the
contacts 290. The contacts 290 when closed op
erate to hold the circuit through the relay coil 2 | 0
even though the ñame detector contacts 248 and
256 subsequently open. Operation of the relay
2|0 energizes the motor |20 and the gas shut-off
valve 13 by way of line 206, contacts 208 and
2|2, line 2|4, over-heat limit switch 2|6, the latch
open safety switch 2|8, line 220 and thence
through the gas shut-oil valve coil 13 to the re
turn line-224, and also through the heater |20,
line 288, contacts 284 (these contacts being closed
inasmuch as relay 260 is energized by way of line
212, 214, contacts 266 and 268, line 216,‘relay
separated, thereby deenergizing the coil 218 of
the relay 280. This permits the contacts 284 to
separate, thereby requiring the motor to receive
its current through the reactance 222 and the
variable resistor 226 in shunt therewitln
- The amount of resistance 226 in shunt with
the reactance depends upon the ambient outside
temperature as has been previously described.
If the weather is extremely cold, the resistance
226 Will be su-bstantially completely out of the cir
20 cuit, with the result that the motor |20 operates
almost as fast as it does when the contacts 284
are closed. The heat output, therefore, drops olî
only slightly. If, on the other hand, the outside
air temperature is quite mild, the resistance 226
25 will be annost completely in the circuit with the
result that the resistor 226 and reactance 222 will
divide the current to the motor in such manner
that the motor operates with much lessL current
flow than when the contacts 284 are closed. The ~
30 result is that the motor speed is much lower and
therefore the heat output rate is much lower. In
general, the system should be so balanced that
the heater will normally almost but not quite
maintain the desired room temperature at any
35 given outside air temperature at the low heat out
put rate as set by the temperature bulb 232 for
that particular temperature.
If the room now commences to cool and the
temperature drops below 68°, the contacts 266 and
coil 218, and return lines 262 and 254) and thence
by way of line 286 to the return side of the line 40 268 re-close, thereby closing the contacts 284
which in turn speeds up the motor |20, thereby
224. Also the spark transformer 242 will be en
shifting the heating system to the high heat out
ergized by way of line 224, the primary winding
put level.
240, flame detector contacts 236 and 246 to the
On the other hand, if the temperature in the
return line 224. `Energization of the primary. 45
room continues to rise after the heater has been
of course, energizes the secondary 282 so as to
shifted to the lower heat output level and the
produce sparking at the plug 16, it being assumed
temperature rises above 70° or thereabouts, the
throughout the description that the line 202 is
contacts 264 and 260 are separated, thereby de
connected to an alternating current circuit.. Fur
ther the heaterl coil 2|1 of the latch open safety 50 -energizing the relay coil 2|0, inasmuch as the
flame detector contacts 238 and 256 have already
switch is energized by way of the line 220 and
been separated, with the result that the circuit
line 234, leading to contact 236 of the flame de
to the motor |20, gas shut-off valve 13 and spark
transformer 242 is interrupted by the separa
The end result is that the ignition is turned
tion of relay contacts 208 and 2|2.
on, the blowers are operating, and fuel is being 55
If the temperature now starts falling and drops
supplied through the gas `control valve 12. Inas
below 70°, the contacts 260 and 264 re-close and „
much as the motor is running at full speed, the
the heater is restarted at the low heat level, pro
gas will be supplied at the maximum rate as has
viding enough time has intervened to permit the
been previously described.
- '
If the heater does not start within 45 seconds 60 flame detector to cool sufllciently so that con
tacts 248 and 256 have re-closed. If, however, the
or so, the safety switch 2|8 will be suiilciently
flame detector has not had an opportunity to re
heated by the coil 2|1 so that it opens the cír
cuit to the motor |20, gas shut-off valve 13 and ` close, nothing happens until the flame detector
has had an opportunity to cool. The flame detec
spark transformer 242. Once opened, the switch
tor therefore protects the latch open switch 2|8
2|8 will not re-close until manually re-set.
that it always gives the latch open switch an
If the heater starts immediately in the nor
opportunity to cool before the start of a new
mal manner, the flame detector contacts 236 and
cycle. This is advisable since otherwise it is
246 will be separated as will contacts 248 and
possible that the heater might have been turned
256 in approximately 15 to 30 seconds. Opening
on just long enough to cause the heater 2|1 to
of the contacts 256 and 248 will deenergize the 70 bring
the latch open switch up almost to opening
relay coil 2|0, were it not for the holding con
at which point if someone moved
tacts 290. Since these holding contacts remain
the thermostat to a lower temperature setting,
closed, separation of the contacts 248 and 256
thereby turning on’ the heater, and then moved
in the flame detector has no immediate effect
it back-again to a suiñciently high temperature
excepting to condition the circuit for future oper 75
setting to cause the heater to come on once more,
it would be possible for the heating element Ill
to be reenergized. such that the heat additionally
supplied plus the residual heat remaining in the
device from the last cycle might be enough to
supplying means, connections for supplying fuel
to said heater means, valve means in said con
nections for controlling the rate of fuel ilow to
said heater means in response to the rate of com
bustion air ilow, thermostatic means sensitive to
the heated space temperature for cycling said
functioning in the heater. This is prevented by
heater means between high heat and lower heat
the llame detector contacts 256 and 248 which,
positions, and other thermostatic means operative
under the above recited conditions, would remain
when the heater means is cycled to the lower heat
open between the cycles long enough to permit 10 position for varying the rate of combustion air
the switch 2 I8 to cool nearly to ambient temper
now, the last said thermostatic means being sen
ature before reenergization of the circuit through
sitive to changes in ambient air temperature, and
the heater coil 2| 1.
means operated by the first thermostat when
If at any time the heater becomes too hot, the
said first thermostat is moved to the high heat
over-heat control 2li opens and shuts of! the 15 position to render said second thermostat ineffec
tive to affect the combustion air ilow rate.
While in the above description of a preferred
3. In a heating system, a heat exchanger, ven
embodiment of v the invention certain speciñc
tilating air circulating means for withdrawing air
temperatures and time intervals have been re
from the heated space for passing the air thus
cited. it will be understood that they are used 20 withdrawn over said heat exchanger and for re
merely by way of illustration and not in a limit
turning the air from the heat exchanger to theV
heated space, combustion means for heating
ing sense, and further it will be apparent to
said heat exchanger, means for supplying com
those skilled in the art that substitutions and
modifications may be made while still retaining
bustion air at a variable rate to said combustion
the substance of the invention.
25 means, said combustion air supply means being
connected to receive combustion air directly from
Having thus described my invention, what I
cause this switch to open and latch in the open
position, even though there was no abnormal
the outside atmosphere, thermostatic means sen
claim as new and useful and desire to secure by
. sitive to the temperature of the heated space to
Letters Patent of the United States is:
1. In a heating system, the combination com
cycle said combustion means between high heat
prising a combustion air blower, a Ventilating air 30 and lower heat positions, and other thermostatic
means operative when the combustion means is
blower, a variable speed drive means connected
cycled to the lower heat position for varying the
to drive both said blowers, heater means, duct
rate of supply from the combustion air supplying
means for connecting said combustion air blower
to supply combustion air to said heater means,
means, the last said thermostatic means being
said Ventilating blower being arranged for venti 35 sensitive to changes in ambient air temperature
lating said heater means, connections for supply
and being located within the combustion air sup
ing fuel to said heater means, valve means in said
ply connection.
connections for controlling the rate of fuel flow
to said heater means in response to the rate of
combustion air ñow, thermostatic means sensi 40
tive to the heated space temperature for cycling
The following references are of record in the
said heater means between high heat and lower
ille of this patent:
heat positions, other thermostatic means opera
tive when the heater means is cycled to the lower
heat position for varying the speed of said drive
means. the last said thermostatic means being
sensitive to changes ínrambient air temperature,
and means operated by the ñrst thermostat
when said iirst thermostat is moved to the high
heat position to render said second thermostat
ineffective to aiïect the combustion air flow rate.
2. In a heating system, the combination com
prising means for supplying combustion air at a
variable rate, Iheater means, duct means for con
necting said heater means tosaid combustion air
Scudder __________ __ May 4,
McKee __________ _- Oct. 11,
Harrington ...... __ Oct. 24,
Bulkeley ________ __ Mar. 6,
Lamb ____________ __. Apr. 28,
Hartig __________ __ Aug. 13,
Keller ____________ __ Dec. 10,
Grant _________ _,--- Dec. 24,
Holthouse ______ __ June 16,
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