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Патент USA US2129526

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Sept. 6, 1938.
H. R. CRAGO
2,129,526
CONTROL SYSTEM AND APPARATUS FOR HEATING
Fil'ed Feb. 16, 1935
4 Sheets-Sheet 1
LI
Fig. I. _
Inventor“ 1
by
Harry R. Crago,
815
His ?ber-‘neg.
Sept. 6, 1938.
. H. R. CRAGO
2,129,526
CONTROL SYSTEM AND APPARATUS FOR HEATING
Filed Feb. 16, 1935
4 Sheets-Sheet 2
Inventor‘?
Harry R. Crago,
b9 NW7 5.8M
His Att/OT‘T‘IGH.
Sept. 6, 1938.
H. R. CRAGO
2,129,526
CONTROL SYSTEM AND APPARATUS FOR HEATING
Filed Feb. 16, 1935
4 Sheets-Sheet 3
.lnventor'i
Harry R.Cr~ o,_
by WW7
219M212“
His Attorney .
Sept. 6, 1938)
2,1_ 29,526
H. R. CRAGO
CONTROL SYSTEM AND APPARATUS FOR HEATING
4 Sheets-sheet 4
‘ Filed Feb. 16, 1935
Fig.4.
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$458
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Inventor:
Har‘rg R. Cr <20,
b9
His Attorney.
2,129,526
Patented Sept. 6, 1938
UNITED STATES PATENT OFFICE.
2,129,526
CONTROL SYSTEM AND APPARATUS FOR
'
HEATING
Harry B. Crago, Schenectady, N. Y., assignor to
General Electric Company, a corporation of
New York
Application February 16, 1935, Serial No. 6,829
14 Claims. (CL 236-—1)
The present invention relates to control sys
tems and apparatus adapted for controlling the
operation of a plurality of automatic combustion
heaters supplying a variable heating load, par
; ticularly a plurality of electrically operated on
?red boiler furnaces for supplying steam to a
variable pressure load although certain features
of the invention are not necessarily limited
thereto.
-
-
One of the principal objects is to control auto
matically the number of heaters in operation in
accordance with predetermined variations of the
heating load. In this way the number of elec
trically operated oil ?red boiler furnaces in op
15 eration may be varied in accordance with the
variations in pressure of the steam load.
10
Another object is to obtain selectively differ
' ent starting sequences for the plurality of heaters
and thereby distribute the operating duty more
which Fig. 1 schematically shows a preferred form
of the improved control systems and apparatus
of the present invention applied to a plurality of
automatic combustion heaters supplying heat to
a common heating load; Fig. 2 is a circuit dia
gram showing more clearly the details of the
boiler furnace portion of the improvedvheater.
control system and apparatus of Fig. 1; Fig. 3
is a circuit diagram showing the details of the
forced draft portion of the improved heater con 10
trol system and apparatus of Fig. 1, the diagrams
of Figs. 2 and 3 being complementary; and Fig. 4
is a circuit diagram showing the details of the in
dicating signal light control arrangement shown
schematically in Fig. 1.
Referring to Fig. 1, several groups of boiler fur
naces G1 to G3 are shown in the preferred form
of the invention connected to supply steam to
' conditions a predetermined time delay in the
the steam main I0 although the present invention
is not limited to group operation. The boiler
furnaces F1 to F5 comprising group G1 as well as
the boiler furnaces comprising the other groups
are shown interconnected by improved grouping
means, more fully described and claimed in the
.25 starting of successive heaters into operation even
though excessive increase of the heating load
should occur. This prevents hunting action due
copending application of Clyde C. Colby, Serial
No. 758,276, ?led December 19, 1934, and assigned
to the assignee of my present invention.
to starting and then immediately stopping the
heaters upon temporary load ?uctuations.
A further object is to provide for rapid suc
30
cessive starting of the heaters into operation
without anytime delay under predetermined con
Each of the boiler furnaces F1 to F5 as well as
the other furnaces in Fig. 1 are illustrated as of
20 uniformly among the various units without exces
sive wear and tear falling on any particular
.
heater or groups of heaters.
It‘ is also an object to provide under normal
ditions such as excessively low steam pressures.
Another object is ,to effect the stopping of op
35 eration of any heater only upon a decrease of
the heating load greater than the increase of
the heating load required to effect the starting
of operation of the heater. This also serves to
stabilize the number of heaters maintained _in
4O
operation under quickly ‘varying load conditions.
automatic heater.
Each boiler furnace is pro
vided with suitable automatic electrically oper
ated oil burner mechanism and control. The ar
rangement is such that upon energization of the
control combustion is established automatically 40
A still further object isv to provide for remov
in the boiler furnace and upon deenergization of
ing any boiler furnace from its normal operat
the control the combustion is stopped. One form
of electric oil burner control apparatus suitable
ing sequence and at the same time provide safety
protection for each individual boiler furnace so
4
the automatic electrically controlled oil ?red type 30
described and claimed in the copending applica
tion of Harry S. Woodrui’f, Serial No. 676,651,
?led June 20, 1933, and‘ assigned to the assignee
of my present invention although the present in
vention may be used with any suitable type of
removed as well as for the group of boiler fur
naces remaining in sequential operating condi
tion.
'
Another object is to provide a forced draft for
a plurality of sequentially operated combustion
50 heaters which is varied in accordance with the
number of heaters operating and in addition pro
vide for maintaining the draft substantially uni
form independently of atmospheric conditions.
Further objects will appear from the following
55 description of the accompanying drawings in ‘
for this purpose is disclosed and claimed in the
copending application, Serial No. 735,103, of John
Eaton, ?led July 14,1934, and assigned to the as
signee of my present invention.
Briefly, with the furnace grouping means
shown, each of the furnaces F1 to F5 is connected
to supply steam to the ‘common steam drum l I 50
at the center of the group, which drum is con
nected to the steam main III ‘by the steam feeder
l2 having the manual ‘shut-off yalve I3 therein.
The steam main l0 may be connected to supply
steam to any variable load such, for exampleyas 55
2
2,129,626
the steam heating radiators of a large building
or of several smaller buildings. In suchheating
service, the condensate may be returned from all
of the radiators through the return water line l5
which is connected through the pipe IS with the
of the dial arm 42 through the corresponding
offset positions P6 to P10.
A manually operable sequencing switch S1 is
provided for selectively varying the operating
sequence in which the groups of boiler fur
naces G1 to Gs are started into operation under
of boiler furnaces with the manual cut-off valve . the control of the dial switch 42.
I! located in pipe l6. Return water line 15 may
The reversible motor 4| drives the dial arm 42
be similarly connected to the other groups of through suitable speed reducing gearings 45 and
common return water drum I‘! for the group G1
10
furnaces.
the sprocket chain 46.
'
The main flue pipe 20 having the electric
motor driven forced draft fans M21 and M22 as
well as the reversible electric motor operated
draft regulating damper Mm located therein is
15 connected to the common ?ue pipe 25 of the
group G1 of boiler furnaces with the manually
operable draft cutoff gate 26 located in the
common ?ue pipe 25. Each of the other groups
of furnaces G: to Gs is connected to the main
20 ?ue‘pipe 20 in a similar manner.
A master steam pressure responsive control
device 30 is connected to operate in response to
variations in the pressure of the steam main [0
due to variations in the heating load. The
25 control panel 3| contains electrical controlling
apparatus shown in detail in Fig. 2 which is op
erated under the control of the master controller
ll so as to start and stop operation of the vari
ous groups of boiler furnaces G1, G: in accord
ance with the varying demands of ‘the heating
load. The control panel 82 contains the elec
trical control apparatus illustrated diagram
matically in Fig. 3 which is electrically connected
A cam 41 is also driven
through the reduction gearing 45 so as progres
sively to raise or lower the pivoted arm 48 upon
the end of which the contacts 37 and 38 are
carried. In this way the dial arm 42 is operated
to each of the different positions P1 to P10 when 15
the pressure responsive device 30 responds to
different pressure values in the steam main Iii.
Forced draft control
Before operation of any group of the boiler 20
furnaces can be started, it is necessary that
proper draft conditions be established in the
main ?ue 20 by operation of one or the other
of the electric motor-driven forced draft fans 2i
and 22. As shown in Fig. 3 the manually. oper
able selective switch S2 is provided for ‘starting
operation of a selected one of the motor driven
draft fans. The electric driving motors Mai and
M22 of the fans are shown in Fig. 3 as of the
three-phase variable speed type having the 80
several groups of speed regulating resistors R1
to Rs in their secondary circuits.
The forced draft fan motors M21 and M2: are
controlled by the two line switches 5i and 52
with the control apparatus of panel II so as to
operate the forced draft blowers Mn and Mn and having the cooperating relays 53 and 54 to
gether with the timing relay 55 and the speed re
the draft regulator M2: to maintain proper draft
conditions as the number of groups of furnaces sponsive switches 2M and 262 arranged so that
whenever one of the forced draft fan motors
operatingis varied in accordance with the heat
is operating, upon failure thereof the other
ing load.
The indicating panel 81 contains a number forced draft fan motor is automatically started _
of groups of indicating electric lamps 11 to I:
which correspond in position and in arrange
ment with the various furnaces in the groups G1
to (is. In the manner explained hereinafter,
the center light of each group is illuminated
whenever the corresponding group of boiler
furnaces is started into operation and the outer
lights of each group are illuminated as the cor
responding furnace in the group starts opera
tion.
Furnace group control
The multiple furnace control apparatus shown
in the diagram of Fig. 2 is controlled by the
master steam pressure responsive device 30.
This device is shown as of the type having a
pressure responsive diaphragm inside of the cus
ing 35 which raises and lowers the movable
switch contact arm 36 upon an increase and
decrease of the steam pressure in the steam
main III. A pair‘ of spaced-apart contacts 31,
I0 cooperate with contact arm I. to energize
the
electromagnetically
operated
reversing
switches 39 and M for the reversible electric
motor ll.
‘
The motor ll rotates the dial switch arm 42
in each direction through the series of operat
ing positions P1 to P10 in which a series of elec
tromagnetically operated switches C1 to Co are
into operation. The indicating lights L21, Lu,
and L2: are provided to show the operating con
dition of the forced draft fans, either of the
lamps L21 or L2: being illuminated when the cor
responding forced draft fan 2| or 22 is started
into operation under the control of the selective
switch So. The lamp L2: is illuminated when
ever an automatic changeover has been effected
due to failure of one of the forced draft fans.
Operation
Electric power is supplied from the three-phase
lines L1, La, L: with the neutral line N providing
a suitable lower voltage for the control and in
dicating lamp circuit. To initiate operation of
the electrically operated oil fired multiple boiler
furnace steam plant illustratedin Fig. 1, the
selective switch S1 shown in Fig. 2 is moved
either to the right or the left to establish the
desired sequence of operation of the groups of
boiler furnaces G1 to Gs. The selective switch
S2 shown in Fig. 3 is then thrown either to the
right or to the left to select either one of the
forced draft blowers 2i or 22 for operation.
With selective switch 8: moved to the left, an
energizing circuit for the operating winding of the
line switch SI for the forced draft motor Mn is
established. This circuit extends from the supply
line L: through conductor 60. blade SI of the selec
tive switch S2, the circuit protecting fuse 82, con 70
ductor 03, the movable contact arm N of the tim~
ing switch 55, the blade 65 of selective switch S2
in its left hand position, conductor 66 ‘and thence
through the operating winding of the line switch
70 controlled for starting and stopping operation of
the various groups of boiler furnaces G1 to G.
in sequence. The furnaces are started into op
eration in sequence‘upon movement of the dial
arm 42 through positions P1 to PI and are
75 stopped successively upon the return movement V II and the left hand one of these three phase Tl
2,129,526
conductors 61 to the supply line L1. Line switch
5| immediately closes to energize the motor M21
from supply lines L1, L2, L3. At the same time the
operating winding of relay 53 is energized from
conductor 66 in parallel with the operating wind
ing of line switch 5| and the relay 53 therefore
closes;
‘
‘
In order to insure rapid acceleration of vthe
motor M21, provision is made for cutting out the
10 section R1 of the speed controlling resistor until
the motor M21 has accelerated to running speed.
This is accomplished in the following manner.
When conductor 66 is energized to close the line
switch 5|, a circuit extending through conductor
15 'IDand the contact of the speed responsive switch
6| in its right hand position as shown in the draw
ings, conductor ‘II and the operating winding of
the electromagnetic accelerating switch ‘I2 to
supply line L1 is established.
20
‘
‘ Upon closure of accelerating switch ‘I2, an ener
gizing circuit for the operating winding of the
electromagnetic switch ‘I3 for short circuiting the
resistors R1, R4 is established. This circuit may
be traced from the supply line L2 through con
25 ductors 80, 8|, 82, the middle contact of relay 53,
conductor 84, the contacts of switch 12, conductors
85 and 86, the winding of switch 13, conductor 61,
and thence through conductor 88 to the neutral
supply line. The resulting closure of switch 13
30 short circuits the resistors R1 and thus enables the
motor M21 to accelerate quickly to running speed.
Draft fan changeover operation
When selective switch-S2 is moved to the left to
35 energize the line switch 5| for the forced draft
fan motor M21 through a circuit including the
conductor 63, at the same time the operating
electromagnet 90 of the timing device 55 is ener
gized, the circuit extending from conductor 63
40 through the winding of the electromagnet 90 and
conductors 9| and 80. Likewise, the energizing
Winding of the induction disk timing motor 92 is
energized from the midtap of electromagnet 90,
conductor93, movable contact arm 94 and con
45 ductor 63, the motor energizing winding being
connected in parallel with a portion of the wind
ing of the operating electromagnet 20. Energiza
tion of the operating electromagnet 90 attracts
the armature 95 and thereby sets up a force to
50 engage the gears 98 and also tends to move the
contact arms 64 and 94 from the positions in which
they are shown in the drawings. This latter, how
ever, is prevented by the pivoted latch- 96. How
ever, after the induction disk motor 92 has been
55 energized for the predetermined time interval
sufficient to rotate the trip pin 91 through the
agency of the speed reducing gears 98, latch 96
Will be released and both contacts 64 and 94 will
be operated from their position shown, the con
60 tacts 94 thereupon deenergizing the motor 92.
During the time interval required for operation
of the timing device 55 to move the contact 64
. from the position in which it is shown to its other
65 position, the motor M21 has had an opportunity to
start from rest and accelerate up to running speed
due to the resistor R1 being short circuited. As
soon as motor 2| reaches running speed, the speed
responsive switch 26I which is shown as of the
-70 centrifugal type operates its contact from the
right hand position shown to the left hand posi
tion. The movement of switch 26I from the
right hand position deenergizes the electromag
netic switch ‘I2 and thereby effects deenergization
75 of the switch ‘I3 so as to reinsert the resistor R1 in
3 .
the motor circuit and thereby maintain the motor
at the minimum running speed.
When the speed responsive switch 26| is'moved
to its left hand position, a circuit is established
extending from line L2 and conductor 60 through
blade 6| of selective switch S2, fuse 62 and blade
I00, conductor IOI, switch 26I in its left hand
position, conductor 10, and thence through con-v
ductor 66 and the operating winding of line switch
5|. This circuit maintains the operating winding 10
of the line switch energized preparatory to the
contact 64 of the timing device 55 being moved
from the position in which it is shown after the
predetermined time interval of operation of motor
32 mentioned above. Thus, after this interval, in 15
case the fan motor M21 should stop operation for
any reason so that the speed responsive switch
26| is returned from its left hand position indi
cating normal running speed of the motor, the
line switch 5| will immediately be deenergized.
20
When line switch 5| is deenergized due to stop
ping of the motor M21, it operates to close its
auxiliary contact I02. This immediately estab
lishes an energizing circuit for line switch 52 so as
to immediately start motor M22 into operation. 25
This circuit may be traced from line L3 and con
ductor 60 through blade 6|, fuse 62, conductor 63,
contact 64 of timing device 55 in its right hand
position, blade I03 of the selective switch S2 in its
left hand position, conductor I04, auxiliary con
tact I02 and thence through the operating wind
ing of the line switch 52 to the left hand conductor
61 and line L1.
Upon the energization of the operating winding
of switch 52, the winding of relay 54, is energized
in parallel therewith through the conductor I05.
Thus when motor M22 is initially energized, the
speed responsive switch 262 in its position shown
serves to complete a circuit from conductor I05
through conductor I06 to energize the electro 40
magnetic switch I0'I. Closure of switch |0‘| serves
to energize the resistance controlling switch 13 in.
substantially the same manner as previously
described.
The indicating lamps L21, L22, and L2: are con
nected so that when the selective switch S2 is
moved to the left to initiate operation of the
forced draft blower motor M21, a circuit extend
ing from supply line L1 through conductors 80,
8|, blade IIO, lamp 2| and conductors 81 and 88
is established.
This results in illumination of
the lamp L21 to indicate that the forced draft fan ~
motor M21 is in operation. In case motor M21
stops and line switch 5| and relay 53 are de
energized in the manner described above, the
changeover indicating lamp L23 is illuminated,
the energizing circuit therefor extending through
blade IIO, conductor III, the lower contact of
relay 53, conductor “2, lamp L22 and thence
through conductors 81 and 86 to the neutral sup
ply line. This enables an attendant to inspect
the motor driven draft fan M21 and determine the
cause of the automatic changeover.
Whenever the selectiveswitch S2 is moved to
the right hand position instead of left hand as
previously assumed, the forced draft fan motor
M22 and indicating light L22 are energized in sub
stantially the same way as the motor M21 and
light L21 with the speed responsive switch 262,
contactor |0‘| and‘the timing device 55 function 70
ing in practically the same manner as previously
described. Also upon any failure resulting in
stopping of the motor M22, the speed responsive
switch 262 serves to eifect automatic changeover
to the motor M21 in practically the same way as
4
2,129,526
previously described, at the same time causing
illumination of the changeover indicating light
Lu.
Furnace operation
Before starting operation of the boiler fur
naces, one of the forced draft fan driving motors
M21 or M22 must be in operation and the corre
sponding one of the relays 53, 54 energized in the
manner previously described. Also, a safety con
10 trol circuit must be established from the line L1
through conductors 80, H3, I I4, the dial switch
arm 42 in the off position shown, conductors H5
and H6, blade III of the selective switch S1
in either of its positions, conductor H9 and the
16 upper contact of one of the relays 53 or 54, con
ductor II9, contact I20 of the draft responsive
device DR, contact I2I of the steam pressure re
sponsive safety switch shown in Fig. 1 connected
to the main steam line I0, the manually operable
emergency switch E which must be in the closed
position and thence through the operating wind
ings of electromagnetic switches I30 and HI in
parallel and through conductors I32, I33 and 89
to the neutral supply line.
26 " In this way, it is insured that both the line
contactor I30 and the master control contactor
I3I can be closed only under the following con
so
ditions:
(1) One of the forced draft fans M: and M21
must be in operation,
(2)
value
(3)
main
(4)
The draft must be above a minimum safe
as determined by the draft regulator DR,
The pressure existing within the steam
I0 must be below the maximum safe value,
The manually operable emergency switch
E must be in the closed position,
’
(5) The manually operable sequence selecting
switch S1 must be operated to one of its circuit
40
closing positions,
\
(6) The dial switch arm 42 must be in the off
position as shown in Fig. 2.
-
As soon as the master control contactor I3I is
closed the upper contact thereof shunts the con
tact controlled by the dial switch 42 in the off
45 position. This maintains the continuity of the
safety control circuit traced above when the dial
switch arm 42 is operated from the off position
to start the groups of furnaces into operation.
In this way, undervoltage protection is provided
50 since the contactor I3I will drop out upon volt-v
age failureor reduction of ‘the voltage to an un
safe value and thereby require the return of the
dial switch arm 42 to the of! position before the
safety control circuit can again be completed.
55
Assuming after a shut down of all the furnaces,
there is no pressure in the steam main I0.
Hence, the pressure responsive device 30 will
maintain the contact arm 36 into engagement
with the cooperating contact 31. This estab
60 lishes an energizing circuit for the electromag
netic switch 39 to operate the control motor H
in thedirection to move the down switch arm 42
in a counter-clockwise direction so as to start a
group or groups of the boiler furnaces into opera
tion to supply steam.
I
The circuit for switch 39 may be traced from
the supply line L1 through conductors 90, H3,
I30, the middle contact of the master control
70 switch I3I in its upper position, conductor. I39,
' switch arm 39, contact 31, the contacts of the
electromagnetic limit switch I31, the timing con
I tact I49 of the timingdevice “I, the upper con
tacts of the electromagnetic switch 40, the wind
ing of electromagnetic switch 39 and conductor
I33 to the neutral supply line N. Upon the re
sulting closure of electromagnetic switch 35, the
motor M is energized from the supply lines L1,
L2, L3 through the line switch I30, and the dis
connecting switch I42 in the closed position.
Thereupon motor 4| operates to move the dial
switch arm 42 from the off position in the
counter-clockwise direction.
The electroresponsive timing device MI is
energized at the same time as the winding of the
electromagnetic switch 39, being connected in
parallel therewith through the timing contact
I40. In the preferred form shown the timing
device “I is a self-starting synchronous motor
driving the timing cam I43. After a relatively
short time interval of operation of the timing
cam I43, the timing contact I40 is disengaged
from its lower co-operating contact and operated
into engagement with its upper co-operating
contact by the biasing spring I44, thus maintain
ing the timing device I“ energized.
2.0
In connection with the timing device, it should
be noted that the timing cutout contact I50 is
maintained in the open position shown by means
of the steam pressure responsive device I5I only 25
when the pressure in the steam main I0 is above
‘a predetermined minimum value. Thus, after
normal operating conditions are established, the
operation of the timing contact I40 from its lower
position will deenergize the electromagnetic switch -30
39 and thereby stop operation of motor 4 I. How
ever, the timing device I4I will be maintained
energized and continue to operate timing cam I43
so as to reengage the timing contact I40 with its
lower contact after a predetermined time interval
has elapsed. This will reenergize electromagnetic
switch 39 and restart the operation of motor 4|
to advance the dial switch arm 42. In this way,
under 'normal conditions, the timing device U
will continue to operate the timing contact I40 so 40
as to periodically interpose a time delay in the
advancement of the dial switch arm 42 in the
clockwise direction.
'
However, in starting operation, when the pres
sure in the steam main I0 is below the predeter
45
mined minimum value, the timing cutout contact
I50 is maintained closed. This renders the timing
device I4I entirely ineffective to interpose the
time delay in the operation of the dial switch
arm 42 in the counter-clockwise direction since 50
the electromagnetic switch v39 is maintained ener
gized through contact I50 even though the timing
contact I40 is operated to its upper position.
Thus in starting, the dial switch arm 42 is
rapidly advanced to position P1. Thereupon, the 55
relay C1 is energized, the circuit extending from
L1 through conductors 90, H3, H4, segment I52,
contact P1, conductor I53, the winding of relay
C1, resistor R11, and conductor I33 to the neutral
supply line N. Upon closure of relay C1, the upper
contact thereof establishes a holding circuit for
the relay C1 directly to conductor H4 and in
dependent of the dial switch arm 42.
Upon closure of relay C1, two groups of the elec- trically operated oil fired boiler furnaces are 65
started into operation, the particular groups de
pending upon the position of the selective switch
$1. With the switch S1 in its left hand position,
the furnace groups (1’! and Ga are energized upon 70
closure of the relay C1.
Group control circuits
Fig. 4 illustrates diagrammatically a control
circuit arrangement suitable for the automatic .15
2,129,526
furnaces in each group.
In this arrangement,
5
of the furnaces F1 to F5 in parallel circuit. Each
of the control mechanisms I56 at once starts
motor operated oil burner mechanism I55, a con
operation to run the electric motor driven oil
trol mechanism I56, and a combustion responsive _ burner mechanism I55 so as to establish com
device I51. These may be of any ordinary type bustion in the corresponding furnace F1 to F5.
although the forms shown are intended to repre
As soon as combustion is successfully established
sent diagrammatically apparatus such as dis
in each furnace, the combustion responsive
closed in the copending application, Serial No. switch I51 of that furnace responds to energize
735,103, of John Eaton, ?led July 14, 1934, and the corresponding one of the individual furnace
~ each of the furnaces is provided with an electric
10 assigned to the assignee of, my present invention.
Each furnace control mechanism includes a
pair of safety switches I58 and I59. While not
shown in detail the safety switch I58 is arranged
under normal conditions to remain in the closed
position as shown but to be operated to the open
position to 'deenergize the burner mechanism I55
upon the occurrence of excessive or dangerous
pressures in the combustion chamber of the oil
furnace.
Such a safety switch arrangement is
20 disclosed and claimed in Patent 1,987,447 of W. O.
Lum, granted January 8, 1935, and assigned to the
assignee of my present invention.
The safety switch I59 also under normal con-‘
indicating lights A1 to A5. These individual fur
nace indicating lights are arranged around the
central furnace group indicating lights As so as
1,0
to correspond to the physical arrangement of
the furnaces’ F1 to F5 as shown in Fig. 1. Thus
as each of the lights A1 to A5 is lighted, the 15
operator knows that the corresponding furnace
has established combustion and is in proper op
eration. In case one of the lights A1 t0_As fails
to light, the operator at once knows that the
corresponding furnace has failed to establish 20
combustion. This facilitates an immediate in
spection of any defective furnace to determine
the cause of failure and the necessity of repairs
ditions remains in the closed position as shown [or adjustments.
The group of furnaces Gs is connected and ar
but is operated to the open position to deenergize
the burner mechanism I55 upon the occurrence of ranged to be energized upon closure of relay C1
excessive steam pressure in the boiler furnace. in substantially the same way as the group of
Any ordinary form of safety pressure switch may furnaces G1 indicated in Fig. 4.
be employed.
Group sequemrinp
.
As shown in Figs. 1 and 4, each group of boiler
If
the
heating
load
conditions
are
such
that
furnaces is provided with a draft damper safety
switch I66. This switch is normally maintained voperation of the two groups of furnaces G1 andv
Ga will supply su?icient steam to the steam main
in the closed position as shown .as long as the
damper remains in the fully open position. When II! to balance the demand, thenthe pressure
the draftdamper in the common ?ue pipe 25 for responsive device 35 will operate to disengage the
the group of boiler furnaces is closed, switch I60 contact arm 36 from the contact arm 31. This
is opened. Thus, the draft damper safety switch opens the circuit extending from the contact
prevents operation of any furnace in the group 31 through the limit switch I31 to the timing
except when the common ?ue pipe draft damper device “I. However, as long as the timing con
tact I40 remains in engagement with its upper
40 is opened.
I
Also as shown in Figs. 1 and 4, one of the boiler co-operating contact, the timing device “I will
furnaces in each group is provided with a low continue to operate until the timing cam I43 is
water level safety switch I6I. As long as the rotated to move the timing contact I40 out of
water level in the boiler gr'oup remains at or above engagement with its upper contact. Thereupon
normal value, switch I6I is maintained closed. the timing motor I.4I is deenergized and the
When the water level falls to a dangerously low furnace groups G1 and G8 continue to supply
value, the switch I6I is opened. This either stops the load requirements of steam main III.
In case the load increases, the pressure in the
or. prevents operation of the oil burner mecha
steam main ID will be decreased. As a result,
nisms of all furnaces in the group.
the steam pressure-responsive switch contact 36
Thus, with the group control circuit arrange
ment shown in Fig. 4, when relay C1 is closed upon is reengaged with contact 31. Thereupon the
operation of the dial switch arm 42 to position P1, timing motor MI and the control motor H are
the group of boiler furnaces G1 is started into again energized in the manner previously de
operation provided all of the safety switches I58, scribed. The control motor 4I immediately
25'
30
35
45
I59, I60 and I6] associated therewith are in the starts to advance the dial switch arm 42 from
position P1 in the counter-clockwise direction,
closed position indicating normal operating con
ditions. To energize the furnace group G1, the When the dial switch arm 42 reaches the posi
conductor I65 is connected through switch blade tion P2, relay C2 is energized in substantially
I66 of the selective switch S1 in its left-hand the same way as previously described in connec
position, the middle contact of relay C1 and the tion with relay C1. Thereupon, the timing de 60
upper contacts of line switch I30 to the supply vice I4I disengages contact I40 from its lower
line L1. The conductor I6'I is connected directly co-operating contact and thus temporarily stops
' further advance of the dial switch arm 42 in the
to the neutral supply line N.
counter-clockwise direction by deenergizing the
When, as shown in Fig. 4, the group of fur
switch 39 and the control motor 4!. The tim 65
' naces G1 is started into operation, an energizing
circuit is established through conductors I65 and ing cam I43 is formed so as to permit the con
'I6'I for the group signal light As. This light is tact I40 to remain in engagement with its lower
located in the center of the indicating group I1 co~operating contact only ‘for the‘. time interval
as shown in Fig. 1. Thus, the lighting of the required for operation of the dial switch arm 42 ~
from one position to the next adjacent position. 70
group indicating light A6 indicates to the opera~
tor that the corresponding group of oil furnaces Thus, after a predetermined time delay, the tim
G1 has been called into operation. At the same ing device “I reengages the timing contact I40
time a circuit is established from conductor I65 ‘with its lower co-operating contact to reenergize
the control motor 4I and advance the dial switch
through the safety switches I60 and I6I to en
ergize the electric control mechanism I56 of each arm 42 to the next adjacent position.
2,129,520
6
In this way, relays Ca, C4, C5 are succemively
energized when the dial switch arm 42 is ad~
vanced after successive time delay periods to
positions P3, P4, P5, provided the pressure in the
steam main I 0 continues to remain below the
value required for the pressure~responsive de
vice 35 to disengage pressure switch 36 from
contact 31. The provision of the time delay
after advancement of the dial switch arm be
10 tween adjacent positions reduces hunting action
as it enables each group of furnaces to start
15
20
26
30
40
dial switch arm 42 in the clockwise direction.
In case the dial switch arm 42 has been oper
ated in the counter-clockwise direction to posi
tion P5 to energize the relay C5, this relay will
remain energized until dial switch arm 42 is
returned in the clockwise direction to position
Pa.
1c deenerglzation of relay C5 is accom 10
plished by short circuiting the relay windings.
into operation and contribute to the supply of The resistor R15 serves to limit the current where
steam to the steam main in for a predetermined the relay winding is short circuited. Similarly,
time interval before the next group of oil fur~ as positions P7, Pa, P9, and P10 are reached by
the clockwise movement of the dial switch arm 16
naces is started.
The successive energizatlon of relays C1, Ca, t2. the corresponding relays C4, Ca, Ca, and C1
C1, C4, and C5 serves to bring successively all will be successively deenergized by short circuit
groups of the oil furnaces into operation. The ing the operating winding of the relay.
particular sequence of starting the groups of
Referring speci?cally to relay C1, this relay
furnaces into operation is determined by the was energized when the dial switch arm 42 was
position of the selective switch S1. With the voperated in a counter-clockwise direction to posi¢
selective switch S1 in its left hand position, relay tion P1, the energizing circuit extending from con~
01 controls the furnace groups G1 and Gs; relay ductor H4 through the segment I52, dial switch
C: controls furnace group G3; relay Ca controls arm 42, contact P1 and conductor I53 and thence
furnace group G5; relay C4 controls furnace through the winding of relay C1 and resistor R11
groups G4 and Go; and relay C5 controls furnace to the conductor I 33. When relay C1 closes, the
groups G: and G1. With the selective switch S1 upper contact thereof establishes a holding cir
in its right hand position, relay C1 controls fur
cuit directly from conductor H4 through the re~
lay winding and resistor R11 to conductor I33.
nace groups G: and G1; relay C2 controls fur
nace group G4; relay Ca controls furnace group Upon the movement of the dial switch arm 42
(in; relay C4 controls furnace groups G: and G5;
in the clockwise direction to position Pin, the
and relay Ca controls furnace groups G1 and Ga. winding of relay C11 is short‘ circuited through
It is important to note that as the dial switch a circuit extending from the conductor H4, the
arm 42 is advanced through the series of posi
segment I52, contact Pm, conductor H! to the
tions P1 to P: the cam 41 operates to lower the midpoint between the relay winding and the re
arm 48 in steps corresponding to the positions sistor R11. When relay' C1 opens due to the short
of the dial switch arm 42, thereby decreasing the circuiting of the operating winding thereof, the
value of the steam pressure in main ID at which upper contact of the relay interrupts the holding
the pressure contact arm ‘38 is operated out of circuit through which the relay has previously
engagement with the contact 31. As a result, been maintained energized. The short circuiting
the pressure in the steam main I0 is changed of the other relay windings is accomplished in
from a maximum operating value to a minimum substantially the same way.
With the relay energizing and short circuiting
operating value. For ordinary heating service
these values may be assumed to be eight pound arrangement Just described, the dial switch arm
steam pressure for the minimum value and eleven 42 is operated through one series of positions to
pound steam pressure for the maximum value energize the relays and through an entirely dif
although other values may be employed as de— ferent series of positions to deenergize the relays.
This arrangement prevents temporary increases
scribed. With the 8 to 11 pound normal oper
ating range of steam pressures for device II, the in the pressure in the steam main ID from causing
timing cutout pressure switch Iii may be set groups of the oil furnaces to be shut down as it
to close its contact at the subnormal pressure requires a considerable interval of time for the
of seven pounds and the excess pressure switch dial switch arm 42 to be operated by the control
III may be set to open its contact at twelve motor 4| from the position at which any par
pounds.
.,
The safety steam pressure switches I" for the
individual boiler furnaces may be set to open
at fourteen poinds. ‘Then the pop valves ordi—
narily provided under safety rules on each in
dividual boiler furnace may be set to open at
60
ductor I33 to the neutral supply line. The re
sulting closure of switch 40 energizes motor 4| for
operation in the direction required to rotate the
fifteen pounds.
In case the heating load on the steam main
l0 decreases, the pressure in the steam main will
rise due to the fact that the number of furnaces
then in operation will supply more steam than
is required to balance the load demand. As soon
as the steam pressure rises sufficiently for the
pressure responsive device 35 to operate the
pressure contact 36 into engagement with the
upper co-operating contacts )8, a circuit is es
tabllshed from supply line L1 through conduc
tors 80, “3, I35, upper contacts of switch It“,
conductor I36, switch contact 36 and 38, limit
switch I10 in the closed position, conductor I'll,
the upper contact of switch 39, the operating
75 winding of switch 40 and thence through con
ticular group of furnaces is started into opera
tion to the different position at which the par
ticular group is shut down. If during this inter
val the steam pressure returns to its initial value,
the movement of the dial switch arm 42 in the
counter-clockwise direction is stopped so that the
deenergizing position for the particular group of
furnaces concerned will not be reached.
Draft regulation
As the number of groups of furnaces supplying
steam to the steam main Ill is varied automati
cally to meet the load demands, the volume of
the products of combustion from the furnaces
supplied to the main flue pipe 20 is varied corre
spondingly. Hence, to maintain proper operating
conditions, it is desirable that the forced draft be 70
controlled substantially in accordance with the
number of furnaces operating and that the draft
never be permitted to fall below ‘a predetermined
minimum value.
As shown in Fig. 1, the draft regulator DR is
7
2,129,626
connected by the main pipe I15 and the four
branch pipes I16 so as to be responsive to draft
conditions at a plurality of symmetrically lo
cated points in the ?ue piping system for the
furnaces.
This provides an indication of the
average draft condition for all the furnaces.
When this average draft condition falls below
The two time delay auxiliary contacts I14 are pro
vided in order to prevent immediate closure of
resistance controlling switch 15 in case selective
switch S2 is thrown quickly from one position to
the other with the draft fan operating at maxi
mum speed. The delayed closure of switch 15 in
the minimum operating valve, the draft regulat
ing device DR. operates to open the contact I20.
10 With contacts I20 open it is impossible to com
plete the safety circuit through which the con
trol contactor I3I and the line switch I30 for
the furnace groups are energized.
In the arrangement shown in the drawings, the
15 low speed operation of either forced draft fan
is sufficient to maintain the draft above the mini
mum operating value as long as no more than
two groups of furnaces are operating. Thus when
the relay C1 is closed to start operation of fur
20 nace groups G1 and G8 or G2 and G1 depending
upon the position of the selective switch S1,'the
forced draft fan continues in operation at the
minimum speed.
However, when relay C2 is energized to start
operation of an additional group of furnaces,
the draft fan speed control relay C12 is energized.
This relay in turn energizes the electromagnetic
switch 13 to short circuit speed regulating re
sistors R1, R4 and thereby increase the speed of
30 the forced draft fan. Relay C12 is energized
through a circuit extending from the neutral
supply line, conductor 81, the winding of relay
C12, conductor I11, the lower contact of relay C2
in the closed position to supply line L2. The re
sistor controlling contactor 13 is energized by a
circuit extending from the neutral supply line,
conductor 81, the winding of contactor 13, con
ductor 88, the contacts of relay C12, conductor
88, the middle contact of one of the electro
magnetic switches 53 or 54, and thence through
conductors 82, 88 and 80 to supply line L1.
The increased draft in the main flue pipe 20
due to the increased speed of the draft motor
is then sufficient to take care not only of the
group of furnaces added by closure of relay C2
but also the additional group of furnaces added
by closure of relay Ca. However, when relay C4
is closed to start two additional groups of furnaces
into operation, the relay C14 is energized. Relay
C14 in turn energizes the speed resistor controlling
switch 14 so as to short circuit the resistors R2
and R5 and thereby further increase the speed of '
sures that neither draft fan motor can be started
with all the secondary resistance cut out.
As the relays, C5, C4. C2, arev energized or de
energized to start and stop operation of the 10
groups of boiler furnaces controlled thereby, it
will be seen that the speed of the forced draft ‘fan
is varied substantially in accordance with the
number of heaters operating.
This serves to
maintain the draft above'the minimum operating 15
condition at all times.
.
In order further to control draft conditions,
the reversible motor M23 is provided for operating
the draft gate I18 to maintain the draft between
de?nite operating limits. The reversible motor 20
M22 is controlled by the draft circulating device
DR. Whenever the draft increases to the maxi
mum operating value, the switch arm I80 is moved _
into engagement with the contacts I8I so as to
operate the reversible motor M23 in the direction
required to close the‘gate valve I18. The circuit
controlled by switch I80 extends from the supply
line L1 through conductors 80, I I3, I35, the lower
contact of switch I3I in its upper position, con
tacts I8I and thence through the operating wind
ing of the electromagnetic switch I82 and con~
ductor 81 to the neutral supply line. Closure of
said switch I82 energizes the motor M22 through
the field winding I83 to effect operation thereof
in the direction tending to close the gate valve
As the' valve ‘closes the draft is restricted
' I18.
and the draft regulator at once responds to dis
engage the contact I80 from the contact I8I and
thereby stop operation of the motor M23.
Whenever the draft decreases to the minimum
operating value, the contact arm I80 is operated
into engagement with the contact I84 to energize
the electromagnetic switch I85. Closure of
switch I85 energizes the motor M23 through the
?eld winding I86 to effect operation of the motor
in the direction tending to open the gate valve I18.
Thus in addition to the variation of the speed of
the forced draft fan in accordance with the num
ber of furnaces operating, the draft is further
controlled by the gate valve I18 at each operating 00
speed of the forced draft motor so as always to
maintain the draft within the proper operating
the forced 1draft fan which is operating. The
draft due to the increased fan speed is then suffi
cient to take care of the two additional groups of
furnaces controlled by relay C4. Likewise, when
limits.
What I claim as new and desire to secure-by
55
Letters Patent of the United States is:
l. The combination of a plurality of boiler
relay C5 is closed to start the remaining two groups , furnaces connected to supply steam to a common
of furnaces into operation, relay C15 and electro
header and each boiler furnace having an elec
magnetic switch 15 are energized to effect the trically operated oil burner mechanism for
short circuiting of the resistors R2, R6 and thereby establishing combustion to generate steam there 60
increase the speed of the draft fan to the maxi
in, means operable responsively to predetermined
mum value. As the energizing circuits for re
variation of the steam pressure in said header,
lays C14 and C15 are substantially the same as for
sequencing switch mechanism including a re
relay C12 and as the energizing ‘circuit for re
versible motor operated sequencing switch con
sistance controlling switches 14 is substantially trolled by said pressure responsive means, a series
the same as for switch 13, these circuits will be
of separately operable electromagnetic switches
apparent from the drawings without tracing in de~ controlled by said sequencing switch, and a multi
tail.
'
The energizing circuit for the resistance con
70 trolling switch 15 extends through the contacts
of relay C15, conductor I13, and either one of the
'two time delay auxiliary contacts I14 with which
the electromagnetic switches 53 and 54 are pro
vided and thence through the operating winding
75 of electromagnetic switch 15 to conductor 18.
ple contact reversing switch interconnected with
said electromagnetic switches for controlling the
energization of said oil burner mechanisms to 70
start and stop operation thereof in reversible
sequences to regulate the steam pressure.
2. In combination, a plurality of automatic
combustion heaters connected to a common heat
ing load,‘ control means responsive to predeter
75
8
2,129,526‘
mined variations in said heating load and hav
ing load, means responsive to predetermined var
ing a sequencing device controlled thereby for' iations in said heating load and having a mov
starting and stopping operation of said heaters able control member operable through a series
in a predetermined sequence and a timing device
of control positions, and control means operable
periodically starting and stopping operation of upon movement of said member in one direction
said sequencing device, and automatic means for to each control position for energizing a corre
rendering said timing device ineffective in the sponding heater and operable upon movement
sequential starting of said heaters upon a pre~ of said member in the reverse direction from
determined abnormal variation in said load.
predetermined control positions past adjacent
10
3. In combination, a plurality of devices for control positions for deenergizing the heaters 10
supplying a common load, timed sequencing con
trol means responsive to predetermined varia
tions in said load for starting and stopping op
eration of said devices in a predetermined timed
15 sequence, a separate timing means for interpos
ing an additional time delay in the sequential
starting of said devices, and means for render
ing said separate time delay means ineffective
upon a predetermined abnormal variation in said
20 load.
4. In combination, a plurality of boiler fur
naces connected to supply steam to a common
steam header and each having an automatic
burner mechanism for establishing combustion
to generate steam therein, means responsive to
predetermined'variations of the steam pressure
in said header, timed sequencing means con
trolled by said pressure responsive means for
starting and stopping operation of said auto
matic burner mechanism in a predetermined
timed sequence, a separate timing means for in
terposing an additional time delay in the se
quential starting of said automatic burner mech
anism, and pressure responsive means operable
when the steampressure in said header is below
a predetermined value for renderingv said sep
arate timing means inoperative.
5. In combination, a plurality of electrically
corresponding to said predetermined positions.
9. The combination of a plurality of automati
cally operable oil tired boiler furnaces connected
to a common steam header and each having a sep
arately operable electromagnetic switch for auto 15
matically starting and stopping operation of the
corresponding furnace, control switch mechanism
operable responsively to predetermined variations
of pressure in said steam header and having a
member movable through a series of circuit con 20
trolling positions for successively energizing said
electromagnetic switches to start operation of said
furnaces in a predetermined sequence, and means
whereby movement of said movable member in
the reverse direction from predetermined circuit 25
controlling positions beyond the next adjacent
position is required to deenergize the electromag
netic switch corresponding to said predetermined
positions.
‘
10. In combination, a plurality of separately op
erable electromagnetic switches, a dial switch
having a contact arm movable in one direction
over one series of stationary contacts for ener
gizing said electromagnetic switches in a prede
termined sequence and movable in the opposite
direction over another series of contacts in offset
relation with said one series of contacts for de
energizing said electromagnetic switches in the
controlled automatic combustion heaters con
nected to a common heating load, switch :mecha
nism having an off position and a plurality of
reverse sequence at a different position of said
movable contact arm.’
circuit closing positions for selectively connect
ing said heaters for operation in diiferent se
quences, automatic means responsive to prede
termined variations in said heating load, and
electrically operated switching means controlled
by said automatic means and electrically inter
sponsive devices, each having current limiting
11. In combination a plurality of electro-re
means in the energizing circuit thereof, a master
switch having a series of circuit making positions
for energizing said electroresponsive devices in a
predetermined sequence, switching means oper
ated by each device for maintaining the device en
locked with said selective switch mechanism to ergized independently of said master switch
be rendered e?ective upon operation of said se
mechanism, said master switch mechanism hav
60 lective switch mechanism from the oiT position - ing a second series of circuit making contacts for
to one of said circuit closing positions for start
short circuiting said electroresponsive devices in
ing and stopping operation of said heaters in the opposite sequence.
the sequence determined by said selective switch
12. The combination of ‘a plurality of automati
ing means.
‘
55
6. In combination, a plurality of automatic
combustion heaters connected to a common heat
ing load and a load responsive control device
having means for starting said heaters in oper
ation sequentially as the load increases through
a predetermined series of values and having
means for stopping operation of the heaters se
quentially as the load decreases through a lower
predetermined series of values.
7. The combination of a plurality of electrical
65 ly controlled combustion heaters connected to a common heating load, a, movable switch mem
ber having one series of circuit controlling con—
tacts for energizing said heaters in, a prede
termined sequence and a separate series of co
70 operating circuit controlling contacts for de
energizing said heaters in reverse sequence, and
means responsive to variations in said heating
load for operating said member.
8. In combination, a plurality of automatic
75 combustion heaters connected to a common heat
, cally ?red boiler furnace units for supplying steam
to a common header and each having a separably 55
operable valve for disconnecting the unit from
said common steam header, automatic means re
sponsive to predetermined variations in the steam
pressure of said header for starting and stopping
operation of said units in sequence, separate 60
means responsive to the steam pressure of each
boiler furnace unit with the corresponding dis
connecting valve closed for automatically stop
ping operation thereof when said pressure reaches
an excessive value, and means responsive to pres
sure in said steam header for automatically stop
ping operation of all of the units when the steam
pressure reaches a predetermined lower value.
65
13. In a heating system, the combination of a
plurality of automatically operable electrically 70
controlled oil ?red boiler furnace units for sup
plying steam to a common header and each hav
ing a separately operable valve for disconnecting
the unit from said common steam header, auto
matic means responsive to variations of the steam
75,
9
2,129,526
pressure of said header between predetermined
limits for starting and stopping operation of said
unit in sequence, safety means responsive to steam
pressure of said main above said upper limit for
automatically stopping operation of all of said
units, and separately operable means responsive
to generation of a still higher value of steam pres
sure in each of said units when the corresponding
10
disconnecting valve is closed for ‘automatically
stopping operation of said unit independently of
the control of said safety steam pressure respon
sive means.
I
14. In a heating system, the combination of a
heating load, a common ?ue for said combustion
units havinga variable speed electric motor driven
fan for inducing a draft therein, control means
for initiating operation of said fan at low speed,
automatic means responsive to the variations in
said heating load and rendered e?ective upon op
eration of said control means for starting and
stopping operation of said combustion units in a
predetermined sequence and means under the
control of said automatic means for increasing 10
and decreasing the operating speed of said fan _
- upon the starting and stopping respectively of
predetermined units in the sequence.
plurality of automatic ignition combustion units
'15
operable in sequence for supplying a variable
HARRY R. CRAGO.
CERTIFICATE OF CORRECTION.
Patent No . 2,129, 526.
‘September 6,‘ 1958.
HARRY a. CRAGO.
It is herebyr certified‘ that error appears in the printed specification
"of the above numbered patent requiring correction as follows: Page 5, first _
column, line 211,, for the reference character "L2" read L1; page 6, second
column, line 52, for "C11" read C1; page 7, first column, line 8, for the
word "valve"_ read value: and that the said Letters Patent should be read
with this correction therein that the same may conform to the record of
the case‘ in the Patent Office.
” Signed and sealed this 22nd day 61" November, A. D. 1958.
Henry Van Areclale‘v
(Seal)
Acting Commissioner of Patents.
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