Specifications
Page 19
TYPICAL BURNER AND ELEC
TRODE ASSEMBLY
BURNER
AIR SLOTS
ORIFICE
OPENING
ELECTRODE/
FLAME SENSOR
ASSEMBLY
SCREWS
FIGURE 19
D-Primary High Temperature Limit S10
S10 is the primary high temperature limit. It is located in the
heating compartment and is mounted to the lower portion of
the panel dividing the heating compartment from the blower
compartment.
Primary limit S10 is wired in series with the ignition control. Its
N.C. contacts open to de-energize the ignition control when
excessive temperature is reached in the blower compartment.
The limit is a SPDT auto-reset switch. The limit is factory pre
set to open its N.C. terminals at 180F +6F on a temperature
rise and automatically reset at 140F +7F on a temperature
fall. The ignition circuit is immediately de-energized when ter
minals 1-3 open and relay K20 is energized when terminals
1-2 close. This is a primary safety shut-down function of the
unit.
E-Secondary High Temperature Limit S21
S21 is the secondary high temperature limit. It is also located
in the heating compartment and is mounted to the upper por
tion of the panel dividing the heating compartment from the
blower compartment.
S21 is also wired in series with the ignition control. It functions
in the same manner as S10 but is factory set to trip at 150F
+6F on a temperature rise and automatically reset at 110F
+7F on a temperature fall. This is a secondary safety shut-
down function of the unit.
F-Flame Rollout Switch S47
Flame rollout switch S47 is a high temperature limit located
just above the burner air intake opening in the burner enclo
sure. The SPST N.C. limit is connected in series with ignition
control A3. When S47 senses flame rollout (indicating a
blockage in the combustion air passages), S47 trips, the igni
tion control immediately stops ignition and closes the gas
valve. The switch is factory set to trip at 180F and cannot be
adjusted. The limit is a manual reset switch.
G-Combustion Air Prove Switch S18
The combustion air prove switch (S18) is a SPST N.O. centrif
ugal switch inside the combustion air motor. It is used to mon
itor combustion air blower operation. The switch is wired in
series with ignition control A3. On startup, the switch closes
when the combustion air motor reaches between 1850 and
2500 RPM to allow power to the ignition control (proves, by
closing, that the combustion air blower is operating before al
lowing the ignition control to energize). At the end of a heating
demand (when combustion air motor is de-energized), S18
opens when the combustion air motor slows 50 to 450 RPM
below the make." The combustion air prove switch is factory
set and is not adjustable.
H-Combustion Air Blower B6
The combustion air blower provides fresh air to the burner
while clearing the combustion chamber of exhaust gases.
The blower begins operating immediately upon receiving a
thermostat demand and is de-energized immediately when
thermostat demand is satisfied.
All combustion air blower motors are sealed and cannot be
oiled. The blower cannot be adjusted but can be disas
sembled for cleaning.
The combustion air blower uses a singlephase PSC motor
which requires a run capacitor (C3). All motors operate at
3200RPM. All have automatic reset overload protection.
Blowers are supplied by various manufacturers. Combustion
Air Blower Ratings may vary by manufacturer. Specific blower
electrical ratings can be found on the unit rating plate. Both
GCS24-1353 and -1603 use 4.81 x 1.25 blower wheel and re
quires T3 when used on 460v or 575v units.
I-Combustion Air Motor Capacitor C3
The combustion air blower in all GCS24 units uses a
208/230V singlephase PSC ballbearing motor which re
quires a run capacitor. Capacitor C3 is connected to combus
tion air blower B6 and is a 3 MFD-370VAC capacitor.
J-Gas Valve GV1
GV1 is a gas valve used in GCS24 series units. All units are
equipped with gas valve GV1.
Gas valve GV1 is a twostage redundant valve. Units may be
equipped with valves manufactured by either Honeywell or
White-Rodgers. First stage is quick opening (on and off in
less than 3 seconds). Second stage is slow opening (on in 1
minute, off in 1-1/2 minute) On a call for first stage heat, the
valve is energized by the ignition control simultaneously with
the spark electrode. On a call for second stage heat, the sec
ond stage operator is energized after time delay DL3 closes.
When demand is satisfied, second stage must be closed
(1-1/2 minutes to close completely) before 1st stage can
close. A manual shut-off knob is provided on the valve for
shut-off. Manual shutoff knob immediately closes both