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II – UNIT COMPONENTS
G20RE unit components are shown in figure 1. The
blower controls can be accessed by removing the up-
per access panel. Gas valve and burners can be ac-
cessed by removing the lower access panel.
A – Control Box Components
The G20RE control box is shown in figure 2. It is located
behind the lower access panel between the draft hood
and the gas valve. The control box can be accessed by
loosening the top screw and removing the bottom
screw. The control box cover can then be rotated from
the control box. The control box houses the (T1) Trans-
former and serves as a make-up box for low voltage
field wiring. It also contains a grounding lug for the
unit.
G20RE CONTROL BOX - FRONT VIEW
FIGURE 2
CONTROL TRANSFORMER
(T1)
GROUNDING SCREW
1 – Control Transformer (T1)
All G20RE series units use a single line voltage
(120VAC) to 24VAC transformer. It is located inside the
control box providing power to the low voltage section
of the unit.
B – BCC2-2 Blower Control (A15)
All G20RE units utilize a BCC2-2 blower control as illus-
trated in figure 3. It is located behind the upper access
panel on the BCC2-2 blower control panel. The BCC2-2
is a printed circuit board which controls the blower and
monitors primary limit and gas valve operation. The
control has a non–adjustable, factory preset “on” fan
timing. Fan “off” timings are adjustable. The board is
divided into two sections, 120VAC and 24VAC.
“CAB” and “XFMR ” send 120VAC to the damper mo-
tor and transformer, respectively. Active cooling and
heating blower speed terminals and three dummy “D”
terminals are located on the 120VAC side of the
BCC2-2. The “CF” terminal is used for wiring in the op-
tional continuous fan kit. Also located on this side of
the control are neutral terminals and a terminal for ac-
cessories such as an electronic air cleaner.
24VAC from transformer T1 is supplied to terminal
“24V” on the 24VAC side of the BCC2-2. Thermostat
connections and safety circuit terminals are also lo-
cated on the 24VAC side of the control. Fan “off” tim-
ings may be adjusted by changing the position of a
jumper across terminal pins.
XFMRN
HSIN
120VAC OUTPUT
COOLING SPEED TAP TERMINAL
120VAC OUTPUT HEATING
SPEED TAP TERMINAL
120VAC COMMON
G20RE BLOWER CONTROL CENTER
INB
N1
CABN
CAB
L1
A
XFMR
D
D
D
H
ACC
120VAC OUTPUT SWITCHED
ACCESSORY TERMINAL
BLOWER TIME ADJUSTMENT
JUMPER
V
LIMIT
W
WR
Y
T
G
210
270
90
150
24V
T
COM
CF
120VAC OUTPUT
CONTINUOUS FAN TERMINAL
INSULATED COVER
THERMOST
A
T
120VAC INPUT LINE VOLTAGE
120VAC OUTPUT TO DAMPER
DOOR
24VAC COMMON TO TRANSFORMER
120VAC OUTPUT TO TRANSFORMER
DUMMY TERMINAL (NO VOLTAGE)
24VAC COMMON
TO THERMOSTAT
24VAC POWER INPUT
24VAC OUTPUT
THROUGH LIMITS TO IGNITION
CONTROL
24VAC INPUT FROM PRIMARY LIMIT
24VAC INPUT FROM IGNITION
CONTROL SENSING CIRCUIT
120VAC COMMON
FIGURE 3
DUMMY TERMINAL (NO VOLTAGE)
CONNECTIONS
