Control Box Components; Control Transformer T1; Compressor Contactor K1; I Unit Components - Lennox KGB Series Unit Information

I-UNIT COMPONENTS
All 2 through 7-1/2 ton (7 through 21 kW) units are built to
order units (BTO). The KGB unit components are shown in
figure 1. All units come standard with removable unit panels.
All L1, L2, and L3 wiring is color coded; L1 is red, L2 is yellow,
and L3 is blue.
A-Control Box Components
KGB control box components are shown in figure 2. The
control box is located in the upper right portion of the com­
pressor compartment.

1-Control Transformer T1

All use a single line voltage to 24VAC transformer
mounted in the control box. Transformer supplies power
to control circuits in the unit. The transformer is rated at
70VA and is protected by a 3.5 amp circuit breaker
(CB8). The 208/230 (Y) voltage transformers use two
208/230V TRANSFORMER
PINK
GRAY
SECONDARY
208 VOLTS
230 VOLTS
PRIMARY
YELLOW
ORANGE
FIGURE 3
2-C. A. I. Transformers T3 (G, J voltage)
All (G) 460 and 575 (J) voltage units use transformer T3
mounted in the control box. The transformers have an output
rating of 0.75A. T3 transformer supplies 230 VAC power to the
combustion air inducer motor (B6).
3-Transformer T4 (J voltage)
All (J) 575 voltage direct drive units use transformer T4
mounted in the control box. T4 is a line voltage to 460V trans­
former to power the indoor blower. It is connected to line volt­
age and is powered at all times.
4-Terminal Strip TB1
All indoor thermostat connections will be to TB1 located in
the control box. Thermostats without "occupied " and "un­
occupied" modes and installed with economizer or motor­
ized outdoor air equipped units, should have a jumper
across terminals "R" and "OC".
primary voltage taps as
shown in figure 3, while
460 (G) and 575 (J)
voltage transformers
use a single primary
voltage tap.
Page 35
5-Fan Capacitor C1 (three phase)
Fan capacitors C1 is used to assist in the start up of con­
denser fan B4. Ratings will be on side of capacitor or outdoor
fan motor nameplate.
6-Dual Capacitor C12 (single phase)
A single dual capacitor is used for both the outdoor fan and
compressor (see unit diagram). The fan side and the compres­
sor side have different MFD ratings. See side of capacitor for
ratings,.

7-Compressor Contactor K1

In all KGB units, K1 energizes compressors B1 in response
to thermostat demand. Three phase units use three pole
double break contactors with a 24 volt coil. Single phase
units use single pole double break contactors with a 24 volt
coil.
8-Blower Delay DL3 &DL50 -074 Only
When second stage heat demand is satisfied DL3 causes a
180 second blower off delay.
DL50 causes a 1.5 second delay switching from high speed to
low speed.
9-Relay K239 -074 Units Only
Relay K239 sends the Y1 demand "G" signal to K3 (through
K250) to energize the blower on low speed and also sends the
"W1" demand "G" signal to K37 (through K250) to energize the
blower on high speed.
10-Relay K250 -074 Units Only
Relay K250 passes the "G" signal to contactor K3 energizing
the blower on low speed. On a Y2 call K250 passes the signal
to K37 energizing the blower on high speed and internal sole­
noid L34 energizing the compressor on high speed.
11-Blower Contactor K37 (074 only)
On two-speed operation K37 acts as the high speed blower
contactor and K3 acts as the low speed contactor in response
to blower demand.
12-Blower Contactor K3
On three phase units, K3 is a two pole double‐break contactor
with a 24VAC coil and on single phase units is a single pole
double break contactor with a 24 volt coil. K3 energizes the in­
door blower motor B3 in response to blower demand.
13-Condenser Fan Relay K10 (G, J voltage)
Outdoor fan relay K10 is an optional DPDT relay with a
24VAC coil. K10 energizes condenser fan B4.