I-Unit Components - Lennox ZHA Series Unit Information

I-UNIT COMPONENTS

The unit parts arrangement is shown in figure 1. All L1, L2,
and L3 wiring is color coded; L1 is red, L2 is yellow, and L3 is
blue. See wiring diagrams in the back of this manual for com­
plete call out of components.
A-Control Box Components
Control box components are shown in figure 2. The control
box is located in the upper portion of the compressor
compartment.
1-Disconnect Switch S48 (field installed)
Units may be equipped with an optional disconnect switch
S48. S48 is a toggle switch, which can be used by the ser­
vice technician to disconnect power to the unit.
2-Transformer T1
Units use a single line voltage to 24VAC transformer
mounted in the control box. Transformer supplies power
to CMC1 and 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
208/230V TRANSFORMER
SECONDARY
208 VOLTS
RED
230 VOLTS
PRIMARY
FIGURE 3
3-Transformer T18
T18 is a single line voltage to 24VAC transformer. T18 is
identical to T1 and is protected by a 3.5 amp circuit breaker
(CB18). T18 provides 24VAC to K1 and K2 coil and revers­
ing valve L1 and L2 (via K58-1 contacts).
4-Outdoor Fan Capacitor C1, C2, and C18
Fan capacitors C1, C2, and C18 are 370V/10MF capaci­
tors used to assist in the start up of condenser fan motors
B4, B5, and B21. Capacitor ratings will be on outdoor fan
motor nameplate.
5-Compressor Contactor K1 & K2
All compressor contactors are three‐pole‐double‐break
contactors with a 24VAC coil. K1and K2 energize compres­
sors B1 and B2 respectively in response to first or second
stage cooling demands. On CE M-volt units, contactor is
CE approved by manufacturer (Siemens). See figure 4.
6-Blower Contactor K3
Blower contactor K3, used in all units, is a three‐pole‐
double‐break contactor with a 24VAC coil used to energize
the indoor blower motor B3 in response to blower demand.
K3 is energized by a thermostat cooling demand. On M-volt
CE units, the contactor is CE approved by manufacturer
(Siemens). See figure 4.
use two primary volt­
age taps as shown in
figure 3, while 460 (G)
and 575 (J) voltage
transformers use a
single primary voltage
tap.
Page 16
CONTACTOR
FIGURE 4
7-Outdoor Fan Relay K10
Outdoor fan relay K10 is a DPDT relay with a 24VAC coil.
K10 energizes condenser fan motors B4, B5, and B21 (150
only) in response to a W1 heating or Y1 cooling demand.
8-Power Exhaust Relay K65 (PED units)
Power exhaust relay K65 is a N.O. DPDT relay with a
24VAC coil. K65 is used in units equipped with the op­
tional power exhaust dampers. K65 is energized by the
economizer control panel (A6), after the economizer
dampers reach 50% open (adjustable on control A6).
When K65 closes, the exhaust fan B10 is energized.
9-Compressor On Relays (K132 & K133)
K132 and K133 are two-pole relays with a 24V coil used
to energize compressor contactor coils. K1 is energized
by K132 with a Y1 demand. K2 is energized by K133 with
a Y2 demand. Both K1 and K2 are energized by K132
and K133 with a W1 demand.
10-Transfer Relay (K8)
K8 is a three-pole relay with a 24V coil used to de-ener­
gize the reversing valve during a heating demand. On a
first-stage demand K8-1 closes de-energizing the re­
versing valve. K8-2 closes energizing Y1 on the CMC1
board. Without K8 the reversing valve would remain en­
ergized at all times.