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I-APPLICATION
CHA/CHP16/20 2, 2 1/2 and 3 ton units are in the one cabiĆ
net size. CHA/CHP16/20 3.5, 4 and 5 ton units are also one
in one cabinet size. All CHA/CHP16/20 model units are apĆ
plicable for commercial, single or three phase installations.
CHA/CHP16/20 models are factory equipped with the hardĆ
ware required for installing Lennox' optional thermostat conĆ
trol systems like the T7300 or T8600 (refer to the EngineerĆ
ing Handbook for more specific application data).
II-UNIT COMPONENTS
CHA/CHP16/20 unit components are shown in figure 1.
A-Control Box Components
CHA/CHP16/20 control box is shown in figure 2. The control
box is located adjacent to the compressor compartment, beĆ
hind the control box access panel in front of the unit.
The condenser fan can be accessed by removing the fan
grill located on top of the unit.
The indoor blower access panel (all units) is located on the
opposite side of the unit from the heating compartment acĆ
cess.
1-Transformer T1
All CHA/CHP16/20 series units use a single line voltage to
24VAC transformer mounted in the control box. The transĆ
former supplies power to control circuits in the unit. TransĆ
formers are rated at 70VA and use two primary voltage taps
as shown in figure 3. T1 is protected by a 3.5 amp circuit
breaker (CB8).
BLUE
YELLOW
ORANGE
RED
BLACK
240 VOLTS
208 VOLTS
PRIMARY
SECONDARY
208 / 240 VOLT TRANSFORMER
FIGURE 3
24 VOLTS
2-Cooling Contactor K1
K1 is a 24V to line voltage contactor used to energize the
compressor and condenser fan in response to thermostat
demand. Three-phase units use three-pole double-break
contactors. Single-phase units use single-pole contactors.
DANGER
Single -phase units use single
pole contactors. One leg of comĆ
pressor, capacitor and condensĆ
er fan are connected to line voltĆ
age at all times.
Remove all power to disconnect
before servicing.
Electrical shock resulting in
death or injury may result if
power is not disconnected.
NOTE-Contactor K1 is energized by the thermostat
control system. Depending on the control system
installed, the contactor may or may not be immediately
energized upon demand.
3-Indoor Blower Relay K3 (Cooling Speed)
208/230 volt units use a single DPDT relay to energize the
indoor blower motor. 460 volt and 575 volt units use a single
3PDT relay.
CHP16/20 units
(singleĆphase and threeĆphase) use a
conventional 2 heat / 2 cool thermostat.
Transfer relay
K8 is used to direct power to blower relay K3 depending on
whether the unit is in cooling or heating mode. In cooling
mode transfer relay K8 is deĆenergized and blower relay K3
is energized by thermostat terminal G through K8Ć1 normalĆ
ly closed contacts. In heating mode transfer relay K8 is enĆ
ergized and blower relay K3 is energized directly by transĆ
former T1 through K8Ć1 normally open contacts.
460 (G) voltage units use a unique blower motor which reĆ
quires the 3PDT relay. The motor utilizes the extra set of
N.C. relay contacts to complete an internal circuit when the
motor is on heating speed. Refer to the blower motor section
of this manual for more information.
4-Defrost Relay K4 (CHP Models Only)
Relay K4 initiates defrost in response to demand. K4 is enĆ
ergized when defrost thermostat S6 closes and defrost conĆ
trol CMC1 calls for defrost. Once energized, contacts K4Ć1
open to reset the internal timer to zero, contacts K4Ć2 close
to energize the electric heat (if installed) and K4Ć3 closes to
latch condenser fan relay K10 and defrost relay K4 through
defrost cycle.
