Control Box Components; Defrost Relay - Lennox HP21 Unit Information

START CAPACITOR C7
(single-phase only)
OUTDOOR FAN CAPACITOR C1
(three-phase only)
DUAL CAPACITOR C12
(single−phase)
EARLY HP21 -1 / -2 / -3 SINGLE PHASE SERIES UNITS USE FAN
CAPACITOR C1 AND COMPRESSOR CAPACITOR C5 IN PLACE OF
C12
Contactor K1
Contactor K1 energizes low speed compressor operation
in all units (single-phase and three-phase.) In single−phase
units K1 is a two pole contactor with two sets of normally
open contacts and in three−phase units K1 is a five pole
contactor with three sets of normally open contacts and two
sets of normally closed contacts. K1 is also equipped with a
set of single-pole double-throw auxiliary contacts located
on the side of the contactor. The contactor is energized in
response to low speed thermostat demand (from two-
speed control jackplug J44/P44 pin 9.)
TABLE 2
Compressor Speed
Low
High
In single-phase units, K1 also de-energizes the crankcase
heater during compressor operation.
Contactor K69
Contactor K69 energizes high speed operation in all units
(single-phase and three-phase.) In single−phase units K69
is a five−pole contactor with three sets of normally open
contacts and two sets of normally closed contacts. In three−
phase units K69 is a three−pole contactor with three sets of
normally open contacts.This contact arrangement pro-
vides unique switching characteristics for two-speed
operation. K69 is also equipped with a set of single-pole
double-throw auxiliary contacts located on the side of the
contactor. The contactor is energized in response to high
speed thermostat demand from JP44-8 (two-speed control
jackplug J44/P44 pin 8.)
HP21 CONTROL BOX COMPONENTS
START RELAY K31
CONTACTOR K69
(single-phase only)

DEFROST RELAY

Contactors Energized
Single-Phase Three-Phase
K1 K1
K1 & K69 K69
CONTACTOR K1
TRANSFORMER
T19
K4
FIGURE 2
Contactor Operation: Single-Phase Units
Low speed demand energizes K1. K1 de-energizes the
crankcase heater and energizes the compressor. High
speed demand energizes both contactors K1 and K69. K69
N.O. contacts close to redirect the circuit to the high speed
start windings and the N.C. contacts open to de-energize
the low speed start windings. K69 N.C. contacts also switch
whenever K69 is energized to ensure that K1 is energized
with K69 during high speed operation (refer to unit wiring
diagram).
Contactor Operation: Three-Phase Units
Low speed demand energizes K1. K1 energizes the com-
pressor and locks out contactor K69. High speed demand
de−energizes K1 and energizes contactor K69. K69 locks
out K1 and energizes the compressor on high speed.
K1 is wired so that when de−energized, the contactor forms
a parallel common connection to the motor windings for
high speed forming a parallel Delta" connection for Cope-
land compressors. When K1 is energized, the contactor
forms a series Delta connection to the compressor wind-
ings. Refer to operation sequence in back of this manual for
more information.
C−Defrost Relay K4
All HP21 units are equipped with a defrost relay located
in the unit control box which controls defrost. The relay is
a 3PDT relay powered 24 VAC from the thermostat. K4 is
enabled during both cooling and heating modes (except
emergency heat). It is only powered when the defrost
control is calling for defrost. When energized, the revers-
ing valve and indoor auxiliary heat are energized.
Simultaneously, the outdoor fan is de-energized. K4
latches in for the duration of the defrost period.
Page 4
TWO-SPEED CONTROL
DEFROST CONTROL
CMC1
SPEED CONTROL
24V TERMINAL
THERMOSTAT S55
STRIP TB15
A14