J.
Compressor PTC Overload Protection
The control senses the resistance of the compressor internal
positive temperature coefficient (PTC) overloads. If PTC resis-
tance is out of range, control shuts off the unit until resistance
range is acceptable. See Table 8 for compressor PTC ranges.
When the control turns outdoor unit off due to out of range PTCs,
the unit remains off for 15 minutes with outdoor fan running. After
15 minutes, the control checks resistance every 5 minutes until it
reaches the reset range. During this time, a malfunction signal
appears at control board. If a PTC trip occurs 3 times, the control
locks out outdoor unit operation and provides a malfunction signal
at control and indoor thermostat.
K.
Pressure Switch Protection
The outdoor unit is equipped with high- and low-pressure
switches, wired in series. If the control senses the opening of a
pressure switch, it provides a 5-minute time delay in outdoor unit
operation with outdoor fan running. A malfunction signal appears
on control when pressure switch opens. If pressure switch remains
open for 1 hr or longer, a malfunction signal is provided at L
terminal on indoor thermostat.
WARNING:
Interlocked contactor coils are 240v, high
voltage. Electrical shock can cause personal injury or
death.
CAUTION:
Do not bypass interlocks of contactors, as
compressor damage will occur.
L.
Major Components
2-SPEED CONTROL
The 2-speed control board controls the following functions:
- High- and low-compressor contactor operation
- Outdoor fan motor operation
- Crankcase heater operation
- Compressor protection
- Pressure switch monitoring
- Second-stage latching
- Time delays
- 5-minute time delay speed-up (bypass)
Refer to the System Functions section for individual function
information.
HEADER PIN HOUSING
The header pin housing is the plastic assembly which holds the
stripped lead ends for field connections. The 2-speed control
receives 24-vac low-voltage control system inputs through the
housing/pins. The housing also contains jumpers which the control
uses for system configuration, such as heat pump versus air
conditioner. Refer to Fig. 11 for header pin housing configuration.
2-SPEED COMPRESSOR
The 2-speed compressor contains motor windings that provide
low-speed, 4 pole (1750 RPM) and high-speed, 2-pole (3500
RPM) operation. Refer to Table 9 for appropriate winding resis-
tances. Refer to unit wiring label for winding configurations.
The 2-speed compressor is protected by an internal pressure relief
(IPR) which relieves discharge gas into compressor shell when
differential between suction and discharge pressures exceeds 500
psi.
The compressor is also protected by 3 PTC devices attached to
motor windings. The PTC resistance is sensed by the 2-speed
control. See Table 8 for resistance ranges.
Fig. 9—LED and Potentiometer Location
A91503
HIGH VOLTAGE
LOW VOLTAGE
L2
LO
HI
CCH
ODF
O
C
LM1 LM2
DFT1 DFT2 T1
T2
S2
S1
PW2 PW1
P1
1
18
SPEED-UP
STAGE 2
LATCH
DEFROST
TIME
BALANCE
POINT
K7
K6
K5
K4
K3
K2
K1
LED 1
Fig. 10—Typical Cooling Balance Points
A91282
10
20
30
40
50
60
70
50
60
70
80
90
100
110
120
BTU (1000'S)
HIGH SPEED CAPACITY
HIGH SPEED
BALANCE POINT
LOW SPEED
BALANCE POINT
LOW SPEED CAPACITY
TEMPERATURE (°F)
STRUCTURE
BALANCE POINT
TABLE 8—COMPRESSOR PTC RANGES
COMPRESSOR INTERNAL PTC RESISTANCE
Safe range (77°F)
1.5k to 7.8k ohms
To trip
26k to 34k ohms
To reset
8.4k to 10k ohms
Fig. 11—Header Pin Housing Configuration
A93565
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
C - TRANSFORMER COMMON
R - TRANSFORMER LINE
Y2 - SECOND STAGE COOLING
L - MALFUNCTION LIGHT
Y1 - FIRST STAGE COOLING
—15—
