Factory Defaults; Major Components - Bryant R-22 Application Manual And Service Manual

TWO SPEED
THERMOSTAT
W2
Fig. 36—Low-Voltage Control Wiring
AUXILIARY HEAT (W2) LOCKOUT
In some areas, it is necessary to disable the auxiliary heat, except
for defrost, until the outdoor ambient is less than the structure's
balance point. This is accomplished by using the low-voltage
wiring as shown in Fig. 36. Wire the 24vac W2 signal from the
indoor thermostat to W3 of the control, and W2 of the control to
W2 of the indoor unit. When the outdoor ambient is less than the
setting of the balance-point POT, the 24vac signal energizes the
auxiliary heat (W2) of the indoor unit.
EMERGENCY HEAT
If the 2-speed control receives a call for auxiliary heat (W2)
without a heat-pump heating (Y1) call, the second auxiliary stage
(W3) is energized. This ensures all available heat is energized if
the indoor thermostat is switched to emergency heat.
COMPRESSOR PTC-OVERLOAD PROTECTION
The control senses the resistance of the compressor internal
positive-temperature coefficient (PTC) overloads. If the resistance
of the PTCs is out of range, the control shuts off the unit until the
resistance range is acceptable. See Table 16 for compressor PTC
ranges.
TABLE 16—COMPRESSOR PTC RANGES
COMPRESSOR INTERNAL-PTC RESISTANCE
Safe Range (77°F)
To trip
To reset
When the control turns off the outdoor unit due to out-of-range
PTCs, the unit remains off for 15 minutes with the outdoor fan
running. After 15 minutes, the control checks the resistance every
5 minutes until it reaches the reset range. During this time, a
malfunction signal appears on the control board. If this happens,
remove the wires on control board at S1 and S2 and measure the
resistance across the leads. When the resistance reaches 8,400 to
10,000 ohms, system operation may be resumed. If the resistance
remains outside this range, a quick check of the leads at the
compressor should be made. Loose connections can cause inaccu-
rate readings. If a PTC trip occurs 3 times, the control will lock out
the outdoor-unit operation and provide malfunction signals at both
the control and indoor thermostat.
FAILED COMPONENT
Ambient Thermistor
Outdoor Coil Thermistor
Furnace Interface Jumper
FAN TWO SPEED
COIL HEAT PUMP
W2 W2
CONTROL
W3
LOGIC
W3
A93572
1.5k to 7.8k ohms
26k to 34k ohms
8.4k to 10k ohms
TABLE 17—FACTORY DEFAULTS
Crankcase Heater
Second-Stage Latching
Furnace Interface
Heating Switchover Speed Point
Defrost Initiation
Outdoor Thermostat for
Auxiliary Heat
Defrost Initiation and Termination
Furnace Interface
PRESSURE SWITCH PROTECTION
The outdoor unit is equipped with high- and low-pressure
switches, wired in series. If a pressure switch opens, the control
provides a 5-minute time delay in outdoor unit operation with the
outdoor fan running. A malfunction signal appears on the control
when a pressure switch opens. If the switch remains open for 1 hr
or longer, a malfunction signal is provided at the L terminal of the
indoor thermostat.
III. FACTORY DEFAULTS
Factory defaults have been provided in the event of failure of the
ambient thermistor, outdoor-coil thermistor, and/or furnace inter-
face jumper. Refer to Table 17 for default and function.
IV. MAJOR COMPONENTS
TWO-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 speedup (bypass)
Heat pumps:
• Time/temperature defrost
• Defrost-interval selection
• Furnace interface
• Electric-heat staging
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 the 24vac 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. See Fig. 37 for header-pin housing configurations.
TWO-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 Fig. 38 to determine which windings are
energized at each speed. Refer to Compressor Winding-Check
section under Troubleshooting and Table 18 for appropriate
winding resistances.
The 2-speed compressor is also protected by an internal-pressure
relief (IPR), which relieves discharge gas into the compressor shell
(low side) when the differential between suction and discharge
FUNCTION
—33—
DEFAULT
Energized during any off cycle
Does not function
Balance point does not function, but
interface still energizes furnace and
locks out heat pump with a call for W2
Unit only runs in high-
compressor speed
Defrost is initiated based on coil
temperature only
Anytime there is a call for W2,
W3 is also energized.
Defrost occurs at each time interval,
but terminates after 5 minutes
Does not function