Carrier 50BA - Manual (Page 18)

Refer to Fig. 28 for field control wiring to pump
relay (50BA unit), condenser fan relay (5ÛBB unit)
and remote thermostat (unit sizes 016 thru 064).
On 50BA,BB004 thru 012 units, the thermostat is
factory installed with a sensing bulb in the return
air. To wire these units to a remote thermostat, or
to a remote control switch and thermostat, refer to
unit Wiring book or contact your Carrier
representative.
On 50BA,BB016 thru 064 units, a field-supplied
thermostat must be installed (Fig. 28). Table 9 lists
the recommended connecting sequence for a 2-step
thermostat.
Table 9 — Two-Step Thermostat Connection
for Capacity Control
UNIT THERMO TERMINAL COMPONENT
50BA.BB STEP CONN. ENERGIZED
012 One 2 Compressor
016 Two 3 Liquid line solenoid
024
028
034
One 3 Compressor No 2
Two 2 Compressor No 1
044 One 3 and 5 Compressor No 2 and 3
054 Two 2 Compressor No 1
064
One 3 and 6
Capacity control solenoid
valve and liquid line
solenoid valve No 2
and compressor No 2
Two 2
Liquid line solenoid No 1
and compressor No 1
FREEZE-PROTECTION THERMOSTAT — An
accessory freeze-protection thermostat is required
on Size 008,012 and 064 units when the low-pressure
switch setting (Table 1) is lowered or when a liquid
line low-pressure switch is installed for intermediate
or cold-weather operation. Installation instructions
are shipped with the thermostat.
HEATING COILS — Accessory heating coils are
available for field installation. Separate installation
instructions are shipped with the accessory.
START-UP
Unit Size 50BA,BB004 and 006
1. Set selector switch at OFF and thermostat at
highest setting.
2. Turn on unit power. On 50BB units, check that
crankcase heater is on. Compressor shell in
vicinity of heater should become warm to the
touch.
3. On 50BA unit, turn on condenser water supply.
On 50BB unit, open refrigerant line service
valves.
4. Set selector switch at FAN position. Check fan
speed (Table l)and rotation. Fan direction arrow
is attached to fan scroll. If fan requires adjust­
ment, refer to Service section entitled, Indoor
Air Fan Adjustment.
5. On 50BA (water-cooled) units, set selector switch
on COOL and thermostat at lowest setting.
Compressor will start within 5 minutes.
On 50BB (condenserless) units, allow crankcase
heater to remain energized (unit power on) for at
least 6 - 8 hours; then set selector switch on
COOL and thermostat at lowest setting. Com­
pressor will start within 5 minutes.
6. Set thermostat at highest setting to shut off
compressor.
7. Set thermostat at lowest setting. Compressor will
start within 5 minutes as described in the Service
section, Time Guard® Control Circuit.
On 50BB remote condenser unit, the outdoor air
fans cycle with compressor.
8. Set thermostat for comfort as desired.
^TO SHUT DOWN UNIT — Set selector switch at
OFF. Do not shut off main power except to service
unit. Crankcase heater (50BB unit) is operative only
when unit power is on (see Service section, Crank­
case Heaters).
Unit Size 50BA.BB008 thru 064
1. Thoroughly clean and inspect unit.
2. Open compressor discharge and suction service
valves and liquid shutoff valves.
3. With selector switch in OFF position, turn circuit
breakers on. On 50BA008 and 064 unit, and
on all 50BB units, leave unit in this condition for
24 hours so that crankcase heater can drive off
any accumulated refrigerant.
4. Turn selector switch to COOL. Time Guard
circuit will delay unit start for 5 to 6 minutes.
5. Set thermostat at desired comfort temperature.
TO SHUT DOWN UNIT
1. If unit may be exposed to freezing temperatures,
drain water from condenser and all water piping.
2. Add a noncorrosive antifreeze to any residual
water in the system.
3. Turn selector switch to OFF position and turn
circuit breakers off.
4. If unit is to be used for winter heating, leave
circuit breakers on, set selector switch at FAN
position and turn cooling thermostat off.
Service Valves — Always be sure that compressor
suction and discharge service valves and liquid
shutoff valves are open before operating unit.
The liquid shutoff valves are accessible from the
rear of Size 064 unit and from front or rear of all
other units. To open valve, turn counterclockwise
(backseat). After opening, replace and tighten valve
cap to prevent leakage.
^Capacity Control Valve Adjustment (Fig. 29)
The capacity control valves are factory set as indi­
cated in Table 10. If valve adjustment is required,
for any reason, use the following procedures.
The control set point (cylinder load point) is
adjustable from 0 psig to 85 psig. The pressure
differential between the cylinder load point and
cylinder unload point is adjustable from 6 psig to
22 psig (see Table 10).
t
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