Carrier 30H - Manual (Page 7)

5. Check leaving chilled water temperature to see
that it remains well above freezing.
6. Recheck compressor oil level (see Check Oil
Charge).
7. Be sure unit is fully charged (see Check Refrig­
erant Charge).
Check Refrigerant Feed Components
THERMOSTATIC EXPANSION VALVE (TXV)
One valve for each refrigerant circuit is used to
control the flow of refrigerant. The valve is
activated by a temperature sensing bulb clamped to
the suction line. The valve is factory-set to main­
tain a superheat of 8 F to 10 F.
Do not change setting
unless absolutely necessary.
FILTER-DRIER (replaceable core type)
The function of the filter-drier is to maintain a
clean, dry system. The moisture indicator (below)
can indicate any need to change the filter-drier.
Additional pressure-relief valves, properly
selected, must be field installed to protect field-
installed high side equipment as may be required by
applicable codes.
A fusible plug is factory installed on each suction
line for low-side protection. This plug will relieve
on temperature rise to 170 F.
Most local codes require that a relief valve be
vented directly to outdoors. The vent line must not
be smaller than the size of the relief valve outlet.
Check Compressor Protection Devices
CIRCUIT BREAKER
Each compressor is protected against an over-
current condition by a manual-reset calibrated-trip
circuit breaker.
iMi*i)R ! \N T; i)n not b\ pa>v connections or
increase the size ot i.nc breaker to ct.'rrcci
trouble. Determine the cause and correct before
resetting breaker.
MOISTURE-LIQUID INDICATOR
The indicator is located immediately ahead of the
TXV to provide a constant indication of the
moisture content of the refrigerant. It also provides
a sight glass for refrigerant liquid. Clear flow of
liquid refrigerant indicates sufficient charge in the
system.
Bubbles indicate under-charged system or
presence of noncondensables. Moisture in the sys­
tem,
measured in parts per million (ppm), will
change color of indicator.
Unit must be in operation at least 12 hours before
moisture indicator will give an accurate reading.
With unit running, indicating element must be in
contact with liquid refrigerant to give true moisture
indication.
At the first sign of moisture in the system, change
the filter-drier. The color BLUE indicates a safe,
dry condition and PINK shows that a dangerous
moisture level is present. The first sign of moisture
would be a
LIGHT VIOLET color.
LIQUID LINE SERVICE VALVE
This valve provides a refrigerant charging port
and, in combination with the compressor discharge
service valve, allows the refrigerant to be pumped
into the high side.
PRESSURE RELIEF DEVICES
A high-side pressure-relief valve is factory in­
stalled on each tower condenser. The valve is set to
open at a maximum pressure of 385 psig (maximum
design working pressure of the condenser).
DISCHARGE TEMPERATURE
THERMOSTAT
A sensor in the discharge side of each com­
pressor reacts to excessively high discharge gas tem­
perature and shuts off the compressor. The high
discharge gas temperature is a direct indication of
an
overtemperature condition in the motor
windings.
CRANKCASE HEATER
The heater in each compressor prevents absorp­
tion of liquid refrigerant by the oil when the
compressor is not operating.
CM ! ION; 1 :ie licalc;'. wisich is held ;n place
by
a bracket, must be tight to prevent it from
backing out of the crankcase. The heater will
burn
out if exposed to air for an extended time.
Each 125-watt electric heater is wired into the
115-volt control circuit thru the normally closed
contacts of the control relay in such a way that it is
energized
only when the compressor is not
operating.
C.\i. • ¡ON. Never ope:; any svUten or discon­
nect that -Aill de-encrei/c the crankcase heater
unlcs.s the unit Is being serxiced or will be shut
down for a proic-nged period. Alter such ser\ ice
or prolonged shutdown, cnergi/c the crankcase-
heater for 24 hours before starting the
comnrcssor.
TIME GUARD® CONTROL
This control protects the compressor against
short cycling (switch A on four-function timer).