Specifications

7
Table 5-PRESSURE SWITCH SPECIFICATIONS
CUTOUT CUTIN
UNIT30
Psig Kpa Psig Kpa
Low Pressure
42±3 290±21 57±5 393±34
CUTOUT CUTIN
High Pressure
Psig Kpa Psig Kpa
HR
280±10 1931±69 180±20 1241±138
HS
375±10 2585±69 275±20 1896±138
OIL PRESSURE SAFETY SWITCH
Standard on 30HS units, accessory for 30HR (see Fig. 2 for
wiring connections). To test, bypass pressure switch with
jumper. Compressor should stop in about 120 seconds. If it
continues to run for more than one minute, and nothing is
wrong with the wiring, replace switch. Be sure differential
switch closes when compressor stops. Switch setting requires
pressure rise to 9 psig in 120 seconds and oil pressure above 4
psig for compressor operation. After test, allow 5 minutes for
thermal switch to cool, then press reset button.
If the safety switch stops the compressor, find trouble and
correct before attempting to restart.
Fig 2-Oil Pressure Safety Switch Connection Diagram
COMPRESSOR THERMAL PROTECTION
A discharge thermostat installed in one cylinder head of
each compressor, senses an over temperature condition. If the
discharge gas temperature of any compressor exceeds
295

5F,the thermostat opens and shuts off that compressor
and the other compressor in the circuit. The thermostat reset
temperature is approximately 250 F. See Fig.3 For switch
connections.
4
4
2 1
2 3
CR
1
CR
2
D T
1
DT
2
T B
3
T B
4
CI R C U IT N o
.
2
DT - Discharge Temperature Switch
TB - Terminal Block (unit)
- Terminal on unit terminal block
- Terminal Connections (Marked)
Fig3-Discharge Temperature Switch Connections.
MOISTURE-LIQUID INDICATOR
Clear flow of liquid refrigerant indicates sufficient
charge in system. Bubbles indicate under-charged system or
presence of non-condensable. Moisture, measured in parts per
million (PPM), in system will change color of indicator.
Green moisture is below 330 PPM: chartreuse (caution) 380 to
550 yellow (wet)- above 550 change filter-drier cores at first
sign of moisture in system. Each refrigerant circuit has an
indicator.
With unit running, indicating element must be in contact
with liquid refrigerant to give true moisture indication. 30HS
units (shipped holding charge only) must be fully charged and
run before moisture content can be determined.
LIQUID LINE SOLENOID VALVE
One valve in each refrigerant circuit prevents liquid
refrigerant from migrating to cooler during shut down.
ELECTRICALLY EXPANSION VALVES
These valves control flow of liquid refrigerant by
maintaining constant superheat of vapor leaving cooler.
Factory set to maintain a superheat of 6C; do not adjust setting
unless absolutely necessary. There is one valve for each
refrigerant circuit. See catalogue for more details.
THERMAL EXPANSION VALVES
These valves control flow of liquid refrigerant by
maintaining constant superheat of vapor leaving cooler.
Factory set to maintain a superheat of 8-10 F; do not adjust
setting unless absolutely necessary. There is one valve for
each refrigerant circuit.
CAPACITY CONTROL
Capacity control is a system, which cycles compressors
as well as loads and unloads cylinders in each compressor to
maintain load requirements. Includes a 4-step temperature
controller and two cylinder bank unloadeds. Table 6 shows
capacity control steps.
Four-Step Temperature Controller consists of four load
switches actuated by pressures developed in a temperature-
sensing bulb located in the return water nozzle of the chilled
water system. The controller is factory set to control from
return water temperature thru a cooling range of 10 F.
The sequence switches are factory calibrated and sealed
and should not require any field changes.
If a different return-water cooling range or a leaving-
water control is specified, or if brine is to be used the
controller must be changed. Consult local Carrier
representative for proper control device.
The temperature at which the last step of capacity
unloads indicated by the design set point on the adjustable dial
(Fig. 4). Example: design set point is at 44 F. On a reduction
in load, the Capacity of the unit will be reduced to zero when
return water temperature drops to 44 F.
WARNING: Any alteration of factory settings, except design
set point, without Carrier authorization may void the Carrier
Warranty.