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15.3 - Pressure transducers
15.3.1 - Discharge pressure (circuits A & B)
This input is used to measure the high side pressure of each
circuit of the unit.
It is used to provide the pressure to replace the discharge
pressure gauge and to control the head pressure.
15.3.2 - Suction pressure (circuits A & B)
This input is used to measure the pressure of the low side of
the unit. It is used to provide the pressure to replace the suction
pressure gauge.
15.3. 3 - Oil pressure (each compressor)
This input is used to measure the oil pressure of each
compressor of the unit. It is located on the oil pressure port of
each compressor.
15.3.4 - Economizer pressure (circuits A & B)
This input is used to monitor the oil pressure differential
supplied to the compressor.
15.4 - Oil charging - low oil recharging
15.4.1 - Addition of oil charge to 30HX/GX systems
1. If the 30HXC/GX unit shuts-off repeatedly on Low oil
Level, this may be an indication of inadequate oil charge. It
could also mean simply that oil is in the process of being
reclaimed from the low-side of the system.
2. Begin by running the unit at full-load for an hour and a
half.
3. After running for 1-1/2 hours allow the unit to re-start and
run normally. If the Low Oil Level alarms persist, the unit
has a low oil charge. Add oil to the oil separator, using the
oil charging valve at the bottom of the condenser (30HXC)
or at the bottom of the oil separator (30GX).
CAUTION
Do NOT add oil at any other location as improper unit
operation may result.
4. Make sure that the unit is not running when adding oil, as
this will make the oil charging process easier. Because the
system is under pressure even when the unit is not running,
it will be necessary to use a suitable pump (hand or electric
pump) to add oil to the system.
5. Using a suitable pump, add 2 litres of Polyolester oil to the
system (CARRIER SPEC: PP47-32). Make sure that the oil
level safety switch is NOT jumpered, and allow the unit to
re-start and run normally.
6. If low oil level problems persist, add another 1 or 2 litres of
oil. If it is necessary to add more than 4 litres of oil to the
system, then contact your Carrier distributor service
department.
CAUTION: When transferring the refrigerant charge to a
storage unit, oil may be carried along when the unit is not
operating. Reuse first of all the amount of refrigerant
transferred. After draining the oil, only recharge the amount
drained (an excess oil charge may impair correct unit
operation).
15.5 - Integral oil filter change
An integral oil filter in the 06N screw compressor is specified
to provide a high level of filtration (3 µ) required for long
bearing life. As system cleanliness is critical to reliable system
operation, there is also a prefilter (7 µ) in the oil line at the oil
seperator outlet.
The replacement integral oil filter element part number is:
Carrier part number (including filter and O-ring):
06NA 660016S
15.6 - Filter change-out schedule
The filter should be checked after the first 500 hours of
operation, and every subsequent 2000 hours. The filter should
be replaced at any time when the pressure differential across
the filter exceeds 2.1 bar.
The pressure drop across the filter can be determined by
measuring the pressure at the filter service port and the oil
pressure port. The difference in these two pressures will be the
pressure drop across the filter, check valve, and solenoid valve.
The pressure drop across the check valve and solenoid valve is
approximately 0.4 bar, which should be subtracted from the
two oil pressure measurements to give the oil filter pressure
drop. The oil filter pressure drop should be checked after any
occasion that the compressor is shut down on a low oil pres-
sure safety.
15.7 - Filter change-out procedure
The following steps outline the proper method of changing the
integral oil filter.
1. Shutdown and lockout the compressor.
2. Manually force the operation of the oil solenoid valve, in
order to press the internal valve shutter onto its seat.
3. Close the oil filter service valve. Bleed pressure from the
filter cavity through the filter service port.
4. Remove the oil filter plug. Remove the old oil filter.
5. Prior to installing the new oil filter, “grease” the o-ring with
oil. Install the filter and replace the plug.
Before closing up the lube oil system, take the opportunity
to replace the prefilter, as well.
6. When complete, evacuate the filter cavity through the filter
service port. Open the filter service valve. Remove any
compressor lockout devices, the compressor is ready to
return to operation.
15.8 - Compressor replacement
15.8.1 - Compressor rotation control
Correct compressor rotation is one of the most critical applica-
tion considerations. Reverse rotation, even for a very short
duration, damages the compressor.
The reverse rotation protection scheme must be capable of
determining the direction of rotation and stopping the
compressor within 300 milliseconds. Reverse rotation is most
likely to occur whenever the wiring to the compressor
terminals is disturbed.
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