Specifications

57
MAINTENANCE
Refrigerant Charging - Adding Charge
IMPORTANT
These units are designed for use with R-134a only. DO NOT
USE ANY OTHER refrigerant in these units.
CAUTION
When adding or removing charge, circulate water through the
condenser (HX) and cooler at all times to prevent freezing.
Freezing damage is considered abuse and may void the Carrier
warranty.
CAUTION
DO NOT OVERCHARGE system. Overcharging results in
higher discharge pressure with higher cooling fluid
consumption, possible compressor damage and higher power
consumption.
Indication of low charge on a 30HXC system
NOTE
To check for low refrigerant charge on a 30HXC, several factors
must be considered. A flashing liquid-line sightglass is not
necessarily an indication of inadequate charge. There are many
system conditions where a flashing sightglass occurs under
normal operation. The 30HXC metering device is designed to
work properly under these conditions.
1. Make sure that the circuit is running at a full-load condition.
To check whether circuit A is fully loaded, enter <3> <STAT>
on the HSIO keypad. The display will read “CIRCUIT A
ANALOGUE VALUES”. Using the down arrow key on the
keypad, scroll down once to “Total Capacity”. If this value is
100 %, the circuit is at full-load. To check circuit B, follow
the same procedure, but enter <5> <STAT> on the keypad.
2. It may be necessary to use the Manual Control feature to force
the circuit into a full-load condition. If this is the case, see the
instructions for using the Manual Control feature (Keypad
Directory) <8> <SRVC>.
3. With the circuit running at full-load, verify that the cooler
leaving fluid temperature is in the range of 5.6 - 7.8 °C.
4. At this condition, observe the refrigerant in the liquid line
sightglass. If there is a clear sightglass, and no signs of
flashing, then the circuit is adequately charged. Skip the
remaining steps.
5. If the refrigerant appears to be flashing, the circuit is probably
low on charge. Verify this by checking the EXV Percent Open.
This information can be accessed by entering <3> <STAT>
on the HSIO keypad for circuit A, or <5> <STAT> for circuit
B. Scroll down using the down arrow key on the keypad, until
EXV Percent Open is displayed.
6. If the EXV Percent Open is greater than 60 %, and the liquid-
line sightglas is flashing, then the circuit is low on charge.
Follow the procedure for adding charge.
To add charge to the 30HXC systems
1. Make sure that the unit is running at full-load, and that the cooler
leaving fluid temperature is in the range of 5.6 - 7.8 °C.
2. At these operating conditions, check the liquid-line sightglass.
If there is a clear sightglass, then the unit has sufficient charge.
If the sightglass is flashing, then check the EXV Percent Open.
If this is greater than 60 %, then begin adding charge.
NOTE
A flashing liquid-line sightglass at operating conditions other
than those mentioned above is not necessarily an indication of
low refrigerant charge.
3. Add 2.5 kg of liquid charge into the cooler using the charging
valve located on the top of the cooler.
4. Observe the EXV Percent Open value. The EXV should begin
closing as charge is being added. Allow the unit to stabilize. If
the EXV Percent Open remains above 60 %, and the sightglass
continues flashing, add an additional 2.5 kg of liquid charge.
5. Allow the unit to stabilize, and again check the EXV Percent
Open. Continue adding 2.5 kg of liquid refrigerant charge at
a time, and allow the unit to stabilize before checking the
EXV position.
6. When the EXV Percent Open is in the range of 40 - 60 %,
check the liquid line sightglass. Slowly add enough additional
liquid charge to ensure a clear sightglass. This should be done
slowly to avoid overcharging the unit.
7. Verify adequate charge by continuing to run at full-load with
5.6 - 7.8 °C cooler leaving fluid temperature. Check that the
refrigerant is not flashing in the liquid-line sightglass. The
EXV Percent Open should be between 40 and 60 %. The cooler
level indicator should be in the range of 1.5 - 2.5.
Indication of low charge on 30GX systems
1. Make sure that the circuit is running at a full-load condition
and all condenser fans are energized and running at full speed.
To check whether circuit A is fully-loaded, enter <3> <STAT>
on the HSIO keypad. The display will read “CIRCUIT A
ANALOGUE VALUES”. Using the down arrow key on the
keypad, scroll down once to “Total Capacity”. If this value is
100 %, the circuit is at full-load. To check circuit B, follow
the same procedure, but enter <5> <STAT> on the keypad.
2. It may be necessary to use the Manual Control feature to force
the circuit into a full-load condition. If this is the case, see the
instructions for using the Manual Control feature (Keypad
Directory) <8> <SRVC>.
3. With the circuit running at full-load, verify that the cooler
leaving fluid temperature is in the range of 5.6 - 7.8 °C.
4. Measure the air temperature entering the condenser coils.
Measure the liquid temperature after the tee where the two
coil liquid lines join. The liquid temperature should be 8.3°C
above the air temperature entering the coils. If the difference
is more than this and the sightglass is flashing, the circuit is
uncharged. Proceed to step 5.