Maintenance; Refrigerant Charging - Adding Charge; Indication Of Low Charge On A 30Hxc System - Carrier 30HXC Series Installation, Operation And Maintenance Instructions

15 - MAINTENANCE

15.1 - 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.

15.2 - 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 condi-
tion. To check whether circuit A is fully loaded, follow the
procedure described in the Controls manual.
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 in
the Controls manual.
3. With the circuit running at full-load, verify that the cooler
leaving fluid temperature is in the range of 6°C ± 1.5.
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
position (see Controls IOM).
6. If the opening position of the EXD is greater than 60%, and
if the liquid-line sightglass is flashing, then the circuit is
low on charge. Follow the procedure for adding charge.
15.2.1 - 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 EXD 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 evaporator using the
charging valve located on the top of the evaporator.
4. Observe the EXD Percent Open value. The EXD should
begin closing as charge is being added. Allow the unit to
stabilize. If the EXD Percent Open remains above 60%, and
there are still bubbles in the sightglass, add an additional
2.5 kg of liquid charge.
5. Allow the unit to stabilize, and again check the EXD
Percent Open. Continue adding 2.5 kg of liquid refrigerant
charge at a time, and allow the unit to stabilize before
checking the EXD position.
6. When the EXD 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 6°C ± 1.5 evaporator leaving fluid temperature. Check
that the refrigerant is not flashing in the liquid-line
sightglass. The EXD Percent Open should be between 40
and 60%. The cooler level indicator should be in the range
of 1.5 - 2.5.
15.2.2 - Indication of low charge on 30GX systems
1. Make sure that the circuit is running at a full-load condition
and that the condensing temperature is 50°C ± 1.5. To
check whether circuit A is fully-loaded, follow the
procedure in the Controls IOM.
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 function
(procedure in the Controls IOM).
3. With the circuit running at full-load, verify that the cooler
leaving fluid temperature is in the range of 6°C ± 1.5.
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.
5. Add 2.5 kg of liquid charge into the cooler using charging
valve located in the top of the cooler.
6. Allow the system to stabilize and then recheck the liquid
temperature. Repeat step 5 as needed allowing the system
to stabilize between each charge addition. Slowly add
charge as the sightglass begins to clear to avoid over-
charging.
15.2.3 - Space temperature, outdoor air temperature
(optional)
These temperatures are used to measure the temperature of the
space or the outside air temperature respectively for reset
control based on Outside Air or Space Temperature reset
options.
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