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Refrigerant Charging/Adding Charge
Indication of low charge on a system:
NOTE: To check for low refrigerant charge on a 30HXC unit,
several factors must be considered. A flashing liquid line sight
glass (located in the EXV body) is not necessarily an indica-
tion of inadequate charge. There are many system conditions
where a flashing sight glass occurs under normal operation.
The EXV 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, enter the
Outputs mode from the Navigator and then sub-mode
‘CIR.A’ or ‘CIR.B’ depending on the circuit under inves-
tigation. The circuit is fully loaded if its compressor and
loader relays all show ‘On’.
2. It may be necessary to use the Service Test feature to
force the circuit into a full-load condition. If this is the
case, see the instructions for using the Service Test
feature in Table 13 of this manual.
3. With the circuit running at full load, verify that the cooler
leaving fluid temperature is in the range of 38 to 46 F
(3.3 to 7.8 C). Check temperature drop across liquid line
strainer/drier. Maximum allowable temperature drop
is 3° F (1.7° C). Strainer is cleanable if necessary and
contains 1 standard drier core on all 30GX and 30HXA,C
161-271 models.
4. At this condition, observe the refrigerant in the liquid line
sight glass. If there is a clear sight glass, 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 is located under the
sub-mode ‘CIR.A’ or ‘CIR.B’ (Outputs mode) and is
shown as items ‘EXV.A’ and ‘EXV.B’ Scroll through the
Navigator until the desired item is located.
6. If the EXV Percent Open is greater than 60%, and the
liquid line sight glass is flashing, then the circuit is low on
charge. Follow the procedure for adding charge for
30HXC units.
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 42 to
46 F (5.6 to 7.8 C).
2. At these operating conditions, check the liquid line sight
glass. If there is a clear sight glass, then the unit has
sufficient charge. If the sight glass is flashing, then check
the EXV Percent Open. If this is greater than 60%, then
begin adding charge.
NOTE: A flashing liquid line sight glass at operating
conditions other than those mentioned above is not neces-
sarily an indication of low refrigerant charge.
3. Add 5 lb (2.3 kg) of liquid charge into the cooler using
the fitting located on the tube entering the bottom of the
cooler. This fitting is located between the Electronic
Expansion Valve (EXV) and 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 sight glass continues flashing, add an additional
5 lb (2.3 kg) of liquid charge.
5. Allow the unit to stabilize, and again check the EXV
Percent Open. Continue adding 5 lb (2.3 kg) at a time of
liquid refrigerant charge, and allow the unit to stabilize
before checking the EXV position.
6. When the EXV Percent Open is in the range of 40 to
60%, check the liquid line sight glass. Slowly add enough
additional liquid charge to ensure a clear sight glass. This
should be done slowly to avoid overcharging the unit.
7. Verify adequate charge by continuing to run at full load
with 42 to 46 F (5.6 to 7.8 C) cooler leaving fluid temper-
ature. Check that the refrigerant is not flashing in the
liquid-line sight glass. The EXV Percent Open should be
between 40 and 60%.
To add charge to the 30GX and 30HXA systems:
1. Make sure that the circuit is running at a full load condi-
tion and all condenser fans are energized and running on
the keypad, at the appropriate line on the display. To
check whether circuit A is fully loaded, enter the Outputs
mode from the Navigator and then sub-mode ‘CIR.A’ or
‘CIR.B’ depending on the circuit under investigation. The
circuit is fully loaded if its compressor and loader relays
all show ‘On’.
2. It may be necessary to use the Service Test feature to
force the circuit into a full-load condition. If this is the
case, see the instructions for using the Service Test
feature in Table 13 of this manual.
3. With the circuit running at full-load, verify that the cooler
leaving fluid temperature is in the range of 38 to 48 F (5.6
to 7.8 C).
4. For 30HXA chillers, raise the compressor discharge to
approximately 125 F (51.7 C) saturated condensing tem-
perature (185 psig [1276 kPa]). For 30GXN,R chillers,
raise the compressor discharge to approximately 130 F
(54.4 C) saturated condensing temperature (198 psig
[1366 kPa]). Measure the liquid temperature entering the
EXV for 30HXA units. For 30GXN,R units, measure the
liquid temperature after the tee where all liquid lines have
joined (see Fig. 28 and 29). The liquid temperature
should be approximately 107 F (41.7 C) for optimum
charge. If the temperature is greater than 107 F (41.7 C)
and the sight glass is flashing, the circuit is undercharged.
5. Add 5 lb (2.3 kg) of liquid charge into the cooler using
the fitting located on the tube entering the bottom of the
cooler. This fitting is located between the Electronic
Expansion Valve (EXV) and 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 sight glass begins to clear to avoid
overcharging.
IMPORTANT: These units are designed for use with
R-134a only. DO NOT USE ANY OTHER REFRIG-
ERANT in these units without first consulting your
Carrier representative.
When adding or removing charge, circulate water through
the condenser (30HXC) and cooler at all times to prevent
freezing. Freezing damage is considered abuse and may
void the Carrier warranty.
DO NOT OVERCHARGE system. Overcharging results
in higher discharge pressure with higher cooling fluid
consumption, possible compressor damage and higher
power consumption.