Carrier 48TC series, Инструкции по обслуживанию и техническому обслуживанию, Страница: 17 / 112

17
Refrigerant System Pressure Access Ports
There are two access ports in the system: on the suction tube near
the compressor, and on the discharge tube near the compressor.
These are brass fittings with black plastic caps. The hose connec -
tion fittings are standard
1
/
4
-in. SAE male flare couplings. See
Fig. 15.
The brass fittings are two-piece High Flow valves, with a recepta -
cle base brazed to the tubing and an integral spring-closed check
valve core screwed into the base. See Fig. 15. This check valve is
permanently assembled into this core body and cannot be serviced
separately; replace the entire core body if necessary. Service tools
are available from RCD that allow the replacement of the check
valve core without having to recover the entire system refrigerant
charge. Apply compressor refrigerant oil to the check valve core’s
bottom O-ring. Install the fitting body with 96 ±10 in.-lb of torque;
do not overtighten.
PURON ® (R-410A) REFRIGERANT
This unit is designed for use with Puron (R-410A) refrigerant. Do
not use any other refrigerant in this system.
Puron (R-410A) refrigerant is provided in pink (rose) colored cyl -
inders. These cylinders are available with and without dip tubes;
cylinders with dip tubes will have a label indicating this feature.
For a cylinder with a dip tube, place the cylinder in the upright po -
sition (access valve at the top) when removing liquid refrigerant
for charging. For a cylinder without a dip tube, invert the cylinder,
with the access valve located on the bottom, when adding liquid
refrigerant.
Because Puron (R-410A) refrigerant is a blend, it is strongly rec -
ommended that refrigerant always be removed from the cylinder
as a liquid. Admit liquid refrigerant into the system in the dis -
charge line when breaking the refrigerant system vacuum while
the compressor is OFF. Only add refrigerant (liquid) into the suc -
tion line while the compressor is operating. If adding refrigerant
into the suction line, use a commercial metering/expansion device
at the gage manifold; remove liquid from the cylinder, pass it
through the metering device at the gage set, and then pass it into
the suction line as a vapor. Do not remove Puron (R-410A) refrig -
erant from the cylinder as a vapor.
Refrigerant Charge
Unit panels must be in place when the unit is operating during the
charging procedure. To prepare the unit for charge adjustment.
NO CHARGE
Use standard evacuating techniques. Evacuate the system down to
500 microns and let set for 10 minutes to determine if the system
has a refrigerant leak. If the evacuation level raises to
1100 microns and stabilizes, then the system has moisture in it and
should be dehydrated as GTAC2-5 recommends.
If the system continues to rise above 1100 microns, then the sys -
tem has a leak and should be pressurized and leak tested using ap -
propriate techniques as explained in GTAC2-5. After evacuating
the system, weigh in the specified amount of refrigerant as listed
on the unit's rating plate.
LOW-CHARGE COOLING
Using the Cooling Charging Charts (Fig. 23-30), vary the refriger
-
ant until the conditions of the appropriate chart are met. Note the
charging charts are different from the type normally used. These
charts are based on charging the units to the correct superheat for
the various operating conditions. Accurate pressure gage and tem -
perature sensing devices are required. Connect the pressure gage
to the service port on the suction line. Mount the temperature sens -
ing device on the suction line and insulate it so the outdoor ambi -
ent temperature does not affect the reading. Indoor-air cfm must
be within the normal operating range of the unit.
EXAMPLE:
Model 48TC*D28
Circuit A
Outdoor Temperature . . . . . . . . . . . . . . . . . . . . . . . . . .85°F (29°C)
Suction Pressure . . . . . . . . . . . . . . . . . . . . . . . . 125 psig (860 kPa)
Suction Temperature should be . . . . . . . . . . . . . . . . . .63°F (17°C)
Circuit B
Outdoor Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85° (29°)
Suction Pressure . . . . . . . . . . . . . . . . . . . . . . . . 120 psig (830 kPa)
Suction Temperature should be . . . . . . . . . . . . . . . . . .58°F (14°C)
Using the Cooling Charging Charts
Take the outdoor ambient temperature and read the suction
pressure gage. Refer to the chart to determine what the suction
temperature should be. If the suction temperature is high, add
refrigerant.
If the suction temperature is low, carefully recover some of the
charge. Recheck the suction pressure as the charge is adjusted.
Select the appropriate unit charging chart from Fig. 23-30.
Note the outdoor ambient temperature and read the suction pres -
sure gage. Refer to the chart to determine what the suction tem -
perature should be. If the suction temperature is high, add refriger -
ant. If the suction temperature is low, carefully recover some of the
charge. Recheck the suction pressure as the charge is adjusted.
For 17-28 sizes, perform this procedure once for Circuit A (using
the Circuit A chart) and once for Circuit B (using the Circuit B
chart).
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in damage to
components.
The compressor is in a R-410A refrigerant system and uses a
polyolester (POE) oil. This oil is extremely hygroscopic,
meaning it absorbs water readily. POE oils can absorb
15 times as much water as other oils designed for HCFC and
CFC refrigerants. Avoid exposure of the oil to the atmosphere.
SIZE DESIGNATION NOMINAL TON REFERENCE
17 15
20 17.5
24 20
28 25