42
IM 738-2
Mechanical Installation:
RFS/RCS Permanent Split Systems
Charging the System
RCS units are leak tested at the factory and shipped with a
nitrogen holding charge. If the holding charge has been lost
due to shipping damage, then contact the factory for
authorization and advice for repairing the leak and evacuating
the system.
1
After all refrigerant piping is complete and the system is
evacuated, it can be charged as described in the paragraphs
following. Connect the refrigerant drum to the gauge port
on the liquid shutoff valve and purge the charging line
between the refrigerant cylinder and the valve. Then open
the valve to the midposition.
2
If the system is under a vacuum, stand the refrigerant drum
with the connection up, open the drum, and break the
vacuum with refrigerant gas.
3
With a system gas pressure higher than the equivalent of a
freezing temperature, invert the charging cylinder and
elevate the drum above the condenser. With the drum in
this position and the valves open, liquid refrigerant flows
into the condenser. Approximately 75% of the total
requirement estimated for the unit can be charged in this
manner.
4
Refrigerant charging with Zeotropes—R-407C is a
zeotropic mixture (see “Refrigerant Leaks” on page 117).
During initial charging or “topping” off a system, it is
important to remove the refrigerant from the charging
cylinder in the liquid phase. Many of the cylinders for the
newer refrigerants use a dip tube so that in the upright
position liquid is drawn from the cylinder. DO NOT vapor
charge out of a cylinder unless the entire cylinder is to be
charged into the system. Refer to charging instructions
provided by the refrigerant manufacturer.
5
After 75% of the required charge enters the condenser,
reconnect the refrigerant drum and charging line to the
suction side of the system. Again, purge the connecting
line, stand the drum with the connection side up, and place
the service valve in the open position.
Note:
Stamp the total operating charge per circuit on the unit
nameplate for future reference.
Take special care to add refrigerant slowly enough to the
suction to prevent damage when first adding charge to the
suction. Adjust the charging tank hand valve extremely slow
Table 18: Pressure-vacuum equivalents
Absolute pressure above zero
Vacuum below 1 atmosphere
Approximate
fraction of
1 atmosphere
Boiling point
of H2O at each
pressure (
o
F)
Microns
PSIA
Mercury (mm)
Mercury (in.)
0
0
760.00
29.921
—
—
50
0.001
759.95
29,920
1/15,200
–50
100
0.002
759.90
29.920
1/7,600
–40
150
0.003
759.85
29.920
1/5,100
–33
200
0.004
759.80
29.910
1/3,800
–28
300
0.006
759.70
29.910
1/2,500
–21
500
0.009
759.50
29.900
1/1,520
–12
1,000
0.019
759.00
29.880
1/760
1
2000
0.039
758.00
29.840
1/380
15
4,000
0.078
756.00
29.760
1/189
29
6000
0.117
754.00
29.690
1/127
39
8,000
0.156
752.00
29.600
1/95
46
10,000
0.193
750.00
29.530
1/76
52
15,000
0.290
745.00
29.330
1/50
63
20,000
0.387
740.00
29.130
1/38
72
30,000
0.580
730.00
28.740
1/25
84
50,000
0.967
710.00
27.950
1/15
101
100,000
1.930
660.00
25.980
2/15
125
200,000
3.870
560.00
22.050
1/4
152
500,000
9.670
260.00
10.240
2/3
192
760,000
14.697
0
0
1 Atmosphere
212
CAUTION
Adding refrigerant to the suction must always be done by
trained service personnel that are experienced with the risks
associated with liquid-related damage to the compressor.
Summary of Contents for RDT-135c
Page 131: ...IM 738 2 129...
