10
System Startup
Final Charge Adjustment
(Non-Matching Systems—Cooling Operation)
I
NDOOR
C
OIL
WITH
E
XPANSION
V
ALVE
:
At stabilized cooling conditions and with an outdoor tem-
perature of 60°F or higher, the subcooling at the outdoor
unit liquid line service valve should be subcooling 9 - 15°.
Add or remove charge as required.
I
NDOOR
C
OIL
WITH
O
RIFICE
OR
C
AP
T
UBE
For a proper superheat reading, measure the refrigerant
pressure and temperature at the outdoor unit vapor line
service valve. The superheat should be within 3°F of that
shown on the
Desired Superheat vs Outdoor Temperature
Chart
. If the superheat is higher, add charge. If the
superheat is lower, remove charge.
EXAMPLE
: The low side pressure is 84 psi. The low side
temperature is 80°F. The outdoor temperature is 95°F.
The indoor temperature is 85°F. By referring to a pressure
temperature chart, you will see that 84 psi equals a
saturated temperature of 50°F. The superheat is 80 - 50 =
30°F. The chart shows a superheat of 20°F is ideal for
these conditions. Since our superheat is 30 - 20 = 10°F
higher than ideal, charge must be added.
If the system is performing properly, reinstall the service
port caps and the valve bonnets. With the valve opened,
the valve bonnet is the primary seal against refrigerant
leaks. Apply two drops of clean oil to the cap threads,
allowing the oil to run down to the inner cap seal surface.
Close caps finger-tight. Then tighten cap an additional two
to three hex flats.
NOTE:
Subsequent opening and
replacement of the cap will require only 1/2 to 1 hex flat.
See the table below for the torque required for an effective
seal on the valve bonnet (1/6 turn past finger tight).
Tubing Size
Torque (Foot-Pounds)
3/8
10
1/2, 5/8, 3/4
14
7/8, 1 1/8
16
After closing the valve bonnet, perform a final refrigerant
leak test on the valves and sweat connections. Return the
room thermostat to the desired settings.
4
50
60
70
80
90
100
110
120
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
SUP
E
RHE
AT
@
O
.D.
UN
IT
OUTDOOR TEMPERATURE
DESIRED SUPERHEAT vs OUTDOOR TEMPERATURE
90° F
Ind
oor
70
° F
In
do
or
75
° F
In
do
or
80°
F In
do
or
85°
F In
do
or
