4TWL6036A-SF-1F-EN
7
Subcooling Charging in Cooling between 55° F and 120°
OD Ambient
Trane has always recommended installing Trane
approved matched indoor and outdoor systems.
The benefits of installing approved indoor and outdoor
split systems are maximum efficiency, optimum
performance and the best overall reliability.
The following charging methods are therefore
prescribed for matched systems with indoor TXVs/
EEVs.
1. Subcooling (in the cooling mode) is the only
recommended method of charging above 55°
ambient temperatures.
2. For best results — the indoor temperature should
be kept between 70° to 80° F. Add system heat if
needed.
3. At startup, or whenever charge is removed or
added, the system must be operated for a minimum
of (20) minutes to stabilize before accurate
measurements can be made.
4. Measure Liquid Line Temperature and Refrigerant
Pressure at service valves.
5. Determine total refrigerant line length, and height
(lift) if indoor section is above the condenser.
6. Determine the Design Subcooling Charging
Temperature from the unit nameplate.
7. Locate this value in the appropriate column of the
Subcooling Charging Table. Locate your liquid line
temperature in the left column of the table, and the
intersecting liquid line pressure under your
nameplate subcool value column. Add refrigerant
to raise the pressure to match the table, or remove
refrigerant to lower the pressure. Again, wait (20)
minutes for the system conditions to stabilize
before adjusting charge again.
8. When system is correctly charged, you can refer to
System Pressure Curves to verify typical
performance.
Subcool Charging Correction
Charts
50
4°
40
30
25
Use Design Subcooling
15
1°
10
0
20
30
40
50
60
70
80
90
100
110
120
130
140
150
Add 1°
Add 2°
R
E
F
R
IG
E
R
A
N
T
L
IN
E
L
IF
T
(
F
T
)
SUBCOOL CHARGING CHART CORRECTIONS TABLE (FOR LINE LENGTH AND RISE)
TOTAL REFRIGERANT LINE LENGTH (FT) - [ includes lift ]
Add 1°
Weigh-In Method for Charging
Weigh-In Method can be used for the initial installation,
or anytime a system charge is being replaced. Weigh-In
Method can also be used when power is not available
to the equipment site or operating conditions (indoor/
outdoor temperatures) are not in range to verify with
the subcooling charging method.
Calculating Charge Using the Weigh-In Method
STEP 1 -
Measure in feet the
distance between the outdoor unit
and the indoor unit. (Include the
entire length of the line from the
service valve to the IDU.) Subtract
10 ft from this entire length and
record on line 1.
1. Total
Line Length
(ft) – 10 ft
STEP 2 -
Enter the charge multiplier
(0.6 oz/ft). Each linear foot of
interconnecting tubing requires the
addition of 0.6 oz of refrigerant.
2. Charge
multiplier
x 0.6 oz
STEP 3 -
Multiply the total length of
refrigerant tubing (Line 1) times the
value on Step 2. Record the result on
Line 3 of the Worksheet.
3. Step 1 x
Step 2
=
_______-
____
STEP 4 -
This is the amount of
refrigerant to weigh-in prior to
opening the service valves.
4.
Refrigerant
(oz)
=
_______-
___oz
