Carrier 38VMH Series - Step 4 - Pressure and Vacuum Test System; Step 5 - Adjust Refrigerant Charge; Step 6 - Complete Electrical Connections

8
Step 4 — Pressure and Vacuum Test
System —
After completing the refrigerant piping, perform
the following pressure test:
1. Connect nitrogen canister to the system through the high-
pressure gas side valve from the meter connector.
2. Apply nitrogen pressure gradually to 500 psig.
3. If rapid pressure decrease is apparent; locate and repair
the leak, and pressurize the system again.
4. Repeat Steps 1-3 until the system remains at 500 psig for
24 hours.
After completing the pressure test, perform the following
vacuum test:
1. Relieve the system of the nitrogen gas.
2. Connect a vacuum pump capable of at least 85 cfm to the
system.
3. Vacuum the system to 500 microns or lower, and check
for rapid pressure change.
4. Repeat Steps 1-3 until the system remains at 500 microns
or lower for one hour.
When finished, replace the vacuum pump with the R-410A
refrigeration canister.
Step 5 — Adjust Refrigerant Charge —
Calculate the amount of refrigerant (R-410A) to add using
Table 8 and Fig. 13.
Table 8 — Refrigerant to Add Using Liquid Pipe
Size
All service valves on the outdoor units should remain fully
closed.
R-410A refrigerant should be added (in liquid state) at the
liquid line service port on the header unit.
If the total calculated amount of refrigerant can be added to the
system, the charging process is finished.
If the total calculated amount of refrigerant cannot be added to
the system, close the valve on the refrigerant bottle, move the
charging house from the liquid line service port to the suction
line service port.
Open the suction and liquid service valves on the header unit
and start the system in cooling mode.
Slowly open the valve on the refrigerant bottle and carefully re-
lease liquid refrigerant into the suction service port.
If the total calculated charge amount is added completely to the
system, the charging process is finished.
Step 6 — Complete Electrical Connections —
See Fig. 14 for a diagram of the unit’s internal power and
control wiring.
PIPE SIZE ON LIQUID SIDE
(in.)
REFRIGERANT TO BE
ADDED PER FOOT (lb/ft)
1
/
4
0.015
3
/
8
0.040
1
/
2
0.080
5
/
8
0.120
3
/
4
0.181
7
/
8
0.255
WARNING
Electrical shock can cause personal injury and death.
Disconnect power supply before making wiring
connections. There may be more than one disconnect
switch. Tag all disconnect locations to alert others not to
restore power until work is completed.
WARNING
All units must be wired strictly in accordance with the
wiring diagram furnished with the unit. Any wiring
different from the wiring diagram could result in personal
injury and property damage.
CAUTION
Any original factory wiring that requires replacement must
be replaced with wiring material having a temperature
rating of at least 105C.
Ensure supply voltage to the unit, as indicated on the serial
plate, is not more than 10% over the rated voltage or 10%
under the rated voltage.
Failure to follow these recommendations may result in
equipment damage.
Fig. 13 — Calculating the Amount of Refrigerant
to Add
* R = Amount of refrigerant to add.
R*=
Total length (ft)
of liquid piping
Size at
ဨ
7/8 in.
x 0.225 +
(lb/ft)
Total length (ft)
of liquid piping
Size at
ဨ
3/4 in.
x 0.181 +
(lb/ft)
Total length (ft)
of liquid piping
Size at
ဨ
5/8 in.
x 0.120 +
(lb/ft)
Total length (ft)
of liquid piping
Size at
ဨ
1/2 in.
x 0.080 +
(lb/ft)
Total length (ft)
of liquid piping
Size at
ဨ
3/8 in.
x 0.040 +
(lb/ft)
Total length (ft)
of liquid piping
Size at
ဨ
1/4 in.
x 0.015 +
(lb/ft)
IDU Model
40VMF012~036A--3
40VMM012~036A--3
Others
Charged amount per unit (lbs.)
1.10
1.10
0
+
x 0.22 (lbs/item)
Y-joints or headers
number in liquid side