Carrier 38MGRQ48E 3 Series - SYSTEM EVACUATION AND CHARGING; Vacuuming and Charging Procedures; Deep and Triple Evacuation Methods

38MGR-04SM Specifications subject to change without notice. 25
SYSTEM EVACUATION AND CHARGING
Refrigerant tubes and indoor coil should be evacuated using the
recommended deep vacuum method of 500 microns. The alternate
triple evacuation method may be used if the following procedure is
followed. Always break a vacuum with dry nitrogen.
NOTE: All units (except the 18,000 BTU model) have a
Master Suction and Liquid Line Service Valve.
System Vacuum and Charge
Using Vacuum Pump
1. Completely tighten the flare nuts (A, B, C, D, E). Fully open all
circuits service valves. Connect the manifold gage charge hose to
the charge port of the low side Master service valve to evacuate all
circuits at the same time (see Fig. 23).
2. Connect charge hose to vacuum pump.
3. Fully open the low side of manifold gage (see Fig. 24).
4. Start vacuum pump
5. Evacuate using the triple evacuation method.
6. After evacuation is complete, fully close the low side of manifold
gage and stop operation of vacuum pump.
7. The factory charge contained in the outdoor unit is good for up
to 25ft. (8 m) of line length. For refrigerant lines longer than
25ft. (8 m), add refrigerant as specified in “Additional Charge
Table Per Zone” on page 24.
8. Disconnect charge hose from charge connection of the low side
service valve.
9. Securely tighten caps of service valves.
Fig. 23 — Service Valve
Fig. 24 — Manifold
Deep Vacuum Method
The deep vacuum method requires a vacuum pump capable of pulling
a vacuum of 500 microns and a vacuum gage capable of accurately
measuring this vacuum depth. The deep vacuum method is the most
positive way of assuring a system is free of air and liquid water (see
Fig. 25).
Fig. 25 — Deep Vacuum Graph
Triple Evacuation Method
The triple evacuation method should be used. Refer to Fig. 26 and
proceed as follows:
1. Pump the system down to 1500 microns and allow the pump to
continue operating for an additional 15 minutes.
2. Close the service valves and shut off the vacuum pump.
3. Connect a dry nitrogen cylinder and regulator to the system and
break vacuum until the system reaches 2 psig.
4. Close the service valve and allow the system to stand for 1 hour.
During this time, the dry nitrogen can diffuse throughout the system
absorbing moisture.
5. Pump the system down to 1000 microns.
6. Break the vacuum with dry nitrogen (2 psig).
7. Pump the system down to 500 microns.
8. Perform the hold test for 30 minutes.
Fig. 26 — Triple Evacuation Method
Final Tubing Check
IMPORTANT: Check to be certain factory tubing on both
indoor and outdoor unit has not shifted during shipment.
Ensure tubes are not rubbing against each other or any sheet
metal. Pay close attention to feeder tubes, making sure wire
ties on feeder tubes are secure and tight.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage
or improper operation.
Never use the system compressor as a vacuum pump.
CAUTION
Outdoor Unit
Indoor Uni
t
Refrigerant
Service Valve
Low Side
High Side
A
B
C
D
Manifold Gage
500 microns
Low side valve
High side valve
Charge hose
Charge hose
Vacuum
pump
Low side valve
500
MINUTES
01234 567
1000
1500
LEAK IN
SYSTEM
VACUUM TIGH
T
TOO WET
TIGHT
DRY SYSTEM
2000
MICRONS
2500
3000
3500
4000
4500
5000
CHECK FOR TIGHT, DRY SYSTEM
(IF IT HOLDS DEEP VACUUM)
EVACUATE TO 1500 MICRONS
EVACUATE TO 500 MICRONS MINIMUM (HOLD FOR 30 MINUTES)
RELEASE
CHARGE INTO SYSTEM BY O
PENING VALVES COMPLETELY
BREAK VACUUM WITH DRY NITROGEN TO 2 PSIG
EVACUATE TO 1000 MICRONS
BREAK VACUUM WITH DRY NITROGEN TO 2 PSIG