System Evacuation And Charging; System Vacuum And Charge; Using Vacuum Pump; Deep Vacuum Method - Carrier 38MAQB12-1 Service Manual

SYSTEM EVACUATION AND CHARGING

CAUTION
!
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.
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.

System Vacuum and Charge

Using Vacuum Pump

1 Completely tighten all flare nuts and connect manifold gage
charge hose to a charge port of the low side service valve
(see Fig. 13).
2 Connect the charge hose to the vacuum pump.
3 Fully open the low side of the manifold gage (see Fig. 14).
4 Start the vacuum pump.
5 Evacuate using the triple evacuation method.
6 After evacuation is complete, fully close the low side of
manifold gage and stop the vacuum pump operation.
7 The factory charge contained in the outdoor unit is good for
up to 25ft. (8 m) of line length.
8 Disconnect the charge hose from the charge connection of
the low side service valve.
9 Securely tighten the service valves caps.
Refrigerant
Outdoor Unit
A
B
Service Valve
Fig. 13 – Service Valve
Manifold Gage
500 microns
Low side valve
Charge hose
Low side valve
Fig. 14 – Manifold
Indoor Unit
Low Side C
D
High Side
High side valve
Charge hose
Vacuum pump

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 the vacuum depth. The deep vacuum method
is the most positive way of assuring a system is free of air and
liquid water (see Fig. 15).
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0 1 2 3
MINUTES
Fig. 15 – Deep Vacuum Graph
Triple Evacuation Method
The triple evacuation method should be used. Refer to Fig. 16 and
proceed as follows:
1 Pump system down to 500 MICRONS of mercury and
allow the pump to continue operating for an additional 15
minutes. Unit must maintain 500 microns or less for 30
minutes or more to ensure a dry system.
2 Close the service valves and shut off the vacuum pump.
3 Connect a nitrogen cylinder and regulator to system and
open until the system pressure is 2 psig.
4 Close the service valve and allow the system to stand for 10
minutes. During this time, dry nitrogen will be able to
diffuse throughout the system absorbing moisture.
5 Repeat this procedure as indicated in Fig. 16. The system
will then be free of any contaminants and water vapor.
EVACUATE
BREAK VACUUM WITH DRY NITROGEN
WAIT
EVACUATE
BREAK VACUUM WITH DRY NITROGEN
WAIT
EVACUATE
CHECK FOR TIGHT, DRY SYSTEM
(IF IT HOLDS DEEP VACUUM)
RELEASE CHARGE INTO SYSTEM
Fig. 16 – 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.
19
LEAK IN
SYSTEM
VACUUM TIGHT
TOO WET
TIGHT
DRY SYSTEM
4 5 6 7