System Evacuation And Charging; System Vacuum And Charge; Deep Vacuum Method; Triple Evacuation Method - Carrier 38GVM Series 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 procedure outlined
below is followed. Always break a vacuum with dry nitrogen.

SYSTEM VACUUM AND CHARGE

Using Vacuum Pump
1. Completely tighten flare nuts A, B, C, D, connect manifold
gage charge hose to a charge port of the low side service
valve. (See Fig. 19.)
2. Connect charge hose to vacuum pump.
3. Fully open the low side of manifold gage. (See Fig. 20)
4. Start vacuum pump
5. Evacuate using either deep vacuum or 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 25 ft. (8 m) of line length. For refrigerant lines longer
than 25 ft (8 m), add 0.1 oz. per foot of extra piping up to
total allowable piping length aS listed in physical data.
8. Disconnect charge hose from charge connection of the low
side service valve.
9. Fully open service valves B and A.
10. Securely tighten caps of service valves.
Refrigerant
Outdoor Unit
A
B
Service Valve
Fig. 19 – Service Valve
Manifold Gage
500 microns
Low side valve
Charge hose
Low side valve
Fig. 20 – Manifold
Indoor Unit
Low Side C
D
High Side
A07360
High side valve
Charge hose
Vacuum pump
A07361

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. 21)
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0 1 2 3
MINUTES
Fig. 21 – Deep Vacuum Graph

Triple Evacuation Method

The triple evacuation method should only be used when vacuum
pump is only capable of pumping down to 28 in. of mercury
vacuum and system does not contain any liquid water.
Refer to Fig. 22 and proceed as follows:
1. Pump system down to 28 in. of mercury and allow pump to
continue operating for an additional 15 minutes.
2. Close service valves and shut off vacuum pump.
3. Connect a nitrogen cylinder and regulator to system and
open until system pressure is 2 psig.
4. Close service valve and allow system to stand for 1 hr. Dur-
ing this time, dry nitrogen will be able to diffuse throughout
the system absorbing moisture.
5. Repeat this procedure as indicated in Fig. 22. 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. 22 – 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.
21
LEAK IN
SYSTEM
VACUUM TIGHT
TOO WET
TIGHT
DRY SYSTEM
4 5 6 7
A95424
A95425