Carrier 38MGQ Series, Installation Instructions Manual

Page: 16 / 18

16
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. 19).
500
MINUTES
0 1 2 3 4 5 6 7
1000
1500
LEAK IN
SYSTEM
VACUUM TIGHT
TOO WET
TIGHT
DRY SYSTEM
2000
MICRONS
2500
3000
3500
4000
4500
5000
A95424
Fig. 19
-
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. 20 and proceed as follows:
1. Pump system down to 28 in. of mercury and allow the
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.
During this time, dry nitrogen will be able to diffuse
throughout the system absorbing moisture.
5. Repeat this procedure as indicated in Fig. 20. System will
then be free of any contaminants and water vapor.
CHECK FOR TIGHT, DRY SYSTEM
(IF IT HOLDS DEEP VACUUM)
EVACUATE
BREAK VACUUM WITH DRY NITROGEN
WAIT
EVACUATE
RELEASE CHARGE INTO SYSTEM
BREAK VACUUM WITH DRY NITROGEN
EVACUATE
WAIT
A95425
Fig. 20
-
Triple Evacuation Method
Final Tubing Check
IMPORTANT
: Check to be certain the 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.