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38MGRBQ: 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.
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. 18).
2. Connect charge hose to vacuum pump.
3. Fully open the low side of manifold gage (see Fig. 19).
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.
8. Disconnect the charge hose from charge connection of the low side
service valve.
9. Securely tighten caps of service valves.
Outdoor Unit
A
B
Service Valve
Fig. 18 — Service Valve
Manifold Gage
500 microns
Low side valve
Charge hose
Low side valve
Fig. 19 — Manifold
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Indoor Unit
Refrigerant
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 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.
20).
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
1
Fig. 20 — Deep Vacuum Graph
Triple Evacuation Method
The triple evacuation method should be used. Refer to Fig. 21 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.
EVACUATE TO 1500 MICRONS
BREAK VACUUM WITH DRY NITROGEN TO 2 PSIG
EVACUATE TO 1000 MICRONS
BREAK VACUUM WITH DRY NITROGEN TO 2 PSIG
EVACUATE TO 500 MICRONS MINIMUM (HOLD FOR 30 MINUTES)
CHECK FOR TIGHT, DRY SYSTEM
(IF IT HOLDS DEEP VACUUM)
RELEASE CHARGE INTO SYSTEM BY OPENING VALVES COMPLETELY
Fig. 21 — 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
2
3
4
5
6
7
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