38MURA: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
15
Step 7 - Evacuate Coil And Tubing System
Refrigerant tubes and the indoor coil should be evacuated using the
recommended 500 microns deep vacuum method. The alternate triple
evacuation method may be used if the procedure outlined below is
followed.
NOTE: Always break a vacuum with dry nitrogen.
Using Vacuum Pump
1. Completely tighten flare nuts A, B, C, D. Connect the manifold gage
charge hose to a charge port of the low side service valve (see Fig. 24).
2. Connect the charge hose to vacuum pump.
3. Fully open the low side of manifold gage (see Fig. 25).
4. Start the vacuum pump.
5. Evacuate using either the deep vacuum or 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 25 ft.
(8 m) of line length. For refrigerant lines longer than 25 ft. (8 m), add
refrigerant, up to the allowable length.
8. Disconnect the charge hose from the charge connection of the low side
service valve.
9. Fully open service valves B and A.
10. Securely tighten the service valve caps.
Fig. 24 — Service Valve
Fig. 25 — Manifold
Evacuation
Evacuation of the system will remove air or nitrogen (non-condensables) as
well as moisture. A proper vacuum will assure a tight, dry system before
charging with refrigerant. The two methods used to evacuate a system are the
deep vacuum method and the triple vacuum method.
Deep Vacuum Method
The deep vacuum method requires a vacuum pump capable of pulling a vacuum
of 500 microns and a vacuum gauge 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 moisture (see Figure 26).
Fig. 26 — Deep Vacuum Graph
Triple Evacuation Method
The triple evacuation method should be used when vacuum pump
is not capable of pumping down to 500 microns and system does not
contain any liquid water. Refer to Fig. 27 and proceed as follows:
1. Attach refrigeration gauges and evacuate 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 flow nitrogen
until system pressure is 2 psig.
4. Close service valve and allow system to stand for 1 hour. During this
time, dry nitrogen will be able to diffuse throughout the system
absorbing moisture.
5. Repeat this procedure as indicated in Fig. 27. System is now free of any
contaminants and water vapor.
Fig. 27 — Triple Evacuation Method
Final Tubing Check
Check to be certain factory tubing on both the 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 the 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 UnitRefrigerant
Service Valve
High side valve
Charge hose
Charge hose
Vacuum
01234567
1000
1500
LEAK IN
SYSTEM
SYSTEM TIGHT
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
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