Lennox XP17-024-230-01 Installation And Service Procedure page 75

Figure 45. Deep Vacuum Gauge Response and
System Conditions
Triple Evacuation Method
The triple evacuation method should only be used when
system does not contain any water in liquid form and
vacuum pump is only capable of pulling down to 28 inches
of mercury (711mm Hg). Refer to figure 46 and proceed as
follows:
Trip Evacuation Sequence
EVACUATE
BREAK VACUUM WITH DRY NITROGEN
EVACUATE
BREAK VACUUM WITH DRY NITROGEN
CHECK FOR TIGHT, DRY SYSTEM (IF IT HOLDS DEEP VACUUM)
RELEASE CHARGE TO SYSTEM
Figure 46. Trip Evacuation Sequence
XP17
WAIT
WAIT
EVACUATE
1. Pull system down to 28 inches of mercury (711mm Hg)
and allow pump to continue operating for an additional
15 minutes.
2. Close manifold valves or valve at vacuum pump and
shut off vacuum pump.
3. Connect a nitrogen cylinder and regulator to system
and fill with nitrogen until system pressure is 2 psig.
4. Close nitrogen valve and allow system to stand for one
hour. During this time, dry nitrogen will diffuse
throughout the system absorbing moisture.
5. Repeat this procedure as indicated in figure 46.
System will then be free of any airborne containment
and water vapor.
6. After the final evacuate sequence, confirm there are no
leaks in the system. If a leak is found, repeat the entire
process after repair is made.
7. Reconnect the manifold gauge to the vacuum pump,
turn the pump on, and continue to evacuate the line set
and indoor unit until the absolute pressure does not
rise above 500 microns (29.9 inches of mercury) within
a 20*minute period after shutting off the vacuum
pump and closing the manifold gauge valves.
8. Disconnect the manifold hose from the vacuum pump
and connect it to an inverted cylinder of HFC*410A
positioned to deliver liquid refrigerant. Open the
manifold gauge valve 1 to 2 psig in order to release the
vacuum in the line set and indoor unit.
9. Perform the following:
S
Close manifold gauge valves.
S
Shut off HFC*410A cylinder.
S
Slowly open the service valves.
S
Refer to the charging sticker on the unit to
complete the outdoor unit installation.
Page 75