Installing A Piston - Johnson Controls XAF Series Installation Manual

NOTICE
To prevent moisture and contaminates from entering
the system, the coil should not be open to atmosphere
for extended periods of time. If the coil cannot be
brazed into the refrigeration system during a routine
installation period, the ends should be temporarily
closed or plugged. For a short term delay, use
masking tape over the ends of the copper tubing to
close the tube from the air. For a longer term delay,
use plugs or caps. There is no need to purge the coil if
this procedure is followed.

Installing a piston

About this task:
WARNING
Failure to install Schrader valve core in the vapor line
equalizer connection port for piston applications could
result in total refrigerant loss of the system.
Follow these steps to install a Schrader valve core and
piston on XAF, XAH, or XAU coils.
1. When the holding charge is completely discharged,
remove the black plastic cap from the equalizer
connection port on the vertical part of the vapor
line.
2. Adjust the distributor position to allow the
preformed liquid line assembly to correctly line up
with the hole in the tubing access panel. Raise the
distributor body approximately 2 in. toward the top
of the coil or what would be the top of the coil if
the coil was in the upflow position, and adjust as
necessary. See Figure 10.
3. Install the Schrader valve core supplied with the
outdoor unit into the equalizer fitting connection
port using a valve core tool.
4. Loosen and remove the liquid line connection nut
and the sealing disc from the distributor assembly.
Note: The fitting has right-hand threads.
5. Slide the nut over the liquid line that is being
installed and discard the seal disc.
6. Install the required size piston into the distributor.
Refer to the Tabular Data Sheet for information on
the specific piston size and indoor coil matchup.
See Figure 11.
7. Verify that the PTFE washer is still in place in the
distributor opening. See Figure 11.
Installation Manual: XAF, XAH, and XAU Series - Full Cased and Uncased Coils for Cooling and Heat Pumps
Figure 10: Recommended distributor adjustment
Figure 11: Piston installation
Do not over torque. Do not use slip joint pliers. This
will distort the aluminum distributor and the brass
fitting (potentially causing leaks).
8. When the piston is installed, install the liquid line to
the top of the piston or distributor assembly. Hand
tighten and turn an additional 1/4 turn to seal.
9. Replace the black plastic cap on the unused
equalizer fitting connection port.
10. When the refrigeration piping is installed, leak test
the system.
Johnson Controls Ducted Systems
CAUTION
Note: Do not overtighten the fittings.
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