IV. CONNECT REFRIGERANT PIPING
Fan coil units may be connected to the outdoor units using
field-supplied refrigerant grade piping. Refer to Table 3 for
the correct size piping. The length of refrigerant pipe de-
pends on the unit placement and building structure; run pipes
as directly as possible. For piping requirements over 50 ft of
total run, or more than 25 ft of lift, consult the long line ap-
plication guidelines available in the product presale litera-
ture, or contact your local representative.
CAUTION:
DO NOT BURY MORE THAN 36 IN. OF
REFRIGERANT PIPE IN THE GROUND. If any sec-
tion of pipe is buried, there must be a 6-in. vertical rise
to the valve connections on the outdoor unit. If more
than the recommended length is buried, refrigerant may
migrate to the cooler, buried section during extended
periods of unit shutdown, causing refrigerant slugging
and possible compressor damage at start-up.
Use the following instructions to connect piping.
1. Install insulation. Insulate
all
refrigerant lines on heat
pumps 538S and systems to prevent condensation. It is
extremely important that all refrigerant lines and the
AccuRater
t
metering device be insulated on heat pumps.
On 538A cooling only units, the liquid line may be left
uninsulated. Use any acceptable heat resistant closed-
cell foam insulation (minimum
3
⁄
8
-in. wall thickness). When
insulating piping, cap ends and slide insulation over
the piping. Insulation can also be cut and placed over
piping.
2. Run liquid and gas refrigerant piping.
a. Run pipes as directly as possible and avoid any un-
necessary turns and bends.
b. Suspend refrigerant pipes so that the insulation is
not damaged and vibrations are not transmitted to
the structure.
c. Leave slack in the refrigerant pipe between the struc-
ture and the unit to absorb vibrations.
d. Install factory-supplied flare connection and Accu-
Rater metering device in liquid line at the fan coil
unit on 538A and 538B systems (Fig. 9). Make sure
the arrow on the metering device body points
AWAY
FROM
the fan coil unit. Use Table 4 to verify that
the correct piston for your system has been shipped
with the unit.
NOTE:
No AccuRater is required on 538S systems. The 538S
systems have a TXV (thermostatic expansion valve) in the
condensing unit for refrigerant metering and control.
e. On heat pump installations, install factory-supplied
piston in the AccuRater metering device located in
the service valve on the outdoor unit (Fig. 10). Make
sure Teflon seal on the piston faces toward the out-
door unit. Use Table 4 to verify the correct piston for
your system has been shipped with the unit. Refer to
538B installation instructions for more details.
f. Install a liquid line filter drier near the outdoor unit
(538A and 538B). On heat pump systems, a bi-flow
filter drier must be used. DO NOT install a filter drier
in 538S systems.
Fig. 6 — Bracket Mounting
NOTE: Use either point ‘‘A’’ or point ‘‘B’’.
Fig. 7 — Wall Hole Location for Rear Piping
Fig. 8 — Piping Hole
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