SS-APG008H-EN
11
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Rise at least 1 ft (30 cm) from the common low point to
prevent any off-cycle condensed refrigerant in the coil
from attempting to flow to the compressor.
Double risers
MUST NOT
be installed. All 6 – 25 ton TTA
and TWA units unload such that a single gas line size,
preselected in the Component Selection tables found
in
, provide sufficient velocity to push
entrained oil up the permissible riser height.
Note:
If a gas riser is properly sized, oil will return to the
compressor regardless of whether a trap is present.
If a gas riser is oversized, adding a trap will not
restore proper oil entrainment.
Figure 5.
Gas-line arrangement at the outlet of a field-
supplied indoor coil
DETINT (Double Elbow
That Is Not a Trap)
DETINT
The riser DETINT (Double-Elbow That Is Not a Trap) does
not retain oil during unit operation. When the unit is off, the
DETINT prevents liquid oil or refrigerant from draining in
either direction. It also allows sub-cooled oil and liquid
refrigerant to drain past the TXV bulb. This promotes stable
TXV operation.
Avoid Underground Refrigerant Lines
Underground lines create risk due to refrigerant
condensation during the off cycle, installation debris inside
the line (including condensed ambient moisture), service
access, and abrasion/corrosion. These hazards can quickly
impair reliability.
Insulation
Any heat that transfers from the surrounding air to the
cooler gas lines increases the load on the condenser
(reducing the system’s air-conditioning capacity) and
promotes condensate formation. After operating the
system and testing all fittings and joints to verify that the
system is leak-free, insulate the gas lines per local code
requirements. This will prevent heat gain and unwanted
condensation.
Components
Adding a gas line filter is unnecessary—provided that good
refrigerant practices (including nitrogen sweeping during
brazing and proper system evacuation) are followed.
Access Port
Providing an access port in the gas line at the coil permits
the servicer to check refrigerant pressure and determine
superheat at the evaporator/indoor coil. This port is usually
a Schraeder valve with a core. See Note 1 in
and
for more details.
