Suction Lines - Trane BCHE Installation, Operation And Maintenance Manual

only required for constant-volume applications when
dehumidification is a concern.
In split systems with micro-channel heat exchanger
condensers (MCHE), solenoid valves isolate the refrigerant
from the evaporator during the off cycles. Trim solenoids
cannot be used with MCHE.
Note: Trane condensing units with MCHE no longer employ
pump-down, but isolation solenoids are required.
The suggested solenoid uses a 120-volt service and
requires code-compliant wiring to the condensing
unit.
Moisture-indicating sight glass
Be sure to install one moisture-indicating sight glass in the
main liquid line. The only value of the sight glass is its
moisture indication ability. Use actual measurements of
temperature and pressure—not the sight glass—to
determine subcooling and whether the system is properly
charged. The moisture indicator/sight glass must be sized
Figure 49. Type F refrigerant coil with packed elbow
Panel
Coil
Ball shut-off valves:
Adding manual, ball-type shutoff valves upstream and
downstream of the filter simplifies replacement of the filter
core.

Suction Lines

Line sizing
Proper line sizing is required to guarantee the oil returns to
the compressor throughout the system's operating
envelope. At the same time, the line must be sized so that
the pressure drop does not excessively affect capacity or
efficiency. To accomplish both objectives, it may be
necessary to use two different line diameters: one for the
horizontal run and for the vertical drops, and another for the
vertical lifts (risers).
Routing
To prevent residual or condensed refrigerant from "free-
flowing" toward the compressor during the off cycle, install
the suction line so it slopes by ¼ inch to 1 inch per 10 feet
of run toward the evaporator.
BCX-SVX002A-EN
Perforated plate
(packed elbow)
Venturi type
distributor
to match the size of the liquid line at the thermal expansion
valve.
Valve Damage!
Failure to protect the valve from high temperatures
could result in damage to internal components.
Disassemble the thermal expansion valve before
completing the brazing connections. If necessary,
wrap the valve in a cool, wet cloth while brazing.
Thermal expansion valve:
The expansion valve is the throttling device that meters the
refrigerant into the evaporator coil. Metering too much
refrigerant floods the compressor; metering too little
elevates the compressor temperature. Choosing the
correct size and type of expansion valve is critical to assure
it will correctly meter refrigerant into the evaporator coil
throughout the entire operating envelope of the system.
Cut here
for piping
When the application includes a suction riser, oil must be
forced to travel the height of the riser. Riser traps are
unnecessary in the suction line. They will add pressure
drop. Double risers must not be used. They not only add
pressure drop, but can hold great amounts of oil - oil better
used in the compressor.
If a suction riser is properly sized, oil will return to the
compressor regardless of whether a trap is present. If a
suction riser is oversized, adding a trap will not restore
proper oil entrainment.
Avoid Underground Refrigerant Lines
Refrigerant condensation during the off cycle, installation
debris inside the line (including condensed ambient
moisture), service access, and abrasion/corrosion can
quickly impair reliability.
Insulation
Any heat that transfers from the surrounding air to the
cooler suction lines increases the load on the condenser
(reducing the system's air-conditioning capacity) and
promotes condensate formation. After operating the
Piping and Connections
NOTICE
57