AAON CF Series - Figure 12 - Oil Return Line

41
When installing vertical hot gas bypass lines,
an oil drip line must be provided at the lowest
point in the system. The oil drip line must be
vertical, its diameter must be the same as the
diameter of the riser, and a maximum of
25.4 cm (10”) long. Install a sight glass in the
oil drip line for observation. Run an oil return
line, using 3.2 mm (1/8 inch) capillary tube,
3 meters (10 feet) in length, from the hot gas
bypass line oil drip line to the suction line.
Connect the oil return line below the sight
glass and 1 inch above the bottom of the oil
drip line.
Figure 12 - Oil Return Line
HGB valves are adjustable. Factory HGB
valve settings will be sufficient for most
applications, but may require slight
adjustments for some applications, including
some make up air applications.
Insulate the entire length of the HGB line
with a minimum 2.5 cm (1 inch) thick
Armaflex insulation.
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return,
and minimize refrigerant charge.
Maintain velocities below a maximum of
17.8 m/s (3,500 fpm). A general minimum
velocity guideline to use is approximately
10.2 m/s (2,000 fpm).
Hot Gas Reheat
The AAON modulating hot gas reheat system
diverts hot discharge gas from the condenser
to the air handling unit through the hot gas
line. Field piping between the condensing
unit and the air handler is required.
The line delivers the hot discharge gas to the
reheat coil and/or the hot gas bypass valve, so
it is sized as a discharge line.
Discharge lines must be sized to ensure
adequate velocity of refrigerant to ensure oil
return, avoid excessive noise associated with
velocities that are too high, and to minimize
efficiency losses associated with friction.
Pitch the hot gas line in the direction of flow
for oil return.
When installing vertical hot gas reheat lines,
an oil drip line must be provided at the lowest
point in the system. The oil drip line must be
vertical, its diameter must be the same as the
diameter of the riser, and a maximum of
25.4 cm (10”) long. Install a sight glass in the
oil drip line for observation. Run an oil return
line, using 3.2 mm (1/8 inch) capillary tube,
3 meters (10 feet) in length, from the hot gas
reheat line oil drip line to the suction line.
Connect the oil return line below the sight
glass and 1 inch above the bottom of the oil
drip line. (See Oil Return Line Figure 12)
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation.
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
17.8 m/s (3,500 fpm). A general minimum
velocity guideline to use is approximately
10.2 m/s (2,000 fpm).