AAON V3-E - Manual (Page 31)

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from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load.
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed.
Field piping between the condensing unit
and the evaporator is required.
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass (HGB) line
downward in the direction of refrigerant
flow, toward the evaporator.
When installing hot gas bypass risers, a
drain leg must be provided at the lowest
point in the system. The drain leg must be
vertical, its diameter should be the same as
the diameter of the riser, and it should be 1
foot long. Install a sight glass in the drain
leg for observation. Run an oil drip line,
using 1/8 inch capillary tube, 10 feet in
length, from the drain leg to the suction line.
Connect the oil drip line below the sight
glass and 1 inch above the bottom of the
drain leg. 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 1 inch thick Armaflex
insulation.
Hot Gas Bypass Piping Considerations for
Evaporator below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator.
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return,
and minimize refrigerant charge.
Maintain velocities below a maximum of
4,000 fpm. A general minimum velocity
guideline to use is approximately 1,000 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 should 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 hot gas reheat risers, a drip
leg must be provided at the lowest point in
the system. The drip leg must be vertical, its
diameter should be the same as the diameter
of the riser, and it should be 1 foot long. Run
a drip line, using 1/8 inch capillary tube, 10
feet in length, from the drip leg to the
suction line. Connect the drip line a
minimum of 1-inch above the bottom of the
drain leg.
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation.