29
Evaporator Coil
The air handling unit coils are pressurized.
The copper caps must be punctured to permit
a gradual escape of the pressure prior to
un-sweating those caps. Immediately couple
the tubing to the indoor unit to avoid
exposing the coils to moisture. A properly
sized filter drier is furnished in the condenser.
When making solder connections, make sure
dry nitrogen flows through the lines, when
heating the copper, to prevent oxidization
inside of the copper.
Field piping between
the condensing unit and the air handler is
required. Line sizes must be selected to
meet actual installation conditions, not
simply based on the connection sizes.
Thermal Expansion Valve
Thermal expansion valve bulbs should be
mounted with good thermal contact on a
horizontal section of the suction line close to
the evaporator, but outside the cabinet, and
well insulated. On suction lines less than or
equal to 7/8” OD, mount in the 12 o’clock
position. On suction lines greater than 7/8”
OD, mount in either the 4 o’clock or 8
o’clock position.
Figure 16 - TXV Bulb Position
Hot Gas Reheat
Hot Gas Reheat (HGRH) is available for use
with DX systems that need humidity control.
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. Line
sizes must be selected to meet actual
installation conditions, not simply based
on the connection sizes.
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.
Hot Gas Bypass
Hot Gas Bypass is available for use with DX
systems that may experience low suction
pressure during the operating cycle. This may
be due to varying load conditions associated
with VAV applications or units supplying a
large percentage of outside air. Hot Gas
Bypass is not necessary in units with variable
capacity compressors. The system is
designed to divert refrigerant 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. Line sizes
must be selected to meet actual installation
conditions, not simply based on the
connection sizes.
REFRIGERANT PIPING
Line sizes must be selected to meet
actual installation conditions, not
simply based on the connection sizes
at the condensing unit or air handling
unit.
CAUTION
