Evaporator Coils; Hot Gas Reheat; Hot Gas Bypass; Refrigerant-To-Water Heat Exchanger - AAON M2 Series Installation Operation & Maintenance

Evaporator Coils

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
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.
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 20 - 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. Connect the hot gas line from the
outdoor unit to
connection of the reheat coil in the air
handling unit.
making solder
the upper stub-out
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 (HGB) 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.

Refrigerant-to-Water Heat Exchanger

Condenser water pump, condenser water
piping, cooling tower, pressure gauges,
strainers and all
waterside piping must be field installed.
CAUTION
WATER-SOURCE HEAT PUMP
APPLICATIONS
Water-source heat pump units using
100% outside air must have electric
preheat if the application has a
potential for heat pump heating
operation with air entering the indoor
coil below 43°F with an entering
water loop temperature of 70°F.
components of the
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