AAON V3-E - Manual (Page 25)

25
Duct Connection
Attach duct to flanges provided on the unit.
The installer is responsible for sealing ducts
to the flanges to prevent water leaks.
Refer to Figure 6 and Figure 7 for duct
connection locations. Ductwork should be
sized in accordance with the ASHRAE
Handbook. Ductwork should be installed in
accordance with NFPA Standard 90A.
When attaching duct to the unit, use a
flexible/compressible material rated for duct
connections. A three inch flexible connector
for both return and supply duct connections
is recommended.
Condensate Drain Piping
Unit may be equipped with more than one
condensate drain pan connection. A p-trap
and drain line must be installed on at least
one section’s drain connection, with the p-
trap not to exceed 6” from the drain
connection. The lines should be the same
pipe size or larger than the drain connection,
include a p-trap, and pitch downward toward
drain. An air break should be used with long
runs of condensate lines.
Draw-through cooling coils will have a
negative static pressure in the drain pan area.
This will cause an un-trapped drain to back
up due to air being pulled up through the
condensate drain piping.
Condensate drain trapping and piping should
conform to all applicable governing codes.
Note: The drain pan connection(s) is a 1”
MPT fitting.
Figure 8 - Drain Trap
The X dimension on the draw-through trap
should be at least equal to the absolute value
of the negative static pressure in the drain
pan plus one inch. To calculate the static
pressure at the drain pan add the pressure
drops of all components upstream of the
drain pan, including the cooling coil, and
add the return duct static pressure. Include
the dirt allowance pressure drop for the
filters to account for the worst-case scenario.
The height from top of the bottom bend of
the trap to the bottom of the leaving pipe
must be at least equal to one half of the X
dimension. This ensures that enough water
is stored in the trap to prevent losing the
drain seal during unit startup
Note: The absolute value of the fan inlet
pressure will always be greater than or equal
to the absolute value of the static pressure in
the drain pan on draw-through units, so the
fan inlet pressure is a safe value to use for
the drain pan static pressure.
Unit should not be operated without
p-traps. Failure to install a p-traps
may result in overflow of condensate
water.
CAUTION