AAON M2-036 - Manual (Page 52)

52
All external devices must be powered via a
separate external power supply.
Example:
A total of 8 wires must be pulled 75ft to a
control the unit. What size wire should be
used?
According to the Table 2, 16 AWG allows
for 63ft (500 ft/8 wires) and 14 AWG allows
for 94ft (750 ft/8 wires). Thus, 14 AWG
should be used.
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 every
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. Blow-through coils
will have a positive static pressure in the
drain pan. The condensate piping on these
drain pans must be trapped to prevent
pressure loss through the drain.
Condensate drain trapping and piping should
conform to all applicable governing codes. Note: The drain pan connection is a 1” MPT
fitting.
Figure 18 - Draw-Through 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.
Table 7 - Drain Trap Dimensions
Unit should not be operated without
p-traps. Failure to install a p-traps
may result in overflow of condensate
water.
CAUTION