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Condensate Drain Piping
Unit is equipped with 2 or more condensate
drain pan connections. A drain line with p-
trap must be installed on every drain
connection, with the p-trap not to exceed 6"
from the drain connection. The lines must be
the same pipe size or larger than the drain
connection and pitched away from the unit at
least 1/8 inch per foot. An air break must be
used with long runs of condensate lines.
CAUTION
Unit must not be operated without a p-
trap. Failure to install a p-trap may
result in overflow of condensate water
into the unit.
All drain connections must be used and
individually trapped to ensure a minimum
amount of condensate accumulation in the
drain pans. ABS type cement must be used to
join the drain pipe connections.
Note: The drain pan connections are 1.5"
MPT fitting.
Condensate drain trapping and piping must
conform to all applicable governing codes.
Drainage of condensate directly onto the roof
may be acceptable in certain areas, refer to
local codes. If condensate is to drain directly
onto the roof a drip pad must be placed below
the drain to protect the roof from possible
damage.
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.
Draw-Through Coils
Figure 17 - Draw-Through Drain Trap
The X dimension on the draw-through trap
must 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
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.
the dirt
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