Evaporator Coil Drain Pan Clearances
A. Coil pan width plus insulation
thickness times 2
B. Bottom flange detail—can be
C. Gas furnace
If the plenum ductwork is larger than the drain pan in any
direction, the gaps between the drain pan and the plenum
walls must be closed off to avoid bypass of air around the
sides of the drain pan. Use field-fabricated sheet metal
angles wide enough to support the coil where the drain pan is
located and attach them to the inside of the plenum. The
drain pan will rest on the metal angles. If the connection
between the plenum and any duct occurs below the apex of
the coil, seal this seam with sealant.
Install Condensate Drains
Plastic Drain Pan
Do not use the coil pan that shipped with the unit on
an OIL furnace or any application where the temperature
of the drain pan may exceed 300ºF (149ºC). A high
temperature drain pan (Kit Numbers HTP-A, -B, -C and
-D for nominal widths of 14", 17¹⁄₂", 21" and 24¹⁄₂" [35.6,
44.5, 53.3 and 62.2 cm] respectively) should be used for
this type of application. A field fabricated metal drain
pan can also be used.
The drain pan has a primary and an optional secondary drain with
³⁄₄" NPT female connections. The connectors required can be ³⁄₄"
NPT male PVC or metal pipe and should be hand tightened to a
torque of approximately 37 in/lbs to avoid damage to the drain
pan connection. An insertion depth between 0.355" to 0.485"
(0.9 cm to 1.2 cm) (3 to 5 turns) should be expected at this
torque. If the secondary drain line is required, it must be run
separately from the primary drain and should end where it is
easily seen. Water coming from this line means the coil primary
drain is plugged and needs clearing.
D. Field fabricated support for
E. 2" (5.1 cm) from top of furnace to
bottom of coil pan. Must be 6"
(15.2 cm) for oil furnaces.
F. Coil support
A trap must be installed in the drain line below the bottom of the
drain pan. If a copper drain line is used, solder a short piece of
pipe to the connector before installing a drain fitting.
NOTE: Do not over-torque the ³⁄₄" copper connector to the plastic
When completing the drain line, use a wet rag or heat sink
material on the short piece of pipe to avoid damage to the plastic
A. Air handler
B. Drain connection
C. Positive liquid seal required at trap
Typical drain pipe routings to avoid interference with vent piping
are shown in the "Typical Drain Pipe Routing" illustration.
Typical Drain Pipe Routing
A. Secondary drain pipe routing
B. Primary drain pipe routing
Verify Orifice Size
IMPORTANT: The proper orifice size is dependent on indoor coil/
outdoor unit combination and application. Consult the outdoor
unit information to determine if the indoor unit has the correct
Connect Refrigerant Lines
Refrigerant lines must be connected by a licensed, EPA certified
refrigerant technician in accordance with established procedures.
Connecting refrigerant lines must be clean, dehydrated,
refrigerant-grade copper lines.
Evaporator coils should be installed only with specified line
sizes for approved system combinations.
Handle the refrigerant lines gently during the installation
process. Sharp bends or possible kinking in the lines will
cause a restriction.
2" (5.1 cm) Minimum
3" (7.6 cm)