Lennox SIGNATURE SLP99UHV Installation Instructions Manual page 28

Drain Pan
IMPORTANT
When combining the furnace and evaporator coil
drains together, the A/C condensate drain outlet must
be vented to relieve pressure in order for the furnace
pressure switch to operate properly.
Drain Pan
Furnace with Evaporator Coil Using a Separate Drain
(Unit shown in horizontal left-hand discharge position)
Evaporator
Coil
Condensate
Drain Connection
(Trap at coil is optional)
Piping from furnace and evaporator coil must slope down a minimum 1/4" per ft. toward trap
Furnace with Evaporator Coil Using a Common Drain
(Unit shown in horizontal left−hand discharge position)
Evaporator
Coil
Condensat e Drai n
Connection
(Trap at coil is optional)
Piping from furnace and evaporator coil must slope
down a minimum 1/4" per ft. toward trap
4"min
5"max
5' max.
PVC Pipe Only
FIGURE 44
Furnace with Evaporator
Coil Using a Common Drain
(Trap at coil is optional)
(1" min. to 2" Max.above
condensatedrain connection)
Condensate
Drain Connection
4"min
5"max
5' max.
PVC Pipe Only
FIGURE 46
Page 28
Field Provided Vent
(4" min. to 5" max. above
condensate connection)
.
FIGURE 45
(4" min. to 5" Max.above
condensatedrain connection)
Evaporator drain
line required