Lennox MERIT ML193UH Installation Instructions Manual page 34

IMPORTANT
When combining the furnace and evaporator
coil drains together, the A/C condensate drain
outlet must be vented to relieve pressure in or-
der for the furnace pressure switch to operate
properly.
Condensate Trap With Optional Overflow Switch
From Evaporator Coil
(Upflow/Furnace 1" Min. to 2" Max.
Horizontal Furnace 4" Min. to 5" Max. above
condensate drain connection)
Optional
Overflow Switch
To Drain
FIGURE 57
Drain Pan
*Piping from furnace and evaporator coil must slope down a minimum of 1/4" per ft. toward trap.
Field−Provided Vent
Furnace Condensate
Drain Connection
ML193UH with Evaporator Coil Using a Common Drain
(Unit shown in horizontal left−hand discharge position)
Evaporator
Coil
Condensate Drain
Connection
ML193UH with
Coil Using a Common Drain
Field−Provided Vent
(1" min. to 2" Max. above
condensate drain connection)
Condensate
Drain Connection
4"min
5"max
5' max.
PVC Pipe Only
FIGURE 59
Page 34
Evaporator
Evaporator
Drain Line
Vent Required
FIGURE 58
Field−Provided Vent
(4" min. to 5" Max. above
condensate drain connection)