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Furnace with Evaporator Coil
Using  a Separate Drain
Drain
Field Provided Vent
1” min. 2” max. above
condensate drain.
Condensate
Drain Connection
Evaporator Drain Line
(vent required)
FIGURE 48 
 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.
Coil Using a Common Drain
Field Provided Vent
1” min. 2” max. above
condensate drain.
Evaporator Drain Line
(vent required)
Condensate
Drain Connection
FIGURE 49