Lennox MERIT Series Installation Instructions Manual page 31

6 - If unit will be started immediately upon completion of
installation, prime trap per procedure outlined in Unit
Start-Up section.
Condensate line must slope downward away from the
trap to drain. If drain level is above condensate trap,
condensate pump must be used. Condensate drain
line should be routed within the conditioned space to
avoid freezing of condensate and blockage of drain
line. If this is not possible, a heat cable kit may be
used on the condensate trap and line. Heat cable kit
is available from Lennox in various lengths; 6 ft. (1.8m)
- kit no. 26K68; 24 ft. (7.3m) - kit no. 26K69; and 50
ft.(15.2m) - kit no. 26K70.
Furnace with Evaporator Coil
Using a Separate Drain
Field Provided Vent
1" min. 2" max. above
condensate drain.
Condensate
Drain Connection
Evaporator Drain Line
(vent required)
FIGURE 45
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.
Furnace with Evaporator
Coil Using a Common Drain
Field Provided Vent
1" min. 2" max. above
condensate drain.
Condensate
Drain Connection
Evaporator Drain Line
(vent required)
Condensate Trap With Optional Overflow Switch
From Evaporator Coil
Drain
Do not use copper tubing or existing copper condensate
lines for drain line.
Page 31
FIGURE 46
HorizontalFurnace4" Min. to 5" Max.above
condensatedrain connection)
FurnaceCondensate
DrainConnection
Optional
FIGURE 47
CAUTION