Lennox ML193UH Installation Instructions Manual page 30

NOTE - If necessary the condensate trap may be installed
up to 5' away from the furnace. Use PVC pipe to connect
trap to furnace condensate outlet. Piping from furnace
must slope down a minimum of 1/4" per ft. toward trap.
1 - Determine which side condensate piping will exit the
unit, location of trap, field-provided fittings and length
of PVC pipe required to reach available drain.
2 - Use a large flat head screw driver or a 1/2" drive socket
extension and remove plug (figure 46) from the cold
end header box at the appropriate location on the side
of the unit. Install provided 3/4 NPT street elbow fitting
into cold end header box. Use Teflon tape or appropri­
ate pipe dope.
3 - Install the cap over the clean out opening at the base
of the trap. Secure with clamp. See figure 54.
4 - Install drain trap using appropriate PVC fittings, glue
all joints. Glue the provided drain trap as shown in fig­
ure 54. Route the condensate line to an open drain.
Condensate line must maintain a 1/4" downward slope
from the furnace to the drain.
CONDENSATE TRAP AND PLUG LOCATIONS
(Unit shown in upflow position)
Trap
(same on
right side)
1-1/2 in.
NOTE - In upflow applications where side return
air filter is installed on same side as the conden­
sate trap, filter rack must be installed beyond
condensate trap or trap must be re-located to
avoid interference.
FIGURE 46
5 - Figures 49 and 51 show the furnace and evaporator
coil using a separate drain. If necessary the conden­
sate line from the furnace and evaporator coil can
drain together. See figures 50, 52 and 53.
Upflow furnace (figure 52) - In upflow furnace applica­
Plug
(same on left side)
Page 30
tions the field provided vent must be a minimum 1" to a
maximum 2" length above the condensate drain outlet
connection. Any length above 2" may result in a
flooded heat exchanger if the combined primary drain
line were to become restricted.
Horizontal furnace (figure 53) - In horizontal furnace
applications the field provided vent must be a mini­
mum 4" to a maximum 5" length above the condensate
drain outlet connection. Any length above 5" may re­
sult in a flooded heat exchanger if the combined pri­
mary drain line were to become restricted.
NOTE - In horizontal applications it is recommended to
install a secondary drain pan underneath the unit and
trap assembly.
NOTE - Appropriately sized tubing and barbed fitting
may be used for condensate drain. Attach to the drain
on the trap using a hose clamp. See figure 47.
6 - If unit will be started immediately upon completion of
installation, prime trap per procedure outlined in Unit
Start-Up section.
Field Provided Drain Components
Elbow
Tubin
g
FIGURE 47
CAUTION
Do not use copper tubing or existing copper conden­
sate lines for drain line.
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. Heating 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.
Barbed Fitting
Hose Clamp