Lennox ML193UH Installation Instructions Manual page 29

Condensate Piping
This unit is designed for either right- or left-side exit of
condensate piping in upflow applications. In horizontal
applications, the condensate trap must extend below the
unit. An 8" service clearance is required for the conden-
sate trap Refer to FIGURE 44 and FIGURE 46 for con-
densate trap locations. FIGURE 52 shows trap assembly
using 1/2" PVC or 3/4" PVC.
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.
NOTE - Do not remove the rubber grommet used to
seal the cabinet on the side not used when installing
the condensate trap.
2 - Use a large flat head screw driver or a 1/2" drive
socket extension and remove plug (FIGURE 44)
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 appropriate pipe dope.
NOTE - Cold end header box drain plugs are facto-
ry installed. Check the unused plug for tightness to
prevent leakage.
3 - Install the cap over the clean out opening at the
base of the trap. Secure with clamp. See FIGURE
52.
4 - Install drain trap using appropriate PVC fittings,
glue all joints. Glue the provided drain trap as
shown in FIGURE 52. 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
sate trap, filter rack must be installed beyond
condensate trap or trap must be re-located to
avoid interference.
FIGURE 44
Rubber
Grommet
Plug
(same on left side)
Page 29
5 - FIGURE 47 and FIGURE 49 show the furnace and
evaporator coil using a separate drain. If necessary
the condensate line from the furnace and evaporator
coil can drain together. See FIGURE 48, FIGURE
50 and FIGURE 51.
Upflow furnace (FIGURE 50) - In upflow furnace appli-
cations 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 51) - In horizontal furnace
applications the field provided vent must be a minimum
4" to a maximum 5" length above the condensate drain
outlet connection. Any length above 5" may result in a
flooded heat exchanger if the combined primary 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 fit-
ting may be used for condensate drain. Attach to
the drain on the trap using a hose clamp. See figure
FIGURE 45.
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
Tubing
FIGURE 45
CAUTION
Do not use copper tubing or existing copper condensate
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 and 24 ft. (7.3m) - kit no. 26K69.
Barbed Fitting
Hose Clamp