Gas Piping - Lennox G51MP SERIES Installation Instructions Manual

CAUTION
DO NOT use a power driver to tighten screws which
secure condensate trap to cabinet. Screws should
be hand−tightened using a screw driver to avoid the
possibility of damage to the trap assembly.
3 − The condensate trap provided with the unit is
manufactured using ABS material. Use ABS to PVC
transition solvent cement to glue a field−provided PVC
coupling or PVC pipe to the trap. Install a tee and vent
pipe near the trap.
NOTE − The condensate trap drain stubs (both sides)
have an outer diameter which will accept a standard
3/4" PVC coupling. The inner diameter of each stub
will accept standard 1/2" diameter PVC pipe.
NOTE − Vinyl tubing may be used for condensate
drain. Tubing must be 1−1/4" OD X 1" ID and should be
attached to the drain stubs on the trap using a hose
clamp.
4 − Glue the field−provided drain line to the tee. Route the
drain line to an open drain. As an alternate, clear vinyl
tubing may be used to drain condensate away from
the trap. Secure the vinyl tubing to the drain stubs on
the trap using a hose clamp. Do not overtighten the
hose clamp.
Condensate line must be sloped downward away from
condensate trap to drain. If drain level is above con-
densate trap, condensate pump must be used. Con-
densate drain line should be routed within the condi-
tioned 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.
CAUTION
Do not use copper tubing or existing copper
condensate lines for drain line.
5 − If unit will be started immediately upon completion of
installation, prime trap per procedure outlined in Unit
Start−Up section.
6 − Glue the provided cap onto the unused condensate
drain line stub.
CONDENSATE ASSEMBLY
(DO NOT use power
O−RINGS
driver. Hand−tighten
using screw driver.)
CAP
SCREW
NOTE − Use screws to secure condensate trap to cabinet. DO
NOT apply glue to this joint. All other joints must be glued.

Gas Piping

If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet.
Do not exceed 600 in−lbs (50 ft−lbs) torque when at-
taching the gas piping to the gas valve.
1 − Gas piping may be routed into the unit through either
the left- or right-hand side. Supply piping enters into
the gas valve from the side of the valve as shown in
figure 48 or 48.
The Honeywell VR8205 gas valve requires a low inlet
pressure switch in LP/propane applications. A 4" BIP
nipple must be installed in the gas valve inlet when
right−side gas entry is used in LP/propane applica-
tions. See figure 47 or 48.
2 − When connecting gas supply, factors such as length of
run, number of fittings and furnace rating must be con-
sidered to avoid excessive pressure drop. Table 9 lists
recommended pipe sizes for typical applications.
NOTE − Use two wrenches when connecting gas pip-
ing to avoid transferring torque to the manifold.
Page 31
HI/LO SCREWS
VENT
TEE
NIPPLE
COUPLING
CLEAN−OUT ACCESS
(both sides)
CONDENSATE
TRAP
FIGURE 45
CAUTION
WARNING
IMPORTANT
NIPPLE