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7 - If a venting problem is found during any of the preced
ing tests, the common venting system must be modi
fied to correct the problem.
Resize the common venting system to the minimum
vent pipe size determined by using the appropriate ta
bles in Appendix G. (These are in the current stan
dards of the National Fuel Gas Code ANSI Z223.1.
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced
by SL297)
WATER
HEATER
OPENINGS
(To Adjacent
Room)
If an SL297UHNV furnace replaces a furnace which was commonly
vented with another gas appliance, the size of the existing vent pipe
for that gas appliance must be checked. Without the heat of the orig
inal furnace flue products, the existing vent pipe is probably over
sized for the single water heater or other appliance. The vent should
be checked for proper draw with the remaining appliance.
FIGURE 18
REPLACING FURNACE THAT
WAS PART OF A COMMON
VENT SYSTEM
Exhaust Piping (Figures 19, 20, 22 and 23)
The vent adapter must be must be attached to the exhaust
coupling on the furnace top panel. Use the provided bands.
See steps below.
1 - Remove the caution sticker from vent adapter.
2 - Fully insert vent adapter with both bands loosely at
tached on the furnace exhaust coupling.
3 - Insert PVC exhaust pipe through vent adapter. Ensure
vent pipe is fully seated into exhaust coupling.
4 - Tighten both top and bottom bands to 40 in lbs. See
5 - Tighten top band.
Route piping to outside of structure. Continue with installa
tion following instructions given in piping termination sec
tion.
FIGURE 19
Furnace
Top Band
(torque to 40in
−
lbs)
PVC
Exhaust Pipe
Vent Adaptor To Exhaust Coupling
Top Panel
Bottom Band
(torque to 40in
−
lbs)
Vent
Adaptor
Furnace
Exhaust Coupling
CAUTION
Do not discharge exhaust into an existing stack or
stack that also serves another gas appliance. If verti
cal discharge through an existing unused stack is re
quired, insert PVC pipe inside the stack until the end
is even with the top or outlet end of the metal stack.
CAUTION
The exhaust vent pipe operates under positive pres
sure and must be completely sealed to prevent leak
age of combustion products into the living space.
Vent Piping Guidelines
NOTE -
Lennox has approved the use of DuraVent
®
and
Centrotherm manufactured vent pipe and terminations as
an option to PVC. When using the PolyPro
®
by DuraVent or
InnoFlue
®
by Centrotherm venting system the vent pipe re
quirements stated in the unit installation instruction – mini
mum & maximum vent lengths, termination clearances,
etc. – apply and must be followed. Follow the instructions
provided with
PoyPro by DuraVent and InnoFlue by Cen
trotherm venting system for assembly or if requirements
are more restrictive. The PolyPro by Duravent and In
noFlue by Centrotherm venting system must also follow
the uninsulated and unconditioned space criteria listed in
table 23.
The SL297UHNV is installed as a Direct Vent gas central
furnace only.
