Venting - A.O. Smith Gdhe 50 Instruction Manual

ventInG

Never operate the water heater unless it is vented to the outdoors.
The instructions in this section of the manual must be followed
to avoid choked combustion or recirculation of flue gases. Such
conditions cause sooting of the combustion chamber, burners and
flue tubes and creates a risk of asphyxiation.
For direct vent application where combustion air might be supplied
from extremely cold ambient through fresh air intake piping
system, it is recommended that a backflow preventer be installed
at the intake vent terminal close to the blower before proceeding
with installation of the rest of the fresh air intake piping. Call the
technical support phone number listed on the back cover of this
manual for more information.
vent pIpe terMInatIon
The first step is to determine where the vent pipe will terminate.
See Figures 15, 16, 17 and 18. The vent may terminate through a
sidewall as shown in Figures 15 and 16 or through the roof as shown
in Figures 17 and 18.
The vent system must terminate so that proper clearances are
maintained as cited in local codes or the current edition of the
National Fuel Gas Code, (ANSI Z223.1, 12.9.1 through 12.9.6).
See Figures 13 and 14.
Instructions on proper installation through a sidewall are provided
in Figures 15A, 15B, 15C, and 16.
Plan the vent system layout so that proper clearances are maintained
from plumbing and wiring.
Vent pipes serving power vented appliances are classified by
building codes as "vent connectors". Required clearances from
combustible materials must be provided in accordance with
information in this manual under FACTS TO CONSIDER ABOUT
LOCATION and INSTALLING THE WATER HEATER, and with the
National Fuel Gas Code and local codes.
plannInG the vent sYsteM
Plan the route of the vent system from the exhaust elbow to the
planned location of the vent terminal.
1. Layout total vent system to use a minimum of vent pipe and elbows.
2. This water heater is capable of venting flue gases equivalent to
45' (13.7 m) of 2" pipe, 128' (39 m) of 3" pipe as listed in Table 5.
number of
90° elbows
1
2
3
4
5
6
The minimum vent length for each pipe size is one 90° plus 2' (61
cm) of straight pipe and the appropriate termination.
note: The equivalent feet (m) of pipe listed above are
exclusive of the termination. That is, the termination, with
an installed screen, is assumed to be in the system and the
remainder of the system must not exceed the lengths discussed
above.
3. The exhaust elbow assembly is designed to accept only straight
sections of 2" pipe. To start, a minimum 2" (5.1cm) maximum
6" long of 2" pipe must be inserted and glued to the exhaust
elbow assembly if utilizing 3" vent pipe. Use the same method
with the blower inlet if a direct vent configuration is utilized.
If using 2" inch vent pipe:
A minimum of 2" (5.1cm) diameter vent pipe must be attached
to the exhaust elbow assembly. The total system cannot exceed
the lengths discussed above, where each elbow is equal to 5
equivalent feet (1.5m) of straight pipe.
If using 3" inch vent pipe:
Two inches (5.1cm) of 2" pipe must be attached to the exhaust
elbow assembly before adding a reducer to acquire the desired
pipe diameter. An appropriately sized 45 degree elbow (supplied
locally-a schedule 40 DWV) vent terminal must be obtained with
an equivalent screen (supplied in vent kit). The total system
cannot exceed the equivalent pipe lengths discussed above
where each elbow is equal to 5 feet (1.5m) of straight pipe (3"
vent pipe).
note: This unit can be vented with PVC pipe materials (Cellular
Core ASTM-F891; DWV ASTM-D2665 or CSA B181.2; Schedule
40, 80, 120 ASTM-D1785 or CSA B137.3; or SDR Series
ASTM-D2241 or CSA B137.3), CPVC pipe materials (CPVC41
ASTM-D2846 or CSA B137.6; Schedule 40, 80 ASTM-F441 or
CSA B137.6; or SDR Series ASTM-F442), ABS pipe materials
(Schedule 40 DWV ASTM-D2661 or CSA B181.1 or Schedule
40 DWV Cellular Core ASTM-F628. The fittings, other than
the TERMINATION should be equivalent to PVC-DWV fittings
meeting ASTM D-2665 (Use CPVC fittings, ASTM F-438 for CPVC
pipe and ABS fittings, ASTM D-2661/3311 for ABS pipe). If CPVC
or ABS pipe and fittings are used, then proper cement must be
used for all joints, including joining the pipe to Termination (PVC
Material). If local codes do not allow the use of the PVC termination
when a material other than PVC is used for venting, then an
equivalent fitting of that material may be substituted if the screen
in the PVC terminal is removed and inserted into the new fitting.
20
table 5
2" Maximum 3" Maximum
pipe - ft. (m) pipe - ft. (m)
40 (12.19) 120 (36.57)
35 (10.66) 115 (35.05)
30 (9.14) 110 (33.52)
25 (7.62) 105 (32)
20 (6.09) 100 (30.48)
15 (4.57) 95 (28.95)