A.O. Smith 400A - Manual (Page 11)

WARNING
NEVER OPERATE THE HEATER UNLESS IT IS VENTED TO THE
OUTDOORS AND HAS ADEQUATE AIR SUPPLY TO AVOID RISKS OF
IMPROPER OPERATION, FIRE, EXPLOSION OR ASPHYXIATION.
VENT PIPE TERMINATION
NOTE: Before installing venting, determine place of vent pipe
termination. See Figure 5 and 6 before proceeding.
CAUTION
DO NOT TERMINATE THE VENTING WHERE NOISE FROM
THE EXHAUST OR INTAKE WILL BE OBJECTIONABLE. THIS
INCLUDES LOCATIONS CLOSE TO OR ACROSS FROM
WINDOWS AND DOORS. AVOID ANCHORING THE VENT AND
INTAKE PIPES DIRECTLY TO FRAMED WALLS, FLOORS OR
CEILINGS UNLESS RUBBER ISOLATION PIPE HANGERS
ARE USED. THIS PREVENTS ANY VIBRATIONS FROM BEING
TRANSMITTED INTO THE LIVING SPACES.
IMPORTANT
The vent system must terminate so that proper clearances are
maintained as cited in local codes or the current editions of the
National Fuel Gas Code, ANSI Z223.1/NFPA 54 or the Natural Gas
and Propane Installation Code, CAN/CSA-B149.1.
Do not terminate the exhaust vent terminal over public area where
condensate or vapor can cause nuisance or hazard.
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 LOCATION OF HEATER and CLEARANCES, and
with National Fuel Gas Code and local Codes.
IMPORTANT
Plan the layout of the vent system backwards from the vent
termination to the appliance.
WARNING
USE ONLY THE VENT TERMINALS SUPPLIED WITH THIS UNIT.
TERMINATION OF A VENT SYSTEM WITH A DEVICE OTHER THAN
THE SUPPLIED VENT TERMINATIONS WILL AFFECT SYSTEM
PERFORMANCE AND RESULT IN A SAFETY HAZARD.
DIRECT VENTING
The air intake provided on the unit contains an intake guard, see
Figure 7.
3"x 4" PVC REDUCER WITH INTAKE SCREEN
FIGURE 7.
WARNING
WHEN THE UNIT IS TO BE SETUP AS A DIRECT VENT,
THE INTAKE GUARD AND THE BALANCE PLATE MUST BE
REMOVED. THE INLET VENT PIPE MAY THEN BE GLUED TO
THE AIR INTAKE (see Figure 8) PROVIDED ON THE UNIT.
FIGURE 8.
DIRECT VENT TERMINAL INSTALLATION
IMPORTANT
4" VENT AND INTAKE TERMINALS ARE PROVIDED FOR
NEW INSTALLATIONS. FOR REPLACEMENT OF PREVIOUS
BTH 300 AND 400 WITH 3" TERMINALS, THE 4" TERMINALS
ARE RECOMMENDED, BUT THE EXISTING 3" VENT/INTAKE
TERMINALS ARE PERMITTED.
NOTE: TO PREVENT EXHAUSTING PRODUCTS FROM
CIRCULATING TO THE AIR INTAKE IN WINDY/COLD AREAS,
THE MAXIMUM PRACTICAL DISTANCE BETWEEN THESE TWO
TERMINALS IS RECOMMENDED.
IMPORTANT
WHEN LOCATING THE TERMINALS ON A SIDEWALL, THE
FOLLOWING SPECIFICATIONS PERTAINING TO TERMINAL
LOCATION MUST BE FOLLOWED.
1. The intake vent terminal and the exhaust vent terminal must
terminate on the same exterior wall and must be located at
a minimum of 24" (61cm) from the vertical centerline of the
exhaust vent terminal (see Figure 9). In colder climates
increasing the 24" (61cm) minimum to 48" (122cm) will
reduce possibility of frost over from side winds blowing
exhaust vapors to the air intake of the direct the vent and is
recommended for Canada.