Checking The Draft - A.O. Smith HIGH EFFICIENCY ATMOSPHERIC VENTGAS WATER HEATER Use & Care Manual

Water Heater Operation
Figure 17 below shows the water heater's sequence of
operation when a call for heat is initiated. The ignition
control module will attempt to light the burner three times.
If the ignition control does not detect ignition it will enter
lockout mode, indicated by display flashing status code
(see status code 3 page 30 and/or status code 8 page 31).
SEQUENCE OF OPERATION
Call for heat indicated by
flashing of display screen
status codes.
Gas valve/thermostat will do a
relay check (relay clicks will be
heard).
Display will show temperature
set point during call for heat.
Draft Blower is energized.
System will verify pressure
switch operation and start a
5 second pre-purge, then air
intake fan will turn off.
Ignitor will start a 12 second
warm up period. "IGN" will
show on display.
Gas valve/thermostat will open
for 4 second trial for ignition
and fan will turn on.
Main burner flame is detected by
flame sense rod. Air intake fan
and main burner will continue to
operate until water temperature
inside the tank reaches
temperature set point.
Gas valve/thermostat is de-
energized and air intake fan
continues for a post purge time
of approximately 5 seconds.
Water heater returns to standby
mode.
FIGURE 17.

Checking the Draft

Do not touch vent.
Doing so can result in burns.
After successfully lighting the water heater, allow the unit
to operate for 15 minutes and check the draft hood relief
opening for proper draft (Figure 18). Make sure all other
appliances in the area are operating and all doors/windows
are closed when performing the draft test. Pass a match
flame or smoke around the relief opening of the draft hood.
A steady flame or smoke drawn into the opening indicates
proper draft.
Flue Products Vented
to Ouside of Building
Dilution Air
Draft Hood
Dilution Air
(Relief Opening)
The water heater must be installed according to all local and state
codes or in the adsence of local and state codes, the "National Fuel
Code"' ANSI Z223.1(NFPA 54)- current edition.
If the flame flutters or is blown out, combustion products are
escaping from the relief opening. If this occurs, do not operate
the water heater until proper adjustments or repairs are made
to the vent pipe system and/or air supply requirements.
21
WARNING
Burn Hazard
Dilution Air
Match
Air is drawn in for
combustion. Keep
area clean and free
from combustibles
and flammable vapors.
Outer Door
FIGURE 18.
6" Maximum
Air Gap
Floor Drain