Checking The Draft - A.O. Smith 315456-002 Installation Instructions And Use And 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 9 page 31).
Sequence of Operation
CALL FOR
HEAT INDICATED
BY FLASHING OF
DISPLAY SCREEN
STATUS CODES
CONTROL CHECKS TO ENSURE
PRESSURE SWITCH IS OPEN
DRAFT BLOWER IS ENERGIZED
CONTROL CHECKS TO ENSURE
PRESSURE SWITCH IS CLOSED,
INDICATING BLOWER OPERATING
AND THERE ARE NO VENTING
BLOCKAGES (INLET OR OUTLET)
CONTROL ENERGIZES HOT
SURFACE IGNITER (HSI)
MAIN VALVE ENERGIZES ALLOW-
ING THE BURNER TO BE LIT BY
HSI, DRAFT BLOWER ENERGIZES
FLAME SENSE ROD DETECTS
FLAME OF MAIN BURNER
WATER IN TANK IS HEATED BY
MAIN BURNER AND
TEMPERATURE REACHES
THERMOSTAT SETTING
MAIN VALVE DE-ENERGIZES
AND DRAFT BLOWER CONTINUES
FOR A POST PURGE TIME OF
APPROX. 30 SECONDS
MAIN VALVE DE-ENERGIZES
AND BLOWER CONTINUES FOR
A POST PURGE TIME
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 are closed
when performing the draft test. Pass a match flame around
the relief opening of the draft hood. A steady flame drawn
into the opening indicates proper draft.
MATCH
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
DRAFT HOOD
RELIEF
OPENING
FIGURE 18.