Features And Components; Basic Operation - A.O. Smith 101 Series Instruction Manual

Basic operation

The water heaters covered in this manual have a helical coil
shaped heat exchanger that is submerged in the storage tank.
The water heater's main Burner is a radial design burner, it
is mounted on the top and fires downward through the heat
exchanger. This is a forced draft burner; hot burning gases are
forced through the heat exchanger under pressure and exit
through the exhaust/vent connection located at the bottom of the
water heater. See Figure 1 and Figure 2.
BLOWER
BURNER
ASSEMBLY
INTAKE AIR
(combustion air)
CONNECTION
4 INCH PVC
MAIN
BURNER
(radial design)
HEAT
EXCHANGER
HELICAL
COIL
VENT (exhaust)
OUTLET

features and components

figure 1
Blower/Burner assemBly detail
INTAKE AIR
(combustion air)
CONNECTION
4 INCH PVC
BLOWER
FLANGE
FLAME
SENSOR
MAIN
BURNER
(radial design)
HOT SURFACE
IGNITER
hot surface igniter
The control system energizes the Hot Surface igniter with 120
VAC during the igniter warm up period. When the igniter is
energized it produces sufficient heat, >1800°F (>982°C), to ignite
the main burner.
note: Care must be taken when handling the igniter to prevent
breakage.
During the igniter warm up period prior to ignition the control
system monitors the igniter current and must sense a minimum
of 2.0 AC amps for BTH 300 & 400 models and 2.7 AC amps for
BTH 500 models. See the Sequence Of Operation on page 54.
flame sensor
The control system also monitors the flame sensor to confirm
a flame is present at the main Burner. if a flame is not verified
during the ignition trial period (3-5 seconds) the control system
will immediately de-energize the 24 VAC Gas Valve. See the
Sequence Of Operation Flow Chart on page 55.
7
COMBUSTION
BLOWER
figure 2