Features And Components; Blower/Burner Assembly Detail; Basic Operation - A.O. Smith BTH-120 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
3 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
3 INCH PVC
BLOWER
FLANGE
FLAME
SENSOR
MAIN
BURNER
(radial design)
HOT SURFACE
IGNITER
120,000 & 150,000 Btu/hr MODELS
COMBUSTION
BLOWER ASSEMBLY
FLAME
SENSOR
199,000 & 250,000 Btu/hr MODELS
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.
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 Volt Gas Valve. See the
Sequence Of Operation Flow Chart on page 59.
7
COMBUSTION
BLOWER
INTAKE AIR
(combustion air)
CONNECTION
3 INCH PVC
BLOWER
FLANGE
HOT SURFACE
IGNITER
MAIN
BURNER
(radial design)
figure 2