A.O. Smith T-H2-DV User Manual

T-H2-DV/T-H2-OS Service Manual
Ver. 1.01
11
CONFIDENTIAL
5. Schematic diagram
The diagram below refers to both the T-H2-DV and T-H2-OS.
The T-H2-OS doesn’t have fan motor for exhaust, exhaust thermistor and hi-limit switch for
exhaust.
1. When a hot water tap is opened, cold water enters the T-H2-DV or T-H2-OS.
2. The water flow sensor detects this water flow and sends this information to computer.
3. The computer initiates fan motor and sends signal to igniter to create ignition spark.
4. The main, proportional, and solenoid gas valves open to allow gas input.
5. The gas ignites and flames appear inside the burner chamber.
6. Water circulates through the heat exchanger and is heated up to the set temperature.
7. Using thermistors to measure temperatures, the computer modulates the gas and water valves to
ensure proper output water temperatures.
8. When the tap is closed, the T- H2-DV or T- H2-OS shuts down.
*T-H2-DV controls fan motor for exhaust and detects the exhaust temperature by using exhaust
thermistor and hi-limit switch for exhaust during procedures of 3 to 8.
COLD
HOT
GAS
Condensate drain
Flow sensor
Output thermisotor
Inlet thermisotor
Bypasss vavle
Water control valve
Drain pan
Igniter rod
Air-fuel ratio rod
Hi-limit switch
Intake port
Primary heat exchanger
Exhaust
AC120V
PCB
ON-OFF-switch
for power supply
Transformer
Fuse box
Main gas vavle
Gas proprotional valve
Gas solenoid valve 1
Freeze protection thermostat
Gas solenoid valve 2
Heater
Fan motor
for combustion
Igniter
Gas solenoid valve 3
Flame rod
Mixing thermistor
Secondary heat exchanger
Fan motor
for exhaust
Hi-limit switch
for exhaust
Exhaust thermistor

A.O. Smith T-H2-DV Specifications

General

Brand	A.O. Smith
Model	T-H2-DV
Category	Water Heater
Language	English