A.O. Smith T-H3-DV Service Manual

13 Page
240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
Ver. 1.00
CONFIDENTIAL
5. Schematic diagram
The diagram below refers to both the Direct Vent Indoor models and Outdoor models.
1. When a hot water tap is opened, cold water enters the water heater.
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 water heater shuts down.
The Direct Vent Indoor models detects the exhaust temperature by using
exhaust thermistor and hi-limit switch for exhaust during procedures of 3 to 8.
NOTICE
HOT COLD
GAS
Hi-limit switch
Inlet drain
plug filter
Outlet thermistor
Drain plug
Main gas valve
Gas solenoid valve 2
Fan motor for combuson
Igniter
O.H.C.F
Flow adjustment valve
with Flow sensor
Gas proporonal valve
Gas solenoid valve 1
Gas solenoid valve 3
Heat exchanger thermistor
Inlet thermistor
Exhaust thermistor
Intake port
120
Exhaust
Secondary heat exchanger
Primary heat exchanger
Hi-limit switch for exhaust
540 (T-H3) models only
Drain pan
Condensate drain
PCB
ON-OFF-switch for power supply
Surge box
Bypass valve
Direct Vent Indoor models only
Flame rod
Igniter rod
Air-fuel rao rod
Heater
VAC

A.O. Smith T-H3-DV Specifications

General

Brand	A.O. Smith
Model	T-H3-DV
Category	Water Heater
Language	English