Operation; Prior To Start Up; Sequence Of Operation - AO Smith BTR120 Manuel D'instructions

Fire or Explosion Hazard
Gas line purging is required with new piping or systems in
which air has entered.
To avoid risk of fire or explosion purge discharge must not
enter into confined areas or spaces where ignition can occur.
The area must be well ventilated and all sources of ignition
must be deactivated or removed.
Read instruction manual before
installing, using or servicing
water heater.

PRIOR TO START UP

Installation and start up of this water heater requires abilities and
skills equivalent to that of a licensed tradesman in the field involved,
see Qualifications on page 6.
Do not place the water heater in operation if any part has been under
water. Immediately call a qualified service technician to inspect the
water heater and to replace any part of the control system and any
gas control which has been under water.
The following information will describe the Sequence of Operation
for this water heater.
1. Switch power on to unit.
2. Thermostat calls for heat.
3. Ignition Control performs diagnostic self check on system
components.
4. The Ignition Control begins the trial for ignition.
5. The Ignition Control turns on the Spark Igniter and opens the Pilot
Gas Valve.
6. The Ignition Control monitors the Flame Sensor during the ignition
trial period.
7. If the Ignition Control does not sense the pilot flame during the
ignition trial period, the Ignition Control shuts the Pilot Gas
Valve and turns off the Spark Igniter. Depending on the water
heater model, the Ignition Control will either retry the ignition trial
at step 4 or lockout the ignition sequence. If the ignition sequence

OPERATION

SEQUENCE OF OPERATION

25
Light the water heater in accordance with the Lighting and
Operation Instruction label on the water heater and in this manual
on pages 27 and 28.
The water heaters covered by this manual are equipped with
an electronic control system that automatically sequences
the Igniter, the 24 VAC Gas Valve, the Burner ignition, and
flame sensing.
Before attempting start up, thoroughly study and know the exact
Sequence Of Operation. See written Sequence Of Operation on
page 25 and Sequence Of Operation Flow Chart on page 26.
Be certain that the water heater is full of water, that air is purged
from the gas and water lines and that there are no leaks in the
gas and water lines. Ensure all inlet water valves are open.
FILLING THE WATER HEATER
Follow these steps to fill the water heater prior to start up.
1. Close the heater drain valve.
2. Open a nearby hot water faucet to permit air in system to escape.
3. Fully open the cold water inlet valve allowing the piping and
water heater to fill with water.
4. Close hot water faucet opened in Step 2 as water starts to flow.
Read SEQUENCE OF OPERATION section of this manual prior
to lighting and operating this water heater.
With above conditions satisfied, start the unit in accordance with
the instructions on the operating label attached to the heater.
For your convenience a copy of the instructions are shown on
pages 27 and 28.
is locked out, the power to the unit must be cycled to restart the
Ignition Control.
8. If the pilot flame is proved during the ignition trial period, the
Ignition Control turns off the Spark Ignitor and opens the Main
Gas Valve.
9. The Ignition Control allows a 2 second pilot flame stabilization
period to insure that the pilot flame is not extinguished by the
main burner light-off process.
10. The Ignition Control monitors the Flame Sensor during the
heating cycle. If the flame signal is lost, the Ignition Control shuts
the Main Gas Valve and Pilot Gas Valve and re-starts the ignition
process at step 4.
11. Once the unit is satisfied, the Ignition Control will shut off the
Main Gas Valve and the Pilot Gas Valve and the unit will be in
standby mode until another call for heat is initiated by
the thermostat.
See the flow chart on page 26 for more information.