AO Smith Commercial Gas Tankless Water Heater ATI-340H-P

WARNING: Turn off all electric power to the water heater if service is to be performed.

Turn the manual gas valve located on the outside of the unit to the off position.

Failure to follow these steps could lead to fire or explosion, resulting in personal injury or death.

The water heater cannot perform properly without sufficient inlet gas pressure. Below are instructions on how to check the inlet gas pressure. THIS IS ONLY TO BE DONE BY A LICENSED PROFESSIONAL.

Shut off the manual gas valve on the gas supply line.

Remove the screw from the pressure port which is located on the gas inlet of the water heater shown in the diagram on the right.

Connect the manometer to the pressure port and zero the manometer.

Re-open the manual gas valve. Verify that there are no gas leaks.

With all gas burning equipment off, take a reading of the static gas pressure and make a note of it.

WARNING! Turn off the electrical power supply and close the manual gas shutoff valve and the manual water control valve before servicing.

WARNING! Failure to do so could result in severe personal injury, or death.

Are all openings for combustion and ventilation air unblocked?

Is the venting system free of leaks, corrosion, blockages or damage?

Is the burner free of dust, lint, grease or dirt?

Is the area around the water heater clear? Are there any combustible materials, gasoline or any flammable vapors and liquids?

Is the relief valve discharging periodically due to thermal expansion in a closed water supply system?

If the relief valve discharges periodically, it may be due to thermal expansion in a closed water supply system. Contact the water supplier or local plumbing inspector on how to correct this situation.

Are the burner flames visually checked through the burner window in the burner assembly located at the middle of the water heater?

Close the manual gas shutoff valve.

Turn off power to the unit and wait a couple of seconds. Turn on again.

Wait 30 seconds, and then turn off power to the unit.

If the heater is part of an Easy-Link or Multi-Unit System, close the inlet and outlet water valves to isolate the heater.

Open all hot water taps in the house. When the residual water flow has ceased, close all hot water taps.

Have a bucket or pan to catch the water from the unit’s drain plugs. If Isolation valves are installed, open the drains to drain the water. If isolation valves are not installed, unscrew the two drain plugs (large and small) to drain all the water out of the unit. Do not lose the o-rings that will be on the two drain plugs.

Wait a few minutes to ensure all water has completely drained from the unit.

Clean the filter: Check the water filter located within the cold inlet. With a tiny brush, clean the water filter of any debris which may have accumulated and reinsert the filter back into the cold water inlet.