A.O. Smith HYB-90N warranty Cleaning The Heat Engine, Flushing The Heat Exchanger Lime Build- Up

Remove the filter:

•Disconnect the electrical power to the water heater.

•Close the shutoff valves on both the hot-water and cold-water lines.

•Unlock the door by rotating the side lock counter- clockwise with a wide, slot screwdriver.

•Pop the top and bottom door pins by pushing the pins out, using a small screwdriver. Open the door.

•Open a nearby hot water faucet to depressurize the water tank.

•Drain the tank following the instructions in the “Draining The Tank” section.

•Unscrew the filter and clean by rinsing it under a faucet and scrubbing with a brush if required.

Heat

Engine

Cabinet

Water

Inlet Filter

Water Inlet

Fitting

FIGURE 38

Install the filter:

•Install the clean filter.

•Close the drain valve.

•Open the shutoff valves on both the hot-water and cold-water lines.

•Fill the tank following the instructions in the “Filling The Water Heater” section in this Manual.

•Close and lock the door.

•Reconnect the electrical power to the water heater.

•Restart the water heater following the Lighting Instructions found in the Operating Manual.

CLEANING THE HEAT ENGINE

It is imperative that the control compartment burner and circulating air passageways of the appliance is kept clean.

•Turn off and disconnect the electrical power. Allow to cool.

•Remove and clean the water inlet filter. See “Cleaning The Inlet Water Filter” section.

•Remove the front panel.

•Use a low air pressure to remove dust from the main burner, heat exchanger, and blower. Do not use a wet cloth or spray cleaners on the burners.

NOTE: Do not use volatile substances such as benzene and thinners. They may ignite or fade the paint.

FLUSHING THE HEAT EXCHANGER (LIME BUILD- UP)

The heat exchanger must be cleaned on a regular basis to reduce lime build-up. The frequency of this cleaning is dependent on the quality of your local water supply. Failure to flush the appliance will cause damage to the heat exchanger. Damage caused by lime build-up is not covered by the unit’s warranty.

•Disconnect electrical power to the water heater.

•Close the shutoff valves on both the hot water and cold water lines.

•Drain the tank using the instructions in the “Draining The Tank” section.

•Disconnect the hoses joining the tank and the heat engine (upper hose is water outlet and lower hose is water inlet).

•Connect addition length of hose (not provided) to existing hoses. (Note: The heat engine hose is a 3/4” NPT thread which is different for a garden hose thread.)

5 gallon pail of virgin, food grade, white vinegar (or virgin, food grade,

citric acid).

Hot Water

Line

Heat

Engine

Cold Water

Line

FIGURE 39

•Connect a pump to the hose running to the heat engine water inlet (lower fitting). We recommend a submersible utility pump for the circulating pump. (Note: If a submersible pump is not used, connect a hose from the circulating pump to the cleaning solution.)

•Pour approximately 4 gallons (15 litres) of virgin, food grade, white vinegar or citric acid into a 5 gallon or greater pail.

•Place the “intake” and “output” hoses into the pail of cleaning solution. If a submersible utility pump is used, place the pump into the pail of cleaning solution.

•Plug in the circulating pump.

•Connect the electrical power to the water heater and run the heat engine.

•Operate the heat engine to circulate the cleaning solution through the system for at least 45 minutes. (Note: Lower the temperature below 104°F (40°C) or to vacation mode.) Warning: Water will become hot very

quickly.

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