Lighting and Operating Instructions

1.STOP! Read the safety information above on this label.

2.The gas valve must be shut off by putting the ON/OFF

switch to position “ ”. Wait five (5) minutes to clear out any gas. If you smell gas, STOP! Follow “B” in the safety information above. If you do not smell gas, go to the next step.

3.This water heater is equipped with a safety pilot burner and an automatic ignition control system.

4.Set the ON/OFF switch (flip down cover plate on front

panel strip) to the “ ” position. In this position, the water heater is ready to use.

5.If the red LED indicator light is flashing, this is a warning that the water pressure is not enough to ignite the main burner.

6.Turn the hot water faucet on to the minimum flow rate required to activate the heater. The automatic ignition system first ignites the safety pilot burner which then ignites the main burner in about 4 seconds.

7.The green LED indicator is on when the main burner is on.

8.The pilot flame will extinguish 10-30 seconds after the burners come on. The burners will remain on until the hot water tap is turned off.

NOTE: On a first time initial installation, existence of air in the gas supply line and in the water line may cause some ignition delay. In that case, repeatedly open and close the hot water tap in order to restart the ignition process until all the air has been purged.

TO TURN OFF GAS TO APPLIANCE

Turn off the manual lever on the gas supply line to the heater

and set the ON/OFF switch to the OFF ( ) position. See Fig 9.

SETTING THE WATER TEMPERATURE

The 125 HX LP and 125 HX NG water heaters have a gas control that modulates burner input in response to flow. Its purpose is to ensure that the hot water temperature will remain steady, although the water flow demand might vary (down to 1/2 gal/minute). To adjust the temperature on your 125 HX, turn on a hot water faucet to its maximum flow. At the water heater, turn the large knob located beneath the main gas control on the front of the heater all the way to the right (clockwise). See Fig 8. This will produce a temperature rise of approximately 90°F at flow rates between 0.5 and

2.0gallons per minute. Given that average incoming water temperatures are 50°F, this heater will produce approximately 140°F water at these flow rates. Turning the dial all the way to the left (counterclockwise) will produce a temperature rise of approximately 45°F for flow rates between

1.1and 3.7 gallons per minute. It is safest to select a comfortable temperature and not have to mix in cold water.

Fig. 8 - Temperature Adjustment Knob

The position you select on the temperature adjustment knob will depend on the temperature of the incoming water (50°F is average in the U.S.). In warm weather regions where the incoming cold water is generally warmer, or during the hot weather months in some other areas a midway setting on the temperature adjustment knob would produce a temperature rise of about 70°F, giving an output of approximately 120°F. At this setting, if it is still necessary, one could mix a small amount of cold water in a shower and have a comfortable shower at about 3 gallons/minute. During the colder months, or in cold climate areas, it might be necessary to set the control to the maximum position, all the way clockwise to the right.

If you supply the 125 HX, with preheated water (i.e.) in a solar installation the unit could overheat. It will then shut off on safety when the outlet temperature reaches 194°F. For this type of application, purchase a solar model 125B LPS or 125B NGS.

If the inlet water temperature to the water heater is very warm the heater can produce temperatures that may be found to be too hot. A temperature balance shower valve can automatically mix in cold water to reduce such hot water temperature, in the event of any temperature instability with the use of a temperature balance shower valve, refer to shower valve manufactures instructions for internal adjustment setting. Adjustments should be made to the hottest setting in the shower valve. Additionally the temperature control of the heater can be adjusted to produce a more comfortable hot water temperature.

To start and to shut down the appliance press the button “”.

The switch is located behind the flip down cover plate on the front panel strip.

- on

- off

Green light on = main burner on.

Green light off = main burner off.

If the red light is flashing, that means the water flow is not enough to ignite the burner.

Temperature Adjustment Knob

Decrease temperature	Increases temperature
and increase flow	and decreases flow
G661_004

Fig. 9 - Principles of Operation

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125HX LP, 125HX NG specifications

The AquaStar 125HX NG and 125HX LP are highly efficient gas tankless water heaters designed to meet the demands of modern households. With their compact size and advanced technology, these units provide an endless supply of hot water while maintaining energy efficiency. Both models cater to natural gas and propane applications, making them versatile options for various installations.

One of the standout features of the AquaStar 125HX series is its ability to deliver a powerful output of up to 199,000 BTUs, ensuring that multiple hot water outlets can operate simultaneously without a drop in temperature. Users can enjoy the convenience of hot showers, laundry, and dishwashing all at once, making it an ideal choice for busy families or households with high hot water needs.

These models incorporate a sophisticated modulating gas valve that adjusts the gas flow based on the demand for hot water. This technology not only optimizes energy consumption but also contributes to extended unit life by minimizing wear and tear on the components. The AquaStar 125HX units also come equipped with a patented electronic ignition system, which eliminates the need for a standing pilot light and reduces gas consumption.

Furthermore, the AquaStar 125HX NG and 125HX LP feature a durable heat exchanger constructed from high-grade copper, which enhances thermal efficiency and prevents corrosion. This ensures a longer lifespan and increased reliability for homeowners. Additionally, the units are compact and wall-mounted, allowing for flexible installation in various spaces, including tight utility closets or outside walls.

Safety is also a top priority, with built-in overheat protection and a freeze protection feature that ensures the unit remains operational even in colder climates. The AquaStar 125HX series operates quietly, allowing users to enjoy the benefits of hot water without the disruptive noise commonly associated with traditional water heaters.

In summary, the AquaStar 125HX NG and 125HX LP are leading choices in the tankless water heater market, combining efficiency, reliability, and innovation. Their impressive output, advanced technologies, and compact design make them suitable for modern living, ensuring homeowners have access to hot water whenever they need it. With these features, AquaStar continues to set a high standard in water heating solutions.