DESCRIPTION OF OPERATION
This appliance is one of the most advanced water
heaters available. It provides a continuous supply of
hot water at a preset temperature. This appliance is
direct vent where air is brought in from the outside and
combustion gases are exhausted to the outside.
While electricity, water, and gas supplies are connected,
this appliance produces hot water whenever a hot water
tap is open.
Ignition is electronic. There is no pilot light consuming
gas while the water heater is not being used. The gas
burner lights automatically when the hot water tap is
opened and goes out when the tap is closed. Installation
of the temperature controller is highly recommended.
The temperature controller can set the temperature
within a specific range and can provide error codes to
diagnose any problems.
The temperature of the outgoing hot water is constantly
monitored. This appliance may adjust the water flow
in order to maintain the temperature setting. The
water flow may vary from summer to winter due to the
difference in ground water temperature.
OPERATING INSTRUCTIONS
Sequence of Operation
1. Water Flow Begins
• Water Flow Sensor sends a pulse to the electronic
control board
• Electronic control board senses flow greater than
0.6 GPM
• Firing Sequence begins
2. Firing Sequence
• Electronic control board monitors inlet/outlet water
temperature, temperature set point, and water
flow rate.
• Combustion fan energized. Purges combustion
chamber.
• Spark igniter begins sparking.
• Gas control valve opens to minimum fire rate.
• Flame rod proves ignition
• Spark igniter stops sparking
3. Normal Operation
• Electronic control board monitors flame rod,
fan motor frequency, outlet water temperature,
controller temperature set point and water flow
rate.
• Gas control valve modulates gas input to required
firing rate.
• Combustion fan speed is adjusted for the required
firing rate.
• Water flow control valve is adjusted as needed.
4. Shutdown Sequence
• Electronic control board senses water flow rate
less than 0.5 GPM.
• Gas control valve closes.
• Water flow control valve resets to standby
position.
• Combustion fan runs for a short period of time at
low speed.
5. Standby Mode
• Electronic control board monitors water temperature
and remote controls
• Freeze protection is activated as needed.
Features Available on Temperature Controllers
The temperature controller is supplied with the
appliance. Dimensions (inches): 3.5 W x 4.75 H x 0.75 D.
In Use
Indicator
Temperature
Display
Thermostat
n
u
o Priority
—Hot water temp.
On/Off
Priority
Indicator
Priority
Button
ON/OFF
Button
Features Description
Error Codes When a fault is detected an error code
flashes at the temperature
In Use Indicator Indicates that hot water is being supplied
(i.e. a hot water tap is open).
ON/OFF Button Used to turn the water heater ON or OFF.
Priority Button /
Indicator
Indicates that this controller is setting the
temperature . Priority can be switched to
another controller by pressing its Priority
Button when no hot water is running.
Temperature Display Shows the temperature setting.
Thermostat Increases or decreases the temperature
setting.
Figure 13
24 305 & 505 Indoor Manual
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