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INTRODUCTION
• This manual provides information necessary for the installation, operation, and maintenance of the
water heater.
• The model description is listed on the rating plate attached to the side panel of the water heater.
• Please read all installation instructions completely before installing this product.
• If you have any problems or questions regarding this equipment, consult the manufacturer or its
local representative.
• This equipment is an on-demand, tankless water heater designed to efficiently supply endless hot
water for your needs when properly sized and installed.
• These high efficiency models have a built-in secondary heat exchanger that absorbs latent heat
from the exhaust gas.
• The Indoor models are only to be installed indoors. The Outdoor models are only to be installed
outdoors.
• The principle behind tankless water heaters is simple:
Intake port
(Indoor only)
Exhaust HL
(Indoor only)
Exhaust thermistor
(Indoor only)
Hi limit switch
HX thermistor
(540HX3 only)
Bypass valve
(540HX3 only)
Flow sensor/
Water control
valve
Outlet
thermistor
X3™ Cartridge
*This diagram illustrates tankless water heater design concepts only and does not accurately represent the
water heater's physical description.
1.
A hot water tap is turned on.
2.
Water flows through the flow sensor, then through the X3™ Scale Prevention Technology cartridge.
3.
The computer initiates the fan motor and gas valve to let gas flow through the heater and sends a signal to
the igniter to create an ignition spark.
4.
The gas ignites and flames appear within the burner chamber.
5.
Water is heated as it flows through the heat exchanger.
6.
Using thermistors to measure temperatures throughout the water heater, the computer modulates the gas
and water valves to ensure proper output water temperature and hot water outflows.
7.
When the tap is turned off, the unit shuts down.
Cold
water
Hot water
inlet
outlet
Inlet thermistor
5
Page
Installation Manual
Exhaust
Secondary
heat exchanger
Primary
heat exchanger
Drain plug
detector
Burner
Igniter
Fan motor
Computer board
Gas valves
Condensate
drain port
Gas
Introduction
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