Water Heating Ignition Sequence

(Make sure gas and electric power are connected properly)

1.The ignition control module is powered and monitors the system, waiting for a call for heat from the thermostat.

2.The thermostat calls for heat by reading a resistance value within a given range directly proportional to water temperature.

3.The control Module:

a.Checks the pressure switch for an open circuit.

b.Energizes the blower.

c.Checks the pressure switch for a closed circuit to prove draft.

d.Sends line voltage to the hot surface igniter with a 20 second warm up period.

e.Opens the gas valve and checks the sensing rod for flame.

4.The burner heats the water to the desired thermostat setting.

a.The resistance in the thermostat rises to the value selected by the temperature setting.

b.The control module closes the gas valve and 5 seconds later, removes power from the blower.

5.Cycle is completed.

FIGURE 29.

CONTROL SEQUENCE - HOT SURFACE DIRECT IGNITION

Pre-purge	5	seconds.
HSI Warm-up	20 seconds.
Ignition Activation Period	4	seconds.
Flame Recognition Period	1	second.
Ignition Trial	4	seconds.
Interpurge	5	seconds.
Post-purge	5	seconds.
Retries	2
Reset from Lockout	1	hr.
Flame Sensing (Nominal)
HSI Off/Run Mode	4.0µ DC

HIGH ALTITUDE INSTALLATION

WARNING

INSTALLATIONS ABOVE 2000 (610 m) FEET REQUIRE REPLACEMENT OF THE BURNER ORIFICE IN ACCORDANCE WITH THE NATIONAL FUEL GAS CODE (ANSIZ223.1/NFPA 54).

FAILURE TO REPLACE THE ORIFICE WILLRESULTIN IMPROPER AND INEFFICIENT OPERATION OFTHE APPLIANCE, PRODUCING CARBON MONOXIDE GAS IN EXCESS OF SAFE LIMITS, WHICH COULD RESULT IN EXCESS OF SAFE LIMITS, WHICH COULD RESULT IN SERIOUS PERSONAL INJURY OR DEATH.

A.O. Smith builds models specifically for high altitude service. Please check the rating plate before making changes.

VENTING MANUAL RESET SWITCH

There is a venting manual reset switch located on the venting hood. If the switch is activated, it will not reset itself. Before resetting this reset switch, check for flue blockage and propriety of the venting systems. To reset, press the red button.

FIGURE 30.

MAINTENANCE

WARNING

DISCONNECT FROM ELECTRICAL SUPPLY BEFORE SERVICING UNIT.

FOR YOUR SAFETY, WATER HEATER SERVICE SHOULD BE PERFORMED ONLY BY A QUALIFIED SERVICE TECHNICIAN. READ THE GENERAL SAFETY INFORMATION SECTION FIRST.

GPDT, GPDH, GPDX specifications

A.O. Smith is a renowned leader in the manufacturing of water heating solutions, and its series of gas water heaters, including the GPDT, GPDH, and GPDX models, are emblematic of the company’s commitment to innovation, efficiency, and reliability.

The A.O. Smith GPDT series is characterized by its high energy efficiency and robust design. With a 40-gallon capacity, it utilizes a 0.67 energy factor, making it an ideal choice for both residential and light commercial applications. This model features a unique combustion system that minimizes emissions while maximizing hot water output. Equipped with a powered draft system, the GPDT series effectively vents combustion gases, improving air quality and lowering operational costs.

In contrast, the GPDH series is particularly notable for its compatibility with high-efficiency gas appliances. It employs a direct vent system, allowing for versatile installation options. The GPDH models also include advanced diagnostics and a LED display that simplifies monitoring and maintenance. With an enhanced insulation design, these heaters minimize heat loss, effectively optimizing performance and energy savings.

The GPDX series capitalizes on cutting-edge technologies to provide superior performance. With capacities ranging from 30 to 50 gallons, these water heaters are designed to meet varying needs. The GPDX is equipped with a dual-purpose valve that offers superior temperature control and safety features, ensuring user convenience and peace of mind. Its intuitive interface allows users to easily set their desired water temperature and monitor performance metrics.

One of the key characteristics that unify the GPDT, GPDH, and GPDX models is their commitment to durability. A.O. Smith incorporates high-quality materials and innovative engineering processes to enhance the longevity of their products. Each model features an impressive warranty, demonstrating the company’s confidence in their craftsmanship.

In conclusion, A.O. Smith's GPDT, GPDH, and GPDX gas water heater series offer a blend of efficiency, performance, and innovation. These models are equipped with advanced technologies designed to provide users with reliable hot water solutions while minimizing energy consumption. With their robust build, user-friendly features, and impressive warranties, A.O. Smith continues to be a top choice for those seeking dependable gas water heating solutions.