Green Status Lights, Red Fault Lights

Figure 1. Dia-Scan II Display Board.

Green Status Lights

LED 1: Call for Heat

LED 2: Flow Switch

LED 3: Pressure Switch

LED 4: Ignitor Current

LED 5: Gas Valve

LED 6: Flame Sense

Red Fault Lights

LED 7: Ignition Fail

LED 8: Circulate Failure

LED 9: Blower Failure

LED 10: Blocked Inlet

LED 11: Blocked Flue

Water Temperature Set Lights

LED 12: Inlet Water Temperature *

LED 13: Outlet Water Temperature

LED 14: Inlet/Outlet Differential Temperature

LED 15: Set-Point Temperature

LED 16: Outlet/Set-Point Differential Temperature

* Defaults to tank probe temperature when tank probe is used.

Temperature Set-point Adjustment Procedure

The control board has a standard programmable temperature set- point range of 110°F to 240°F. The user can easily change the temperature set-point at any time by using the following procedure. In all cases, the boiler must be energized. The factory default set- ting is 180°F.

To change or view the current programmed temperature set-point value:

1.Press the SELECT push-button on the display board until both the Set-Pt LED (LED 15, see figure 1) and Outlet Water Tem- perature LED (LED 13, see figure 1) are illuminated.

2.The LED display will show the current set-point temperature.

3.Press and hold the ADJUST push-button. The displayed tem- perature will either increase or decrease. To alternate between increasing or decreasing the temperature, release then press and hold the ADJUST push-button.

4.When the desired set-point temperature is reached, release the ADJUST push-button.

5.Press the ENTER/RESET push-button once, this enters the selected set-point temperature into controller memory.

6.The appliance will now control the temperature to the desired set-point value.

NOTE: The boiler must complete a full cycle in order for the new setting to take effect. If the unit is turned off prior to a complete cycle the setting will be lost and the previous setting will remain in effect.

If the ADJUST push-button is held down long enough, the set-point will reach 110°F, the minimum value (or 240°F, the maximum value) and stop. At this point, if the desired set-point is not obtained, re- lease the ADJUST push-button and depress it again. The set-point value will now restart at 110°F (240°F) and once again increase (decrease) in value for as long as the ADJUST push-button is pressed.

Switching Differential Adjustment Procedure

To facilitate proper operation and maximize appliance performance, the control has a programmable operating switching differential or "hysteresis" about the set point. This means a call for heat will become active when the water temperature measured at the outlet temperature sensing probe (Probe #1) drops to the set-point value minus the switching differential value. The burner will remain on until the water temperature measured at probe #1 reaches the set- point value. The switching differential value is fully programmable from 5°F to 50°F using the push-button(s) located on the Display Board. The default is set at 20°F.

To change or view the current programmed switching differential:

1.Press the SELECT push-button on the display board until the Set-Pt differential LED (LED 16, see figure 1) is illumi- nated.

2.The LED display will show the current switching differential.

3.Press and hold the ADJUST push-button. The displayed value will either increase or decrease. To alternate between increas- ing or decreasing the switching differential, release then press and hold the ADJUST push-button.

4.When the desired switching differential is reached, release the ADJUST push-button.

5.Press the ENTER/RESET push-button once, this enters the selected switching differential value into controller memory.

6.The appliance will now control temperature utilizing the de- sired switching differential value.

If the ADJUST push-button is held down long enough, the switching differential setting will reach 5, the minimum value (or 50, the maxi- mum value) and stop. At this point, if the desired switching differen- tial is not obtained, release the ADJUST push-button and depress it again. The switching differential value will now restart at 5 (50) and once again increase (decrease) in value for as long as the ADJUST push-button is pressed.

Circulating Pump Adjustment Procedure

The Controller is factory set with a 45 second post circulate func- tion. Using the Display Board, the user has the capability to choose between a 45, 90, or 180 second post circulate time period, or turn the pump on continuously. This provides flexibility in selecting the post circulate time to meet specific application requirements, and improves the efficiency of the circulating pump operation.

GB/GW-500, GB/GW-650, GB/GW-750, GB/GW-400, GB/GW-200 specifications

A.O. Smith is a renowned name in the water heating industry, offering a wide range of products that cater to various residential and commercial needs. Among their standout offerings are the GB/GW-200, GB/GW-400, GB/GW-650, GB/GW-750, and GB/GW-500 models. Each model is designed with advanced technologies, ensuring optimal performance, energy efficiency, and reliability.

The GB/GW-200 model, with a capacity of 200 liters, is ideal for small to medium-sized households. It features a high-efficiency gas burner and an advanced electronic control system that ensures accurate temperature regulation. The unit also comes equipped with a glass-lined tank for enhanced durability and resistance against corrosion, extending its lifespan significantly.

Moving up in capacity, the GB/GW-400 model offers 400 liters of hot water storage, making it a preferred choice for medium to large households or small businesses. One of its key features is the multiple safety systems integrated into its design, including flame failure protection and temperature control features, making it both safe and reliable. Additionally, this model is equipped with a user-friendly digital display that allows for easy monitoring and adjustments.

The GB/GW-500 model takes it a step further with a capacity of 500 liters. Designed for larger applications, including commercial settings, it integrates A.O. Smith’s innovative heating technology for rapid recovery rates. This model stands out with its focus on energy efficiency, having an impressive Energy Factor rating that significantly reduces operational costs.

The GB/GW-650 and GB/GW-750 models cater to even larger needs, featuring capacities of 650 and 750 liters respectively. Both models are engineered with high-output burners, ensuring quick heating even during peak demand periods. Advanced insulation materials are used, enhancing thermal efficiency and minimizing heat loss, which translates to significant energy savings over time.

All these models feature A.O. Smith’s proprietary tankless technology, which allows for continuous hot water supply without the need for a large storage tank. This innovation not only saves space but also addresses the ever-increasing demands for hot water in modern households and businesses.

In conclusion, the A.O. Smith GB/GW series—GB/GW-200, GB/GW-400, GB/GW-500, GB/GW-650, and GB/GW-750—delivers reliable, energy-efficient water heating solutions suited for a variety of applications. With advanced safety features, user-friendly controls, and high energy efficiency ratings, these models are built to meet the demands of any modern water heating application, ensuring customer satisfaction and peace of mind.