A.O. Smith 1300, 200, 201, 2500, 2100, 1850, 1500, 1000 instruction manual Features/Controls

Example: A Genesis boiler is rated at 1,300,000 Btu/hr. input at sea level. At an altitude of 5,000 (1500m), the prejet orifices will decrease the input rate by 20% (= 4% x 5) to a new rating of 1,040,000 Btu/hr. (= 80% x 1,300,000 Btu/hr.) The input reduction is achieved by the prejet orifices through self-regulation.

FEATURES/CONTROLS

MULTI-STAGE FIRING AND CONTROL SYSTEM

ALL MODELS - The control system consists of three basic components: 1) Central Control Board 2) Ignition Control Board and 3) Display Board. The Central Control Board and Ignition Control Boards are located in the control box and can be accessed through panels on the left side and top of the unit. The Display Board is attached to the front jacket panel. The control system is a multi-stage control capable of managing three or four ignition stages. Three stage models include the 1000, 1300 and 1500. Four stage models include the 1850, 2100 and 2500. Every system will have one Central Control Board, one Display Board and either three or four Ignition Control Boards depending on the model. There will be one Ignition Control Board per stage.

The central control board contains a strip of dip switches which allow the user to control several system variables. Table 5 shows a summary of these options. Make sure the dip switches are in the appropriate position for the unit's application. Consult the Control System section of the manual for more information, see page 26.

DIP SWITCH CONFIGURATION TABLE

SW1 OFF		ON	SELECTION:
A	3 STAGE	4 STAGE	EITHER 3 OR 4 STAGE SYSTEM
B	3 TRIALS	1 TRIAL	EITHER 3 OR 1
C	NOIRI	IRI	WHETHER SYSTEM IS IRI OR
	GAS VALVE	GAS VALVE	STANDARD
D	INLET	TANK	INLET OR TANK AS
			CONTROLLING PROBE
E	NO EXTERNAL EXTERNAL		WHETHER EXTERNAL
	THERMOSTAT	THERMOSTAT	THERMOSTAT IS USED

FOUTLET 210°F OUTLET 240°F OUTLETMAXIMUMTEMPERATURE

G	190°F	220°F	MAX. SET-POINTTEMPERATURE
H	DEGREES°F	DEGREES°C	EITHER °F OR °C FOR DISPLAYED
			TEMPERATURE

Figure 2. Summary of Dip Switch Options.

DIFFERENTIAL PRESSURE SWITCH

The differential pressure switch ensures that a sufficient differential exists between the air pressure in the pre-mix chamber and the inlet of the burner for safe, low NOX combustion. The switch has two pressure taps marked "+" (positive) and "-" (negative). Silicone tubing is run from the positive pressure tap of the switch to a tap on the control panel to measure the air pressure in the pre-mix chamber. The negative pressure tap measures the pressure taken at the burner's auxiliary tube. Connections can be seen by removing the lower front jacket panel. It is important that this panel remain sealed at all times while the boiler is operating.

This differential pressure switch is normally open and closes when the combustion blower starts.

BLOCKED FLUE PRESSURE SWITCH

The blocked flue pressure switch ensures that the flue gas vent is clear. This pressure switch is normally closed and only opens on the fault conditions.

FLAME SENSOR

The flame sensor acts to prove the flame has carried over from the ignitor to the right-most burner. If no flame is sensed, the gas valve(s) will close automatically. If no flame is sensed on three ignition trials the boiler will lock out. Upon lockout, manually push the ENTER/RESET button on the display panel to restart the boiler.

WATER FLOW SWITCH

The Water Flow Switch is installed at the boiler outlet to prevent burner operation in the event of inadequate water flow through the boiler. The Water Flow Switch is a single pole, normally open switch that will close its contacts when increasing water flow rate is encountered. This switch is factory-set, but may require field adjustment. The contacts will open when the flow rate drops below the adjusted setting and the gas valve(s) will close turning off the gas to the burners.

LIMIT CONTROLS

CAUTION

LIMIT CONTROLS ARE SAFETY DEVICES AND ARE NOT TO BE USED AS A THERMOSTAT.

The GB/GW models incorporate an outlet water probe consisting of two limit controls:

1.An adjustable automatic reset limit control, that can be set to either 210°F (99°C) or 240°F (115°C) depending on the application.

2.A fixed manual reset limit factory set at 250°F (121°C). If the manual reset should open due to high temperature the gas valves will close and the unit will go into lockout.

If lockout occurs, manually push the ENTER/RESET push-button on the display panel to restart the boiler.

ON/OFF SWITCH

The ON/OFF switch is a single-pole, single-throw rocker switch. The switch provides 120VAC from the line source to the boiler.

COMBUSTION AIR BLOWER

Provides air for combustion process. The blower settings are adjustable through the use of the air shutter, however, blowers are set at the factory and should not need adjustment.

TANK PROBE

FOR HOT WATER SUPPLY SYSTEMS (GW models), A tank probe is supplied with each hot water supply boiler. The inlet water temperature will default to the tank temperature on the display when the tank probe is installed.

Note: Tank Probe must be designated as controlling probe using Dip Switch "D" on Central Control Board before it can be used for (GW) hot water supply applications.

"Pigtails" of field-supplied wires should be spliced to "pigtails" of tank probe and connected to terminal block in the 24 volt junction box. See figure 12 for the tank probe installation. Follow the instructions for the operation and temperature setting procedures for the tank probe (see page 29).

FOR HOT WATER HEATING SYSTEMS (GB models) Due to the

many various types of systems and operating conditions, a tank

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