DIFFERENTIAL PRESSURE SWITCH | COMBUSTION AIR BLOWER |
The differential pressure switch ensures that a sufficient differential exists between the air pressure in the
The 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 vent system is clear. This pressure switch is normally closed and only opens on fault conditions.
FLAME SENSOR
The flame sensor detects the flame presence on burner's ports. 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. In the event of a lockout, depress the SELECT button on the UIM 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. It is a normally open switch that will close its contacts when increasing water flow rate is detected. The water flow switch is
LIMIT CONTROLS
CAUTION
LIMIT CONTROLS ARE SAFETY DEVICES AND ARE NOT TO BE USED AS AN OPERATING CONTROL (THERMOSTAT).
The "G(B/W)" models incorporate an outlet water probe consisting of two limit controls:
1.An adjustable automatic reset limit control, that can be set as high as either 210°F (99°C) or 235°F (113°C) depending on the application.
2.A fixed manual reset limit (ECO) factory set at 244°F (118°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, push the SELECTION button on the UIM to restart the boiler.
ON/OFF SWITCH
The ON/OFF switch is a
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 might require slight adjustment depending on site installation.
TANK PROBE
FOR HOT WATER SUPPLY SYSTEMS (GW models), a tank probe is supplied with each hot water supply boiler.
Note: The tank probe must be designated as the controlling probe using dip switch "4" on Central Control Board (Figure 17) before it can be used for (GW) hot water supply applications.
"Pigtails" of
FOR HOT WATER HEATING SYSTEMS (GB models), a tank probe is not supplied with the GB models due to the many various types of systems and operating conditions. A tank probe can be used as an option to control loop temperature and unit staging. Additionally, the inlet temperature probe can be used as the loop thermostat in some heating applications. The tank probe connects to designated wires in the junction box at the rear of the boiler. Do not operate this boiler using the internal high limits only, use a tank probe or operating thermostat to control system temperatures.
Note: The tank probe or additional 24VAC devices must be identified using Dipswitches on Central Control Board before they are recognized as a part of the heating system; see Table 5. Refer to "Control System" section for more information about dipswitch settings.
CIRCULATING PUMP
The pump flow rate should not exceed the maximum recommended flow rate; see Table 5.
FOR HOT WATER SUPPLY SYSTEMS (GW models), ordered with the circulator as an integral part of the boiler; the pump has been lubricated at the factory, and future lubrication should be in accordance with the motor manufacturer's instructions provided as supplement to this manual.
FOR HOT WATER HEATING SYSTEMS (GB models or GW models ordered without circulator), the circulator is NOT provided and must be
LOW WATER CUTOFF (Not Supplied)
If low water level protection is required by the authorities having jurisdiction, a low water cutoff switch should be installed next to the boiler in the outlet water line as shown in "HYDRONIC INSTALLATION" section; see page 16. The switch should receive periodic (every six months) inspection to assure proper operation. A low water cutoff device of the float type should
be flushed every six months.
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