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Return Water
Stack
System Pump
Domestic Hot
Water Pump
Header
Temperature Sensor
Domestic Hot Water
Temperature Sensor
or Switch
System
Supply Water
Domestic
Hot Water
Supply
Water Flow
Switch
Stack
Temperature
Sensor
Boiler Pump
Outside Air
Temperature
Sensor
Return
Temperature
Sensor
Building Automation
System
Hardwired Connections
Boiler On/Off
Switch
Low Water Cutoff Switch
High Limit Auto Reset Supply
Supply Temperature Sensor
Vestibule and Burner
Thermal Fuses
Min. & Max Air Press Switches
Variable
M
Combustion Air
Damper
Fresh Air
Supply
- Lockout Indicator
- Enable/Disable Input
- Boiler Running Contact (Optional)
- Remote Firing Rate 4-20mAdc
- Remote Setpoint 4-20mAdc
Flame Rod
Ignition
Transformer
FAN
Speed Fan
Boiler
Jacket
Modbus RS-485 Monitoring & Control:
- Enable/Disable
- Remote Firing Rate
- Remote Setpoint
Blocked Condensate Drain
Gas
Valve
Low & High
Gas Pressure
Switches
Fuel
Supply
Figure 3: Boiler Control