SG Series Boilers – Installation and Service Manual
14
Electrical Connections
For all electrical connections: Strip wire ends and insert into the terminal block. Tighten terminal screw
clamps to securely hold the wire.
CAUTION - Risk of damage to the controller - Do not apply power to any connections on terminal
block TB4. 24 Vac has been factory wired to terminals C-1 and HL-15.
Terminal
Block
Connections Name Description / Comments
BO & CM
Boiler Outlet
Sensor
Connect boiler outlet water temperature sensor to terminals
BO and CM (common). The Boiler Outlet Sensor must be
attached using a cable tie to the boiler outlet pipe.
BI & CM
Boiler Inlet
Sensor
Connect inlet water temperature sensor to terminals BI and
CM (common). The Boiler Inlet Sensor must be attached using
a cable tie to the boiler inlet pipe.
OS & CM
Outdoor
Sensor
Optional Outdoor Sensor (for Mode 4 and 5 only): Connect
Outdoor Sensor 070 to terminals OS and CM (common). The
Outdoor Sensor is installed on an exterior wall, typically facing
North, and above the snow line. It should be shielded from
effects of heat or cold to prevent false outdoor temperature
readings. Avoid direct sunlight, exhaust fans, appliance vents,
and excessive moisture.
SD & CM
Supply/DHW
Sensor
Optional (for Modes 2, 3, and 5 only). Connect a Supply or
DHW Sensor 071 to terminals SD and CM (common). The
Supply/DHW sensor is inserted into a thermowell on the DHW
tank or attached using a cable tie to the supply pipe.
AL & AL
Alarm Optional. The alarm contacts are a powered output, do not
apply power. Connect an alarm (beeper, light, or relay) with a
rating of 24 Vac and maximum 0.45 A to terminals AL and AL.
FS & FS
Flow Switch Not used. Leave Jumper 5-6 on TB4. For convenience, the
Flow Switch terminals have been relocated to terminal block
TB2, poles T1 & S. Do not apply power.
ST & R
Setpoint DHW
Demand
Optional Domestic Hot Water Aquastat (for Modes 4 and 5
only): Connect domestic hot water aquastat to terminals ST
and R. Closed is activation. Do not apply power.
TB4
HT & R
Heat Demand Connect Thermostat or Zone Valve End Switch to terminals
HT and R. Closed is activation. Do not apply power.
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