Service manual

MSE Series Electric Boilers – Installation and Service Manual
8
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 or TB5, except L1 & L2.
Terminal
Block
Connections Name Description / Comments
L1 & L2
Line Voltage If L1 and L2 are not pre-wired, connect only 120 Vac, 60 Hz,
single phase power to terminals L1 (Hot) and L2 (Neutral) of
terminal block TB5.
TB5
P1 & P2
Pump Connect only 120 Vac, maximum 1/6 HP pump to terminals P1
and P2 of the terminal block TB5. If a pump horsepower larger
than 1/6 HP is used, change the pump fuse on the boiler based
on the pump rating. Do not use a pump requiring greater than 5A
or 600 VA.
HL & HL
High Limits Pre-wired (factory wiring). Two temperature high-limits (set at
239°F with automatic reset) are connected in series to terminals
HL and HL.
BO & CM
Boiler Outlet
Sensor
Pre-wired (factory wiring). Connect outlet water temperature
sensor to terminals BO and CM (common). The Boiler Outlet
Sensor is inserted into the thermowell on the right side of the tank
beside the boiler outlet.
BI & CM
Boiler Inlet
Sensor
Connect inlet water temperature sensor to terminals BI and CM
(common). The Boiler Inlet Sensor is attached by cable tie to the
boiler inlet pipe.
OS & CM
Outdoor
Sensor
Optional Outdoor Sensor (for Operation Mode 4 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 Operation Mode 3 only). Connect a Supply/DHW
Sensor 071 to terminals SD and CM (common). The Supply/DHW
sensor is inserted into a thermowell on the DHW tank or attached
by 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 Optional. Remove the jumper from the terminals FS and FS.
Connect flow switch to terminals FS and FS. Do not apply power.
ST & R
Setpoint
DHW
Demand
Optional Domestic Hot Water Aquastat (for Operation Mode 4
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.