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• This sensor should be an immersion type sensor (HT# 904250-00
or #904220-00). It must be inserted in a well (1/2"NPT, 3/8" I.D.)
(HT# 904011-00). Both the sensor and the well must be ordered
separately.
• The Boiler Return Sensor should be located after all the returns to
the boiler merge.
• The sensor wires can be extended up to 500' using 18 AWG
2-conductor shielded cable (HT# 703001-01).
• Do not connect the shield at the sensor. However, connect it to
SMC terminal 31.
WIRING ThE POWER
Terminals (1) through (3)
• If possible, provide a dedicated circuit breaker for the SMC. Make sure
not to connect the SMC to a circuit breaker shared with high inductance
devices such as relays, pumps, fans, or motors.
• Bring the 120 VAC 60 Hz power wires through the enclosure left bottom
knockout.
• Connect the hot line to terminal 1 (L).
• Connect the neutral line to the terminal 2 (N).
• Connect the ground to Earth ground terminal 3 (G). Do not use the
neutral line as a ground.
• Heat-Timer recommends the installation of a Surge Suppressor and a
Power Switch before the Power Line connection for safety and ease of
service.
OUTPUT WIRING
• The SMC outputs do not source any power. If power is needed to a specific
output, a separate power source must be wired in series with the output.
• Each of the output relays can switch a 6A resistive load at 120 VAC or a 1A
inductive load at 120 VAC.
• Each of the output relays has a LED to represent its status.
WIRING SySTEM PUMP AND SLAB PUMP
• The Slab Pump is designed to circulate the water/antifreeze solution
through the slab radiant tubing.
• The System Pump circulates the boiler water through the boiler loop.
• A separate power source must be used to power each of the pumps. Use
the relay to make or break the power to the HOT (Line) connection to the
pump.
• The Slab Pump output has a Normally Open relay output.
• The System Pump output has a Normally Open (N.O.) and a Normally
Close (N.C.) outputs. Use the (N.O.) relay output to operate the pump.
12
voltage) must use a different
knockout, conduit, and path
120VAC
Each of the pump relays can
operate a maximum of ¼ HP
SMC Installation and Operation Manual
WARNING
Class 1 voltage wires (low
from any Class 2 voltage
wires (high voltage).
PWR
L N G
1 2 3
L
N
Earth
Ground
WARNING
pump. If a larger HP pump
is used, use a pump starter.
ALERT
Output relays do not source
any power.. A separate
power source must be used
when needed.
SYSTEM
PWR
PUMP
OR VALVE
L N G
1 2 3
4 5 6 7
120VAC
System
Pump
4
BURNER
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