heat-timer Mini-MOD-CNC Installation And Operation Manual page 13

INSTALL THE SENSORS
HEATING SYSTEM SENSOR (HSS) INSTALLATION
• Only use the Heat-Timer sensor included with the unit ( (P/N 904220-00).
• The sensor wires can be extended up to 500' using a shielded 2-conductor cable
(Belden #8760 or equivalent (#18/2)). Do not ground the shield at the sensor but at
the panel using one of the terminals marked with an "O".
• Do not run sensor wires in conduit with line voltage wiring.
• Install a 3/8"ID 1/2"NPT immersion well (P/N 904011-00 or equivalent).
• Insert the sensor in a well approximately 10' feet past the last boiler on the common
supply header but before any major takeoffs.
• The sensor must be located where it sees the output of all the boiler stages. If a
boiler is piped so that the sensor does not see its output, the Mini-MOD-CNC will
not sequence the boilers correctly.
• The sensor can also be installed on the return to the boilers after all major returns
and before any boiler. However, when setting the reset ratio and the offset, the user
must consider the temperature drop across the building loop.
OUTDOOR SENSOR INSTALLATION
• Only use the Heat-Timer sensor included with the unit (P/N 904220-00).
• Locate the sensor in the shade on the north side of the building. The sensor should
never be in direct sunlight.
• Be sure the location is away from doors, windows, exhaust fans, vents, or other
possible heat sources.
• The sensor should be mounted approximately 10' feet above ground level.
• Adhere the Outdoor Label provided to the back of the sensor base.
• Use the Enclosure Base bottom knockout for the conduit. Use the locknut to hold
the conduit and enclosure base together. Screw the cover to the base.
• If screws are used to affix the enclosure to the wall, make sure to seal around
the sensor and wall except from the bottom.
• The sensor wires can be extended up to 500' using shielded 2-conductor cable
(Belden #8760 or equivalent (#18/2)). Do not ground the shield at the sensor but at
the control using the terminal marked with an "O".
• Do not run sensor wires in conduit with line voltage wiring.
NOTE
Determining the proper location of the Outdoor Sensor is very important. The Mini-MOD-CNC will
base the heat on the outdoor temperature information it receives from this location. If the sensor is in
the sun, or covered with ice, its reading will be different from the actual outdoor temperature (od).
059102-00 REV. C
08 INSTALLATION
IMMERSION HEATING SYSTEM SENSOR
Immersion Well
3/8" ID 1/2" NPT
Shield
Heating System Sensor
NOTE
If the System Sensor can
not sense the correct water
temperature, the Mini-
MOD-CNC will not provide
comfortable heat levels.
OUTDOOR SENSOR
Seal around
sensor and wall
Mounting
screws
location
Outdoor
drip-hole
Conduit
HEAT-TIMER CORP.
Common Supply
Pipe
Sensor Probe
Outdoor Sensor
snap-in location
Shield not
connected
Outdoor Label on
back of Sensor
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