40 UNT-SVX07B-EN
Installation—Mechanical
If the unit does not have a factory piping package, the factory attaches the sensor and coiled lead
wires to the piping side end panel. The installer should attach the sensor parallel to and in direct
contact with the supply water pipe.
Note: The installer is responsible to ensure the changeover sensor is installed in a location that
can sense active water temperature. Otherwise, the unit may fail to sense the correct
operating mode and disable temperature control.
When using field supplied three-way valves, install the changeover sensor upstream of the valve
on the supply water pipe. When using field supplied two-way control valves, install the changeover
sensor in a location that will detect active water temperature. The unit must always be able to sense
the correct system water temperature, regardless of the control valve position.
Note: The maximum length of the automatic changeover wire cannot exceed ten feet from the
control panel. If the sensor extends beyond the unit chassis, use shielded conductors to
eliminate radio frequency interference (RFI).
Automatic Electric Heat Lockout Switch
Two-pipe fan-coil units with auxiliary electric heat have an automatic electric heat lockout switch
that disengages the electric heat when hydronic heat enables. If the unit has a factory piping
package and electric heat, the factory attaches the switch to the supply water pipe. When the lockout
switch detects the supply water temperature above 95°F, it disengages the electric heat. This
eliminates electric heat and hydronic heat working simultaneously.
Figure 5. Attach the changeover sensor to the entering water pipe as shown for changeover to
work properly
Figure 6. Close-up view of the changeover sensor
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