Trane HUV Installation Operation & Maintenance page 29

Water Valve Override
The ZN520 can be commanded via
the Rover service tool to open all
hydronic valves 100%. This allows
for the faster water balancing of
each unit and the entire system
when the command is sent global-
ly to all controllers. A properly bal-
anced system is essential for
proper and efficient operation.
Hydronic Coil Freeze
Protection (Freeze Avoidance)
Unit ventilator systems in cold cli-
mates need to take precautions to
avoid hydronic coil freeze-up. The
ZN520 does this from three differ-
ent aspects. Any of these methods
of protections will result in the unit
fan being disabled, the outside air
damper being shut, and the hy-
dronic valves being opened 100%.
UV-PRC001-EN
Controls
Tracer ZN520
The three methods of freeze avoid-
ance include:
1 A binary freeze protection
thermostat is mounted on
the coil and will cause a
latching diagnostic if the coil
temperature falls below
35 F.
2 An analog discharge air sen-
sor monitors the tempera-
ture of the air coming off of
the coil and if the tempera-
ture falls below 40 F the out-
side air damper is closed,
the fan is turned off and the
valves are fully opened.
3 When in the unoccupied
mode the ZN520 has an ad-
justable freeze avoidance
setpoint. If the outside air
temperature is below the
setpoint the unit will open
the valves to allow water to
flow through the coils.
Interoperability
Interoperability allows the owner
freedom to select multiple ven-
dors, and multiple products. With
this advantage, the owner can
choose the best products, the best
application, and the best service
from a variety of suppliers to meet
their evolving building control
needs in a cost effective manner.
Generic Binary Input/Output
The three generic binary inputs/
outputs are not part of the normal
control, but are actually controlled
through he Tracer Summit system
(when present) to issue com-
mands to the ZN520 control to turn
the generic inputs/outputs of add-
on equipment (such as baseboard
heating, exhaust fans, occupancy
sensor, lighting, etc.) on and off.
This binary port is not affected
when other binary diagnostics in-
terrupt unit operation.
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