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BCXC-SVX01B-EN 57
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temperature rises 5°F above the economizer enable point, the controller disables economizing and
moves the fresh air damper back to its predetermined minimum position based on the current
occupancy mode or communicated minimum damper position.
Tracer Dehumidification (Tracer ZN520 Only)
Dehumidification is possible when mechanical cooling is available, the heating capacity is located
in the reheat position, and the space relative humidity setpoint is valid.The controller starts
dehumidifying the space when the space humidity exceeds the humidity setpoint. The controller
continues to dehumidify until the sensed humidity falls below the setpoint minus the relative
humidity offset. The controller uses the cooling and reheat capacities simultaneously to
dehumidify the space. While dehumidifying, the discharge air temperature is controlled to
maintain the space temperature at the current setpoint.
A typical scenario involves high humidity and high temperature load of the space. The controller
sets the cooling capacity to 100% and uses the reheat capacity to warm the discharge air to maintain
space temperature control. Dehumidification may be disabled via Tracer™ or configuration.
Note: If the unit is in the unoccupied mode, the dehumidification routine will not operate.
Data Sharing (Tracer ZN510 or ZN520 Only)
Because this controller utilizes LonWorks® technology, the controller can send or receive data
(setpoint, heat/cool mode, fan request, space temperature, etc.) to and from other controllers on
the communication link, with or without the existence of a building automation system. This
applies to applications where multiple unit controllers share a single space temperature sensor (for
rooms with multiple units but only one zone sensor) for both standalone (with communication
wiring between units) and building automation system applications. For this application you will
need to use the Rover™ service tool. For more information on setup, refer to the Trane publication
EMTX-IOP-2.
Binary Inputs
Tracer™ ZN controllers have the following binary inputs, factory-configured for the following
functions:
• Binary input 1: low temperature detection (freezestat)
• Binary input 2: condensate overflow
• Binary input 3: occupancy/ generic
• Binary input 4: fan status (Tracer ZN520 only)
Note: The generic binary input can be used with a Tracer Summit®
building automation system
only.
BIP1: Low Temperature Detection Option
The factory hard wires the low temperature detection sensor to binary input #1 (BIP1) on the
Tracer™ ZN controller. The sensor defaults normally closed (N.C.), and will trip off the unit on a low
Table 26. Relationship between outdoor temperature sensors and economizer damper position (Tracer ZN520 only)
Outdoor air temperature
Modulating fresh air damper
occupied or occupied bypass Occupied standby Unoccupied
None or invalid Open to occupied minimum
position
Open to occupied standby minimum
position
Closed
Failed Open to occupied minimum
position
Open to occupied standby Closed
Present and economizer
feasible
Economizing: minimum position
to 100%
Economizing: between occupied
standby minimum position to 100%
Open and economizing only when
unit operating, closed otherwise
Present and economizer not
feasible
Open to occupied minimum
position
Open to occupied standby minimum
position
Closed