Installation and Maintenance Manual

Startup
96 UNT-SVX07D-EN
the economizer enable setpoint (absolute dry bulb), the
controller modulates the outdoor air damper (between the
active minimum damper position and 100 percent) to
control the amount of outdoor air cooling capacity. When
the outdoor air temperature rises 5°F above the
economizer enable point, the controller disables
economizing and moves the outdoor air damper back to its
predetermined minimum position based on the current
occupancy mode or communicated minimum damper
position.
Dehumidification (Tracer ZN520)
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 percent 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 ZN520)
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-SVX01G-EN, or the most recent
version.
Binary Inputs (Tracer ZN520)
The Tracer ZN520 controller has four available binary
inputs (see Table 30). Normally, these inputs are 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
Note: Th
e generic binary input can be used with a Tracer
Summit
™
building automation system only.
Each binary input default configuration (including
normally open/closed) is set at the factory. However, you
can configure each of the four binary inputs as normally
open or normally closed. The controller will be set
properly for each factory-supplied binary input end-
device. When no device is connected to the input,
configure the controller’s input as not used.
Table 29. Relationship between outdoor temperature
sensors and damper position (Tracer ZN520)
Outdoor Air
Temp. Modulating Outdoor 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 minimum
position
Closed
Present and
economizing
feasible
Economizing
minimum
postion to
100%
Economizing between
occupied standby
minimum position to
100%
Open &
economizing
when unit is
operating, closed
Present &
economizing
not feasible
Open to
occupied
minimum
position
Open to occupied
standby minimum
position
Closed
Table 30. Binary input configurations (Tracer ZN520)
Binary
Input Description Configuration
Controller Operation
Contact
Closed
Contact
Open
BI 1
Low temperature
detection
(a)
(a)During low temperature, condensate overflow, and fan status diagnos-
tics, the Tracer ZN520 control disables all normal unit operation of the
fan, valves, and damper.
Normally closed Normal Diagnostic
(b)
(b)Table 31, p. 97 shows the controller’s response to low temperature de-
tection, condensate overflow, and fan status diagnostics.
BI 2
Condensate
overflow
(a)
Normally closed Normal Diagnostic
(b)
BI 3 Occupancy Normally open Unoccupied Occupied
BI 3
Generic binary
input
Normally open Normal
(c)
(c) The generic binary input does not affect unit operation. A building au-
tomation system reads this input as a generic binary input.
Normal
(c)
BI 4 Fan status
(a)
N o r m a l l y o p e n N o r m a l D i a g n o s t i c
(d)
(d)If the fan mode input is in the off position or the controller is in the un-
occupied mode with the fan off, the fan status input will be open. A di-
agnostic will not be generated when the controller commands the fan
off. A diagnostic will only be generated if the fan status input does not
close after one minute from energizing a fan output or any time the input
is open for one minute. The controller waits up to one minute after en-
ergizing a fan output to allow the differential pressure to build up across
the fan.
Note: The occupancy binary input is for standalone unit controllers as an
occupied/unoccupied input. However, when the controller receives
a communicated occupied/unoccupied request, the communicated
request has priority over the hard-wired input.
UNT-SVX07_-EN.book Page 96 Friday, April 27, 2012 9:40 AM