Trane LO - Manual (Page 59)

UNT-IOM-6 59
Tracer ® ZN.520
Tracer ® ZN.520 is a communicating or standalone device. It is easily
accessible in the control end panel for service. The control end panel
is on the end opposite the piping.
Sequence of Operations
OFF: Fan is off; control valve options and fresh air damper options
close. The low air temperature detection option is still active.
Auto: Fan speed control in the auto setting allows the modulating (3-
wire floating point) or 2–position control valve option and three-speed
fan to work cooperatively to meet precise capacity requirement, while
minimizing fan speed ( motor/energy/acoustics ) and valve position
(pump energy, chilled water reset ). As the capacity requirement
increases at low fan speed, the water valve opens. When the low fan
speed capacity switch point is reached, the fan switches to medium
speed and the water valve repositions to maintain an equivalent
capacity. The reverse sequence takes place with a decrease in
required capacity.
Low/Med/High: The fan will run continuously at the selected speed
and the valve option will cycle to meet setpoint.
For Tracer ® ZN.520 controlled units that will interface with the Trane
Tracer Summit ® building management system, terminate the commu-
nication wiring in the control box at the designated terminals on the
board. Reference the unit wiring diagram or submittals.
Ground shields at each Tracer ® ZN.520, taping the opposite end of
each shield to prevent any connection between the shield and anther
ground. Refer to Trane publication, CNT-IOP-2 Installation, Operation
and Programming Guide, for the communication wiring diagram.
Communication wire must conform to the following specification:
1) Shielded twisted pair 18 AWG
2) Capacitance 23 (21-25 ) picofarads ( pF ) per foot
3) Listing/Rating – 300V 150C NEC 725-2 (b) Class 2 Type
CL2P
4) Trane Part No. 400-20-28 or equivalent, available through
Trane BAS Buying Group Accessories catalog.
Tracer Summit ®
Communication
Wiring
Tracer ® ZN.520