Catalogue

UV-PRC004-EN 47
Controls
• Force the water valve(s) open to balance the hydronic system during installation set-up or
service.
Filter Maintenance. Filter status for the controller is based on the cumulative run hours of the
unit fan. The controller compares the amount of fan run time against an adjustable fan run hour
(stored in the controller) to determine when maintenance is recommended for the unit. The run-
hours value may be user edited as required (through Rover). The valid range for the fan run hours
limit is 0 to 5000 hours with a default of 600 hours. Once the run hours limit has been exceeded,
the controller generates a maintenance required diagnostic (unit will not shut-down). The user will
be notified of this diagnostic through the building automation system or when a Trane Service Tool
is communicating with the controller.
Active Dehumidification. On unit ventilators with reheat coils, the Tracer ZN520 can provide
active dehumidification to the classroom. This means that the classroom relative humidity can be
kept below an adjustable setpoint independent outdoor weather conditions. Indoor humidity levels
are recommended by ASHRAE to be kept below 60% in order to minimize microbial growth and
the life span of airborne illness causing germs.
Master Slave (Data Sharing). Because the Tracer ZN520 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 units might
share one zone sensor for both stand-alone (with communication wiring between units) and a
building automation system (see Figure 14).
Water Valve Override. The Tracer 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 globally to all controllers. A properly balanced system is
essential for proper and efficient operation.
Hydronic Coil Freeze Protection (Freeze Avoidance). Unit ventilator systems in cold
climates need to take precautions to avoid hydronic coil freeze-up. The Tracer ZN520 does this from
three different aspects. Any of these methods of protections will result in the unit fan being
disabled, the outside air damper being shut, and the hydronic valves being opened 100 percent.
The three methods of freeze avoidance 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 sensor monitors the temperature of the air coming off of the coil and
if the temperature falls below 40°F the outside air damper is closed, the fan is turned off and
the valves are fully opened.
Figure 14. Master slave system layout
Tracer ZN520
UV-PRC004-EN.book Page 47 Monday, February 4, 2013 11:01 AM