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WSHP-PRC001-EN 19
Direct Digital Controls
When the ZN510 or ZN524 controller is
linked directly to the Tracer Summit,
each Tracer Summit building
automation system can connect a
maximum of 120 Tracer ZN510 or
ZN524 controllers. See Figure 29 for
the Tracer ZN524 board.
Figure 29: Tracer ZN524 controller
Tracer ZN510 and ZN524
functions include:
Compressor Operation
The compressor is cycled on and off to
meet heating or cooling zone de-
mands. Single and dual compressor
units use the unit capacity and pulse
width modulation (PWM) logic along
with minimum on/off timers to deter-
mine the compressor’s operation. The
compressor is controlled ON for long-
er periods as capacity increases and
shorter periods as capacity decreases.
Random Start
To prevent all of the units in a building
from energizing major loads at the
same time, the controller observes a
random start from 0 to 25 seconds.
This timer halts the controller until the
random start time expires.
Reversing Valve Operation
For cooling, the reversing valve output
is energized simultaneously with the
compressor. It will remain energized
until the controller turns on the
compressor for heating. At this time,
the reversing valve moves to a
de-energized state. In the event of a
power failure or controller OFF
situation, the reversing valve output
will default to the heating
(de-energized) state.
Fan Operation
The supply air fan operates at the fac-
tory wired speed in the occupied or oc-
cupied standby mode. When switch is
set to AUTO, the fan is configured for
cycling ON with heating or cooling. In
heat mode, the fan will run for 30 sec-
onds beyond compressor shutdown in
both occupied and unoccupied mode.
Fan Run Timer
The controller’s filter status is based
on the unit fan’s cumulative run hours.
The controller compares the fan run
time against an adjustable fan run
hours limit and recommends unit
maintenance as required.
Data Sharing
The Tracer ZN510/ZN524 controller is
capable of sending or receiving data
(setpoints, fan request, or space tem-
perature) to and from other controllers
on the communication link. This al-
lows multiple units to share a common
space temperature sensor in both
stand-alone and building automation
applications.
Night Setback
The four operations of the Tracer
ZN510/ZN524 controller include occu-
pied, occupied standby, occupied by-
pass and unoccupied.
In an occupied situation, the con-
troller uses occupied heating and cool-
ing setpoints to provide heating and
cooling to the building. This occupied
operation is normally used during the
daytime hours when the building is at
the highest occupancy level.
In an occupied standby situation,
the controllers heating and cooling
setpoints are usually wider than the
occupied setpoints. This occupied
standby operation is used during day-
time hours when people are not
present in the space (such as lunch-
time or recess). To determine the
space occupancy, an occupancy sen-
sor is applied.
In an unoccupied situation, the con-
troller assumes the building is vacant,
which normally falls in evening hours
when a space may be empty. In the un-
occupied mode, the controller uses
the default unoccupied heating and
cooling setpoints stored in the control-
ler. When the building is in unoccupied
mode, individual units may be manu-
ally placed into timed override of the
unoccupied mode at the units wall
sensor. During timed override, the
controller interprets the request and
initiates the occupied setpoint opera-
tion, then reports the effective occu-
pancy mode as occupied bypass.
In the occupied bypass mode, the con-
troller applies the occupied heating
and cooling setpoint for a 120 minute
time limit.
High and Low Pressure
Safety Controls
The Tracer ZN510/ZN524 controller
detects the state of the high pressure
or low pressure switches. When a fault
is sensed by one of these switches, the
corresponding message is sent to the
controller to be logged into the fault
log. When the circuit returns to nor-
mal, the high pressure control and low
pressure control automatically reset. If
a second fault is detected within a thir-
ty-minute time span, the unit must be
manually reset.
Condensate Overflow
When condensate reaches the trip
point, a condensate overflow signal
generates a diagnostic which disables
the fan, unit water valves (if present),
and compressor. The unit will remain
in a halted state until the condensation
returns to a normal level. At this time,
the switch in the drain pan will auto-
matically reset. However, the control-
ler’s condensate overflow diagnostic
must be manually reset to clear the di-
agnostic and restart the unit.
Features and Benefits
ZN510 & ZN524 Controls