Trane Tracer ZN524, Руководство по диагностике для владельца установки

Страница: 26 / 52

26 CNT-SVX11A-EN
Unit Operation
Cooling Operation
During the
COOLING
mode, the Tracer
ZN524 controller attempts to maintain
the space temperature at the active
cooling setpoint, which is one of the
following:
• Occupied cooling
• Occupied standby cooling
• Unoccupied cooling
The controller uses the measured space
temperature, the active cooling setpoint
along with the control algorithm to
determine the requested cooling capac-
ity of the unit (0-100%). The outputs are
controlled based on the unit configura-
tion and the requested cooling capacity.
Heating Operation
During the heating mode, the Tracer
ZN524 controller attempts to maintain
the space temperature at the active
heating setpoint, which is one of the
following:
• Occupied heating
• Occupied standby heating
• Unoccupied heating
The controller uses the measured space
temperature, the active heating setpoint
along with the control algorithm to
determine the requested heating capac-
ity of the unit (0-100%). The outputs are
controlled based on the unit configura-
tion and the requested heating capacity.
Fan Operation
The Tracer ZN524 controller also allows
the fan speed to be configured as auto.
When the fan speed switch is in the
auto position and the default fan speed
is configured as auto, the unit may
change between cycling and continu-
ous, depending on how the default fan
speeds are configured for heating and
cooling modes.
The fan mode request can be either
hardwired or communicated to the
Tracer ZN524 controller. When both are
present, the communicated request has
priority over the hardwired input.
During o
CCUPIED
,
OCCUPIED STANDBY
,
and
OCCUPIED BYPASS
modes, the fan
will operate as configured (cycling or
continuous). The fan may be controlled
off in these mode when the
MANUAL
OUTPUT TEST
has been initiated, a latch-
ing diagnostic is present, or the com-
municated or hardwired fan speed is
off.
During the U
NOCCUPIED
mode, the unit
fan is controlled off. When capacity is
required to maintain the
U
NOCCUPIED
heating or cooling setpoint, the unit fan
is controlled on until the
U
NOCCUPIED
setpoint is satisfied.
Fan Off Delay
If the fan is configured for cycling and
the heating output is controlled off, the
Tracer ZN524 Unit Controller automati-
cally holds the fan on for an additional
30 seconds. This 30-second delay gives
the fan time to blow off any residual
heat from the heating source.
Entering Water Temperature
Sampling Function
The Tracer ZN524 controller will sample
the Entering Water Temperature (EWT)
to determine proper control action for
units equipped with boilerless electric
heat or Waterside Economizer (WSE).
Each unit is treated as having isolation
valves - whether present or not. If the
EWT is communicated to the controller
via a BAS system, then no sampling
will be required.
If the EWT is present as a hardwired
input and communicated from a BAS,
the communicated value will be used.
When the EWT sample is used, the iso-
lation valve on circuit 1 will be driven
open for 3 minutes and the EWT read-
ing will be taken at that time.
To avoid sampling each time a new
cooling/heating request is initiated, the
last EWT value recorded is used for the
next (1)hour. During boilerless control
heating, if setpoint has not been met
following the hour, a new EWT reading
is made and the appropriate control
action is taken.
During WSE and DX operation, the EWT
is refreshed as often as the analog
imput is polled. NOTE: If the WSE is dis-
able due to enable setpoint AND DX
cooling is in operation, DX cooling will
not be disabled until the load is met.
This will occur even if the EWT has
lowered to the point the WSE can be
used. Refer to the WSE documentation
for further details.
Sampling for Waterside Economizer
Units
EWT is used to determine if WSE opera-
tion is feasible. If the EWT meets the
configured Enable setpoint, WSE opera-
tion is possible.