Trane Tracer ZN524, Руководство по диагностике для владельца установки

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CNT-SVX11A-EN 29
Unit Operation
Other Modes
D
EHUMIDIFICATION
The ZN524 controller controls the zone
to the active cooling setpoint using pro-
portional control. The ZN524 also con-
trols one stage of DX cooling in con-
junction with one stage of reheat. The
only supported dehumidification type
during this period is hot gas reheat.
The factory-supplied ZN524 supports
one binary output for the control of a
two-position hot gas reheat solenoid
valve. This valve is normally closed and
will open when energized providing the
flow of hot refrigerant gas through the
reheat coil. The reheat coil is sized to
provide neutral air at 75 F loop condi-
tion with 75 F dry bulb return air at 75%
relative humidity. When in the dehu-
midification mode, only the first stage
DX cooling will be allowed to run on
two stage units.
Active dehumidification can only occur
when the controller is in the cooling
mode. Active dehumidification is not
allowed in heating mode.
Dehumidification can be active during
all time of day schedules.
A humidity transmitter is used to meas-
ure the zone relative humidity and is
compared against the relative humidity
enable/disable setpoints. Relative
humidity level can be communicated to
the ZN524 from a Tracer Summit sys-
tem. The default values for dehumidifi-
cation enable is 60% relative humidity.
Disable point is 52% relative humidity.
These values are configurable.
To avoid subcooling the space if the
reheat is not sized properly or during
certain system conditions, a low limit
temp is established to exit dehumidifi-
cation mode. The low limit is the active
cooling setpoint in the O
CCUPIED
and
U
NOCCUPIED
standby modes.
In the U
NOCCUPIED
mode, the default
O
CCUPIED
cooling setpoint is used as the
low limit. This enables extended dehu-
midification during unoccupied modes
which allows sub-cooling the space to
the default O
CCUPIED
setpoint. If the
zone temperature reaches the low limit
the DX cooling and reheat will be
turned off. The zone temperature must
then rise 0.75 F above the low limit
before the DX cooling and reheat are
allowed to operate again.
Note: While in the dehumidification
mode, if there is a call for capacity
by the unit, the zone temperature
setpoint will take priority over the
relative humidity setpoints.
Dehumidification will occur during the
following:
• Unit mode = cooling
• Relative humidity > Enable setpoint
Reheat in the dehumidification mode is
utilized under the following conditions:
• Zone temp is above the active
cooling setpoint
• Zone temp error < 1.5 F above the
active cooling setpoint
The compressor will be energized 100%
of the time during dehumidification
mode. No pulse width modulation is
used during dehumidification.
Dehumidification will occur during the
following:
• Unit mode = cooling
• Relative humidity > Enable setpoint
Reheat in the dehumidification mode is
utilized under the following conditions:
• Zone temp is above the active
cooling setpoint
• Zone temp error < 1.5 F above the
active cooling setpoint
Compressor 2 will not be on at the
same time as the reheat solenoid. No
pulse width modulation is used during
dehumidification.
For both single and two-stage cool-
ing, the following conditions will cause
the ZN524 to transition out of dehumid-
ification mode:
• Relative humidity
[
disable setpoint
• Zone temp
á
1.5 F
• Unit mode = heating
Note: For both single and two-
stage cooling, the occupied cool-
ing and occupied heating setpoints
can be the same, which may create
some risk of switching over to
heating mode unless the transition.
D
EFROST
For defrost operation, a sensor is wired
to BIP 1. When a defrost condition is
detected, the compressor(s) are dis-
abled, and the unit is placed in the
DEFROST
mode.
During
DEFROST
the compressor(s) are
off, and the fan will continue to operate
as continuous. The unit will remain in
the
DEFROST
mode until the sensor
resets. The unit will return to
NORMAL
operation after the mode is discontin-
ued.
P
RE
-H
EAT
The Tracer ZN524 controller keeps the
2-position outdoor air damper closed
anytime during the
OCCUPIED
mode
when the space temperature is 3°F or
more below the heating setpoint.
The damper remains closed indefinitely
during morning pre-heat until the space
temperature is within 2°F of the effec-
tive heating setpoint. The unit runs at
full capacity until setpoint is met.