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determine the actual set point required and deliver the required
airflow to every terminal under the current load conditions. As
the conditions and airflow requirements at each terminal
change throughout the operating period, so will SP.RS and the
unit’s effective static pressure set point.
In the unlikely chance that both static pressure reset control
signals are simultaneously present, the CCN signal will take
precedence.
RELATED POINTS — These points represent static pressure
control and static pressure reset inputs and outputs. See Table 53.
Static Pressure mA (SP.M) — This variable reflects the value
of the static pressure sensor signal received by the
ComfortLink™ controls. It may in some cases be helpful in
troubleshooting.
Static Pressure mA Trim (SP.M.T) — This input allows a
modest amount of trim to the 4 to 20 mA static pressure trans-
ducer signal, and can be used to calibrate a transducer.
Static Pressure Reset mA (SP.R.M) — This input reflects the
value of a 4 to 20 mA static pressure reset signal applied to
TB203 terminals 6 and 7, from a third party control system.
Static Pressure Reset (SP.RS) — This variable reflects the
value of a static pressure reset signal applied from a CCN sys-
tem. The means of applying this reset is by forcing the value of
the variable SPRESET through CCN.
Supply Fan VFD Speed (S.VFD) — This output can be used
to check on the actual speed of the VFD. This may be helpful
in some cases for troubleshooting.
IGV Actuator Current Pos (IGV.P) — This output reflects
the current position of the supply fan inlet guide vanes. This
may be helpful in some cases for troubleshooting.
IGV Act. Commanded Pos (IGV.C) — This output reflects
the commanded position of the supply fan inlet guide vanes.
By comparing this to the actual position of the guide vanes, this
may be helpful in some cases for troubleshooting.
Fan Status Monitoring
GENERAL — The Z Series ComfortLink controls offer the
capability to detect a failed supply fan through either a duct
static pressure transducer or an accessory discrete switch. The
fan status switch is an accessory that allows for the monitoring
of a discrete switch, which trips above a differential pressure
drop across the supply fan. For any unit with a factory-installed
duct static pressure sensor, it is possible to measure duct
pressure rise directly, which removes the need for a differential
switch. Any unit with an installed supply fan VFD or inlet
guide vanes will have the duct static pressure sensor as
standard.
SETTING UP THE SYSTEM — The fan status monitoring
configurations are located in Configuration
→
UNIT. See
Table 54.
Table 54 — Fan Status Monitoring Configuration
Fan Stat Monitoring Type (SFS.M) — This configuration se-
lects the type of fan status monitoring to be performed.
0 - NONE — No switch or monitoring
1 - SWITCH — Use of the fan status switch
2 - SP RISE — Monitoring of the supply duct pressure.
Fan Fail Shuts Down Unit (SFS.S) — This configuration
will configure the unit to shut down on a supply fan status fail
or simply alert the condition and continue to run. When config-
ured to YES, the control will shut down the unit if supply fan
status monitoring fails and send out an alarm. If set to no, the
control will not shut down the unit if supply fan status monitor-
ing fails but send out an alert.
SUPPLY FAN STATUS MONITORING LOGIC — Regard-
less of whether the user is monitoring a discrete switch or is
monitoring static pressure, the timings for both techniques are
the same and rely upon the configuration of static pressure
control. The configuration that determines static pressure
control is Configuration
→
SP
→
SP.CF. If this configuration is
set to 0 (none), a fan failure condition must wait 60 continuous
seconds before taking action. If this configuration is 1 or 2
(VFD or IGV), a fan failure condition must wait 3 continuous
minutes before taking action.
If the unit is configured to monitor a fan status switch
(SFS.M = 1), and if the supply fan commanded state does not
match the supply fan status switch for 3 continuous minutes,
then a fan status failure has occurred.
If the unit is configured for supply duct pressure monitoring
(SFS.M = 2), then
• If the supply fan is requested ON and the static pressure
reading is not greater than 0.2 in. wg for 3 continuous
minutes, a fan failure has occurred.
• If the supply fan is requested OFF and the static pressure
reading is not less than 0.2-in. wg for 3 continuous min-
utes, a fan failure has occurred.
Dirty Filter Switch — The unit can be equipped with a
field-installed accessory dirty filter switch. The switch is located
in the filter section. If a dirty filter switch is not installed, the
switch input is configured to read “clean” all the time.
To enable the sensor for dirty filter monitoring set
Configuration
→
UNIT
→
SENS
→
FLT.S to ENABLE. The
state of the filter status switch can be read at Inputs
→
GEN.I
→
FLT.S. See Table 55.
Table 53 — Static Pressure Reset Related Points
ITEM EXPANSION RANGE CCN POINT
SFS.S Fan Fail Shuts Down Unit Yes/No SFS_SHUT
SFS.M Fan Stat Monitoring Type 0 - 2 SFS_MON
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
Inputs
→ 4-20 → SP.M Static Pressure mA 4-20 mA SP_MA
→ 4-20 → SP.M.T Static Pressure mA Trim -2.0 → +2.0 mA SPMATRIM
→ 4-20 →SP.R.M Static Pressure Reset mA 4-20 mA SPRST_MA 0.0
→ RSET →SP.RS Static Pressure Reset 0.0-3.0 in. wg SPRESET 0.0
Outputs
→ Fans → S.VFD Supply Fan VFD Speed 0-100 % SFAN_VFD
→ ACTU → IGV.P IGV Actuator Current Pos 0-100 % IGV_RPOS
→ ACTU → IGV.C IGV Act. Commanded Pos 0-100 % IGV_CPOS