Unit installation

25
To limit stages through network writes, the points Run Status
→COOL→MAX.C and Run Status→HEAT→MAX.H are forced
on the network through CCN points MAXCSTGS and
MAXHSTGS respectively. Force these to the desired maximum
stages of cooling/dehumidification and heating, respectively. When
there is no force on these points, they automatically reset to allow
all cooling/dehumidification and heating stages to be used. These
points are reset at power--on/reset (POR).
When using the Loadshed POC to do Demand Limiting, the cool
and heat stage limits under both Redline and Loadshed conditions
can be set individually with configuration decisions. If the active
stages is greater then the loadshed or redline configurations when a
loadshed or redline command is given, the unit will remove stages.
Configuration→CCN→LDSH→S.GRP
This is the Loadshed Group Number and corresponds to the
loadshed supervisory devices that resides elsewhere on the CCN
network and broadcasts loadshed and redline commands to its
associated equipment parts. This variable will default to zero which
is an invalid group number. This allows the loadshed function to be
disabled until configured.
Configuration→CCN→LDSH→R.MXC
This configuration tells the unit the maximum cooling stages
allowed to be on during a redline condition.
Configuration→CCN→LDSH→S.MXC
This configuration tells the unit the maximum cooling stages
allowed to be on during a loadshed condition.
Configuration→CCN→LDSH→R.MXH
This configuration tells the unit the maximum heating stages
allowed to be on during a redline condition.
Configuration→CCN→LDSH→S.MXH
This configuration tells the unit the maximum heating stages
allowed to be on during a loadshed condition.
The two Demand Limiting methods can be active simultaneously.
The lowest cool and heat stage limits imposed by either method are
applied, and these ”effective stage limits” are shown in the points
CSTGLIMT (Run Status→COOL→LMT.C) and HSTGLIMT
(Run Status→HEAT→LMT.H), respectively. In normal running
mode, these limits will prevent stages from being added, or stages
to be removed, as applicable. In test mode, these limits are ignored,
and the user may continue to operate all stages. The point
MODEDMDL (Run Status→MODE→D.LMT)isusedtoshowif
any Demand Limiting is in effect that prevents the unit from
operating either cooling or heating at full--capacity.
NOTE: MODEDMDL may reflect that staging is NOT limited even
though Loadshed is active, or the network points are being forced, if
the stage limits in effect are not less than the stages present in the unit.
If a more drastic mode of Demand Limiting is required, the
network point HVACDOWN (Run Status→MODE→HV.DN) can
be used to prohibit the unit from selecting any HVAC mode, thus
preventing the operation of the supply fan, compressors, condenser
fans, and heat stages. This point must also be forced, and is reset
automatically when not forced, and at POR.
NOTE: HVACDOWN can be used as an immediate shutdown of
the unit before limiting capacity (ex. Generator switching).
Linkage
ComfortLink controls do not require any configuration settings to
establish linkage with a Linkage Coordinator. This is done
automatically when the unit’s bus and element address are
configured in the Linkage Coordinator’s LINKAGE configuration
table. The linkage information that is supplied to the ComfortLink
unit by the Linkage Coordinator is as follows:
S Reference zone temperature
S Reference zone occupied biased heating and cooling set points
S Reference zone unoccupied heating and cooling set points
S Composite occupancy mode
The unit will control the equipment based on this information and in
return will provide the Linkage Coordinator with the following data:
S Operating mode -- Cooling, Heating, Free Cooling, Fire
Shutdown Evacuation, or Off
S Supply--air temperature
S Optimal Start Bias time (Based on worst case zone)
This synchronization of data optimizes the efficiency of the unit
and the zones to operate at peak system performance at all times.
This information can be seen in linkage maintenance tables of the
Linkage Coordinator and the RTU; it is updated at approximately
1--minute intervals.
Cooling and heating operation is slightly modified during Linkage
control. A PID loop is run to calculate required stages. This is
necessary because in stand alone operation, the unit tries to
anticipate the space. With Linkage, the unit must try to satisfy the
demand as soon as possible. The PID configurations are in
Configuration→PID. These values have been field tested and the
default values should NOT BE CHANGED.
For information on set up and configuration, see the Space
Temperature Control--CCN Linkage text in the Controls Quick
Start section of this book.
For additional information on the Linkage Coordinator or Zone
Controllers, please refer to their appropriate manuals.
Alarm Handling
There are a variety of different alerts and alarms in the system.
Alerts are indicated by TXXX (where XXX is the alert number) on
the display and generally signify that the improperly functioning
circuit can restart without human interaction. If an alarm occurs,
indicated by AXXX (where XXX is the alarm number), the
damaged circuit will generally not restart without an alarm reset via
the Scrolling Marquee display or CCN.
The response of the control system to various alerts and alarms
depends on the seriousness of the particular alert or alarm. In the
mildest case, an alert does not affect the operation of the unit in any
manner. An alert can also cause a “strike.” A “striking” alert will
cause the circuit to shut down for 15 minutes. This feature reduces
the likelihood of false alarms causing a properly working system to
be shut down incorrectly. If three strikes occur before the circuit
has an opportunity to show that it can function properly, the circuit
will strike out, causing the shutdown alarm for that particular
circuit. Once activated, the shutdown alarm can only be cleared via
an alarm reset.
However, circuits with strikes will be given an opportunity to reset
their strike counter to zero. As discussed above, a strike typically
causes the circuit to shut down. Fifteen minutes later, that circuit
will once again be allowed to run. If the circuit is able to run for 1
minute, its replacement circuit will be allowed to shut down (if not
required to run to satisfy requested stages). However, the
“troubled” circuit must run continuously for a user defined time
(Configuration→COOL→RST.C) with no detectable problems
before the strike counter will be reset to zero. Default value is
5 minutes.
CCN Alarm Broadcast
Operators of CCN networks might not want to be notified of
“striking” alerts for refrigerant circuits until the circuit has been
shut down due to 3 strikes. Set the cooling configuration of Alert
Each Strike (Configuration→COOL→ALM.N on display,
ALM_NOW on CCN) to YES to broadcast each circuit strike alert.
Set Alert Each Strike to NO to broadcast only circuit shut down.
Alert Each Strike configuration is ignored during Service Test and
all alerts are broadcast.
Alarm Relay Output
The alarm relay output is a normally open 24 vac output between
field connection terminal board terminals C and X. Selection of
which alerts and alarms will result in closing of the alarm relay
may be set in the Alarm Relay Configuration
(Configuration→ALM.O). Setting a configuration to YES will
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