48
•
if
ICE BUILD TERMINATION
is set to the TEMP
option and the
ENTERING CHILLED WATER
temperature is less than or equal to the
ICE BUILD
SETPOINT
;
•
if
ICE BUILD TERMINATION
is set to the CON-
TACTS option and the ICE BUILD CONTACT
is
open;
•
if the
ICE BUILD TERMINATION
is set to the BOTH
(temperature and contacts) option and the
ENTERING
CHILLED WATER
temperature is less than or equal
to the
ICE BUILD SETPOINT
and the ICE BUILD
CONTACT is open.
The
ICE BUILD RECYCLE
on the OPTIONS screen
determines whether or not the chiller will go into an ice
build RECYCLE mode.
•
If the
ICE BUILD RECYCLE
is set to
DSABLE
(disable), the PIC III reverts to normal (non-ice build)
temperature control when the ice build function is
terminated by satisfying one of the above conditions.
Once ice build is terminated in this manner, it will not
be reinitiated until the next ice build schedule period
begins.
•
If the
ICE BUILD RECYCLE
is set to
ENABLE
, the
PIC III goes into an
ICE BUILD RECYCLE
mode,
and the chilled water pump relay remains energised to
keep the chilled water flowing when the compressor
shuts down. If the temperature of the
LEAVING
CHILLED WATER
later increases above the
ICE
BUILD SETPOINT
plus half the
RECYCLE
RESTART DELTA T
value, the compressor restarts,
controlling the chilled water/brine temperature to the
ICE BUILD SETPOINT
.
5.28.3 - temperature control during ice build
During ice build, the capacity control algorithm shall use
the
CONTROL POINT
minus .8 K for control of the
LEAVING CHILLED WATER
temperature. The
ECW
CONTROL OPTION
and any temperature reset option
shall be ignored, if enabled, during ice build. Also, the
following control options will be ignored during ice build
operation:
•
ECW CONTROL OPTIO
N and any temperature
reset options (configured on TEMP_CTL screen).
•
20 mA DEMAND LIMIT OPT
(configured on
RAMP_DEM screen).
5.28.4 - termination of ice build
The ice build function terminates under the following
conditions:
1. Time Schedule — When the current time on the ice
build time schedule (OCCPC0S) is not set as an ice
build time period.
. Entering Chilled Water Temperature — Ice build ope-
ration terminates, based on temperature, if the
ICE
BUILD TERMINATION
parameter is set to 0 (TEMP),
the
ENTERING CHILLED WATER
temperature is
less than the
ICE BUILD SETPOINT
, and the
ICE
BUILD RECYCLE
is set to DSABLE. If the
ICE
BUILD RECYCLE OPTION
is set to ENABLE, a
recycle shutdown occurs and recycle start-up depends on
the
LEAVING CHILLED WATER
temperature being
greater than the water/brine
CONTROL POINT
plus
the
RESTART DELTA T
temperature.
3. Remote Contacts/Ice Level Input — Ice build operation
terminates when the
ICE BUILD TERMINATION
parameter is set to 1 (CONTACTS) and the
ICE
BUILD CONTACTS
are open and the
ICE BUILD
RECYCLE is
set to DSABLE (0). In this case, the
ICE BUILD CONTACTS
provide ice level termination
control. The contacts are used to stop the ice build
function when a time period on the ice build schedule
(OCCPC0S) is set for ice build operation. The remote
contacts can still be opened and closed to start and
stop the chiller when a specific time period on the ice
build schedule is not set for ice build.
4. Entering Chilled Water Temperature and ICE BUILD
Contacts — Ice Build operation terminates when the
ICE BUILD TERMINATION
parameter is set to
(BOTH) and the conditions described above in items
and 3 for
ENTERING CHILLED WATER
tempe-
rature and
ICE BUILD CONTACTS
have occurred.
note:
It is not possible to override the
CHILLER START/
STOP, CONTROL POINT
, and
ACTIVE DEMAND LIMIT
variables from CCN devices (with a priority 4 or greater)
during the ice build period. However, a CCN device can
override these settings during -chiller lead/lag operation.
5.28.5 - Return to non-ice build operations
The ice build function forces the chiller to start, even if all
other schedules indicate that the chiller should stop. When
the ice build function terminates, the chiller returns to normal
temperature control and start/stop schedule operation. The
CHILLER START/STOP
and
CONTROL POINT
return
to normal operation. If the
CHILLER START/STOP
or
CONTROL POINT
has been forced (with a device of less
than 4 priority) before the ice build function started, when
the ice build function ends, the previous forces (of less than
4 priority) are not automatically restored.
5.29 - Attach to network device control
The Service menu includes the ATTACH TO NETWORK
DEVICE screen. From this screen, the operator can:
•
enter the time schedule number (if changed) for
OCCPC03S, as defined in the NET_OPT screen
•
attach the ICVC to any CCN device, if the chiller has
been connected to a CCN network. This may include
other PIC-controlled chillers.
•
upgrade software
Fig. 13 shows the ATTACH TO NETWORK DEVICE
screen. The
LOCAL
parameter is always the ICVC module
address of the chiller on which it is mounted. Whenever
the controller identification of the ICVC changes, the change
is reflected automatically in the BUS and ADDRESS
columns for the local device. See Fig. 7. Default address for
local device is BUS 0 ADDRESS 1.
When the ATTACH TO NETWORK DEVICE screen is
accessed, information can not be read from the ICVC on
any device until one of the devices listed on that screen is
attached. The ICVC erases information about the module
to which it was attached to make room for information on
another device. Therefore, a CCN module must be attached
when this screen is entered.
