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OPERATION
Ice Mode Operation
In Ice mode, the compressor will load up at the maximum
possible rate that allows for stable operation of the refrigerant
circuit. The unit should start when LWT error is greater than the
Startup Delta T set point. The unit should shut down when LWT
error is 0 or less.
Unit Capacity Limits
Unit capacity limits are used to limit total unit capacity in Cool
mode only. Multiple limits may be active at any time, and the
lowest limit is always used in the unit capacity control.
Demand limit and network limit use a deadband around the
actual limit value, such that unit capacity increase is not allowed
within this deadband. If unit capacity is above the deadband,
capacity is decreased until it is back within the deadband which
is 7%.
The unit capacity will be adjusted as needed to meet the lowest
active limit, but the circuit cannot be turned off to meet a limit
lower than the minimum unit capacity.
Demand Limit
The maximum unit capacity can be limited by a 4-20 mA signal
on the Demand Limit analog input at the unit controller. This
function is only enabled if the Demand Limit set point is set to On.
As the signal varies from 4 mA up to 20 mA, the limit changes
linearly from 100% to 0%.
Network Limit
The maximum unit capacity can be limited by a network
command. This function is only enabled if the unit control source
is set to network. The signal will be received through the BAS
interface on the unit controller. This network limit command
directly sets a max unit capacity from 0% to 100%.
RapidRestore Option
RapidRestore is an option that can be added to WWV chillers.
The general purpose of the option is to allow the capability to
restart more quickly and to load faster than normal when power is
lost and restored.
Enabling
The RapidRestore option is enabled via the RapidRestore set
point on the unit configuration screen. Changing the setting to
'enable' will require the following to be true:
• RapidRestore module is present at address 22
• DI1 on the RapidRestore module has a signal
If either of the above conditions are no longer true for at least
five seconds, then the RapidRestore set point will be changed
to 'disable', effectively disabling the RapidRestore option in the
chiller.
DAIKIN APPLIED
Operation Following Power Cycle
The chiller will enter RapidRestore upon powering up when the
following conditions are met:
• RapidRestore is enabled
• Power failure lasts less than the value of the Max Power
Failure Time set point
• Power failure lasts at least one second (shorter power loss
may result in unpredictable operation)
• Unit is enabled
• LWT error is at least 1°C
RapidRestore will end if any of the following conditions occur:
• LWT error is less than 1°C
• Unit capacity = 100%
• Unit becomes disabled for any reason
• 10 minutes have passed since unit powered up
Unit Level Changes
Evaporator Recirculation Time
With a goal of starting the chiller within 30 seconds after power
is restored, the evaporator recirculation time must be trimmed
to account for the controller boot time. When RapidRestore is
triggered, the time value used for the evaporator recirculation
time will be 10 seconds. Note that the evaporator recirculation
time set point is not changed as a result of this.
Condenser Recirculation Time
Similar to the evaporator, the condenser recirculation time will
be trimmed to 10 seconds for RapidRestore. The condenser
recirculation time set point is not changes as a result.
Unit Capacity Control
The evaporator LWT error does not have to be more than the
start delta t value. If RapidRestore is active, that is considered
adequate for starting the chiller.
Circuit Level Changes
When RapidRestore is triggered, all compressor cycle timers are
cleared to allow for starting more quickly. The limitation of four
starts per hour is still in effect though, and will not be cleared by
the RapidRestore operation. Compressor speed increments will
be 2Hz (normally 1Hz).
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NAVIGATOR WWV/TWV
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