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Cool Mode Operation
In Cool Mode, unit capacity is adjusted via circuit staging
and capacity changes on each circuit. LWT error and
EWT pulldown rate are the primary factors in unit capacity
adjustments. This section details all the logic for unit capacity
control in Cool Mode.
Staging On
Unit capacity control will command the circuit to start if all of
the following are true:
• Unit State = Auto
• Evaporator Pump State = Run
• LWT error > Startup Delta T set point
Staging Off
Unit capacity control logic will command the circuit to shut
down if either of the following conditions are true:
• LWT error < -(Shut Down Delta T set point)
• LWT < LWT Target AND EWT < LWT Target
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 via cicuit staging
and capacity changes to meet the lowest active limit, but the
last running compressor 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%.
IOM 1264-1 • NAVIGATOR
®
MODEL WWV CHILLERS
RapidRestore
®
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. Changing the setting to 'enable' will require the
following to be true:
• RapidRestore
module is present at address 22
®
• DI1 on the RapidRestore
If either of the above conditions are no longer true for at least
five seconds, then the RapidRestore
to 'disable', effectively disabling the RapidRestore
the chiller.
Operation Following Power Cycle
The chiller will enter RapidRestore
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
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.
Unit Capacity Control
The evaporator LWT error does not have to be more than the
start delta t value. If RapidRestore
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
increments will be 2Hz (normally 1Hz).
30
u
f
nIT
unCTIons
Option
module has a signal
®
set point will be changed
®
option in
®
upon powering up when
®
is active, that is considered
®
operation. Compressor speed
®
www.DaikinApplied.com
®
®
is
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