Daikin EWWD320, Installation, Operation And Maintenance Manual

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Use with On-Site Generators
Chillers are operated with variable frequency drives. These features make them especially appropriate for use in
applications where they may be required to run with on-site electrical generators. This is particularly true when the
generators are used for temporary power when the utility power is lost.
Generator Sizing :
Gas and diesel generators are sensitive to the compressor’s locked-rotor characteristics when the
chillers start up. Use the electrical data supplied with the performance output sheet for generator sizing purposes. The
chiller data sheet will show the RLA, which is for both compressors. Refer to Electrical Data to determine the LRA, based
on the RLA. It is important to size the generator to handle the LRA at start up.
Starting/Stopping Procedure : The stopping of the chiller in the event of a power failure should be uneventful. The
chiller will sense a loss of voltage and the compressors will stop, coasting down using power generated from their
dynamic braking to maintain the bearing magnetic field. The stop signal will initiate a three-minute stop-to-start timer,
effectively preventing compressor restart for three minutes. The timer is adjustable from three to fifteen minutes; the
recommended default value is three minutes. This interval allows the generator sufficient time to get up to speed and
stabilize. The chiller will restart automatically when the start-to-start timer expires.
Transfer Back to Grid Power : Proper transfer from stand-by generator power back to grid power is essential to avoid
compressor damage.
ATTENTION
Stop the chiller before transferring supply power from the generator back to the utility power grid. Transferring power
while the chiller is running can cause severe compressor damage.
The necessary procedure for reconnecting power from the generator back to the utility grid is shown below. These
procedures are not peculiar to Daikin units only, but should be observed for any chiller manufacturer.
1. Set the generator to always run five minutes longer than the unit start-to-start timer, which could be set from 15 to 60
minutes. The actual setting can be viewed on the operator interface panel on the Setpoint/Timer screen.
2. Configure the transfer switch, provided with the generator, to automatically shut down the chiller before transfer is
made. The automatic shut-off functio
n can be accomplished through a BAS interface or with the “remote on/off”
wiring connection. A start signal can be given anytime after the stop signal since the three-minute start-to-start timer
will be in effect.
Chiller Control Power : For proper operation on standby power, the chiller control power must remain as factory-wired
from a unit-mounted transformer. Do not supply chiller control power from an external power source because the chiller
may not sense a loss of power and do a normal shutdown sequence.
Unit description
This machine, of the water-cooled condenser type, is made up of the following main components:
Figure 8
– Unit main components