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A surge condition occurs when the lift becomes so high that the gas flow across the impeller reverses.
This condition can eventually cause compressor damage. The envelope control algorithm notifies the
operator that chiller operating conditions are marginal and to take action to help prevent compressor
damage such as lowering entering condenser water temperature.
A high sound condition occurs in low guide vane position case, envelope control valve can be used to
decrease the sound level by opening this valve in low guide vane position case. To enable this function,
we need configure “high efficiency mode” to “disable” in CFGSURGE table. The default is low noise
mode(this mode is only valid for 19XR6&7)
5.10.1. Surge Prevention Control
The surge prevention control algorithm is an operator-configurable feature that can determine if lift
conditions are too high for the compressor and then take corrective action.
If Actual Lift is higher than reference lift, a capacity inhibit signal will be sent; If Actual Lift is higher than
reference lift plus surge line Upper Deadband, a capacity decrease signal will be sent; If Actual Lift is
lower than reference lift minus surge line Lower Deadband, these 2 signals will be canceled. Capacity
Control will respond to these 2 signals and make correction on VFD TARGET SPEED, EC valve actuator
IGV1 TARGET POSITION with the priority from high to low.
Before surge protection event occurs, if there is no surge prevention in the past 5 min, SURGE
PROFILE OFFSET will increment by 1. Reference lift will minus SURGE PROFILE OFFSET before
comparing to actual lift. SURGE PROFILE OFFSET is configurable in Surge Correction Configuration
Table.
5.10.2. Surge Protection
The Surge Protection algorithm will run after SURGE DELAY TIME elapsed when compressor has been
commanded to turn ON. It will compare the present PERCENT LOAD CURRENT value with the
previous value once every second. If the difference exceeds the maximum AMPS change value
(SURGE DELTA % AMPS + (PERCENT LOAD CURRENT / 10)), an incidence of surge has occurred,
and surge protection signal will be sent.
When an incidence of surge determined in this manner has occurred, the SURGE COUNTS will be
incremented by one. On receiving surge protection signal, Capacity Control will do correction by
modulating VFD TARGET SPEED, EC valve actuator IGV1 TARGET POSITION with the priority from
high to low.
When correction is in effective, Surge Protection Count will be increased by 1 when either one of IGV,
VFD or EC actuator is operated to do correction.
Guide vane should be inhibited for 1 minute after surge protection ends.
Chiller will do alarm shutdown under following conditions:
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