68 | P a g e
Two conditions must be met to stage in a VFD:
1. The system has decreased to a pressure equal to psi SETPOINT minus STAGE PSI LAG.
a. Primary Slave VFDs and Primary Master Drives will ignore the STAGE PUMP
DELAY parameter, and immediately stage in if the system pressure drops below the
threshold.
2. The time set by STAGE PUMP DELAY has expired. This delay allows a momentary drop in
system pressure without calling for a drive to stage in.
The procedure to stage a drive is described below:
1. The selected drive will be staged in. The selected drive is based on the order given in
2. Table 19 and Table 20 above. This will either close the Slave VFD’s corresponding relay or
move the Master VFD out from sleep mode.
3. The speed of the main pump will decrease to a value equal to MAX FREQUENCY minus the
corresponding STAGE FREQ REDUCTION.
4. The Master VFD will operate at a reduced speed for a period of time set by STAGE TIME.
5. When STAGE TIME has expired the system will resume normal constant pressure control.
Note: The Master VFD does NOT have corresponding STAGE FREQ REDUCTION or STAGE TIME
parameters.
Drives are de-staged when the drive has slowed the main pump to maintain control pressure and the
Slave VFD(s) causes a rise in pressure.
Three conditions must be met to de-stage a VFD:
1. The system psi has increased to the value set by psi SETPOINT plus DESTAGE PSI LAG.
2. The time set by DESTAGE PUMP DELAY has expired. This delay prevents de-staging VFDs
due to momentary pressure overshoot.
3. The Master drive frequency is between MIN FREQUENCY and the value of MIN FREQUENCY
plus DESTAGE MIN FREQ.
The procedure to de-stage a drive is described below:
1. The selected drive will be de-staged. The selected drive is based on the order given in
2. Table 19 and Table 20 above. This will either open the Slave VFD’s corresponding relay, or
set the Master VFD to sleep mode.
3. The frequency of the main pump will increase by DESTAGE FREQ BOOST.
4. The Master VFD will operate at an increased speed for a period of time set by DESTAGE
TIME.
5. When DESTAGE TIME has expired the system will resume normal constant pressure control.
Note: Setting PROGRAM RELAY 1 to setting 6, Jockey Pump, will cause Relay 1 to not participate in
lead/lag or multiplex control. The order pumps are staged or destaged will remain the same, except the
Master will skip Relay 1. Relay 1 will also never become the Default when it is set to the Jockey Pump
setting.
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