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FREQUENCY is 30 Hz and 1.5.6 DESTAGE MIN FREQUENCY is 5 Hz, the pump will destage at
35 Hz.
Pumps are destaged in the following sequence:
1. The system measured value will increase by the value set by 1.5.11 DESTAGE FREQUENCY
BOOST 1. This boost in motor power allows the PI constant pressure loop to react faster to the
drop in value when the pump turns off.
2. The system will destage the pump
3. The system will continue to boost the motor power set by 1.5.11 DESTAGE FREQUENCY BOOST
1 for a period set by 1.5.5 DESTAGE TIME.
4. The system will resume normal constant pressure control.
6.5 Duplex / Multiplex Control
Figure 22 – Connecting Duplex/Multiplex Systems
When any analog constant pressure system configuration is selected, the 1.4 CONSTANT PRESSURE
PARAMETERS and 1.5 LEAD LAG PARAMETERS menus are available. Up to four additional VFDs can be
controlled through the relays. When the parameter 1.5.1 NUMBER LAG PUMPS is greater than 0, relays will
convert to control of lead/lag or duplex/multiplex constant pressure in sequence. Example: If 2 lag pumps are
entered, Relay 1 & Relay 2 will now be used for Lead/Lag pump control. In addition, the constant pressure
parameter 1.4.41 DUPLEX CYCLE TIME must be greater than 0 for Multiplex control to be active.
When operating in Multiplex Control, the main VFD will assume the role of Master, and all auxiliary VFDs
controlled through the relays are known as Slaves. The Master and Slave VFDs will operate in constant
pressure mode.
If the Master VFD senses that system pressure cannot be maintained, it will call for a Slave VFD by closing a
relay on the Control Terminal. DXL and LHX Series drives can control up to four auxiliary VFDs.
CAUTION: The relays are rated 0-30 VDC or 120VAC, 0.5 amp.
Direct control of the coil on a magnetic motor starter will likely
cause damage to the relay and the main control printed circuit
board. Use of a secondary control relay, such as an ice cube relay,
may be necessary to control the lag pump motor starter.
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