Xylem HYDROVAR HV 4.150 / 4.185 / 4.220 User Manual
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3.2.4 Cascade Relay (not for SINGLE version)
One pump is fitted with a HYDROVAR MASTER Inverter and up to 5 slave pumps can be
switched ON and OFF on demand. For this purpose an additional relay card including 5
relays is attached to the MASTER Inverter.
However an external switchboard is needed for all the motor relays as the relays in the
HYDROVAR are not able to switch the pumps directly (just used as control contacts).
Also an automatic change over of the fixed speed pumps to provide even wear and achieve
even operating hours is possible in this mode.
This configuration is a cost effective alternative compared with other solutions using VFD’s
on each pump, but in any case care has to be taken due to the lower reliability of such a
system.
Application example
Booster sets up to 6 pumps where only one pump is speed controlled by the HYDROVAR
and the others are fixed speed (1 HYDROVAR MASTER Inverter+5 fixed speed).