Xylem HYDROVAR HV 4.150 / 4.185 / 4.220 - Manual (Page 10)

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3.2.3 Cascade Serial / Synchronous (not for SINGLE version)
In these modes various combinations among the versions BASIC and MASTER Inverter are
possible.
In general each of the pumps needs to be equipped with a HYDROVAR unit. All the units
are connected via the RS485 interface and communicate via the standard MODBUS-
protocol (9600 Baud, RTU, N81).
To realise a fully controlled system at least one MASTER Inverter is needed, the remaining
pumps could be fitted just with a BASIC Inverter.
The controller in the MASTER Inverter is continuously in communication with all the BASIC
Inverters. All failures are indicated on the MASTER including the date and time.
All the control is done by the MASTER Inverter including automatic change over of the lag
pumps to provide even wear and achieve even operating hours.
If the control card of a MASTER Inverter fails, each of the BASIC Inverters can be manually
started by an external switch (manual operation) in order to ensure an emergency
operation of the system.
Application Example
Each pump of the system (up to 8 pumps) is equipped with a HYDROVAR unit (at least one
MASTER Inverter and remaining ones can be BASIC Inverters). All units are connected via
the serial interface (RS485).
The combination of the different HYDROVAR units which are used in a multi-pump-system
depends on the system requirements (i.e. in a 6 pump system 2 MASTER Inverters can be
used due to reliability reasons and 4 BASIC Inverters without control card – or just any
other combination).
Minimum requirement: 1 MASTER Inverter and the other pumps equipped with BASIC
Inverters