Xylem HYDROVAR (HV2.1 - 3.45) - Manual (Page 68)

68
Examples
Booster unit
Problem: no stop of the HYDROVAR
Parts to check Solution
• existing demand
• non return valve is not closed
• pre charge pressure in the pressure tank
• no correct settings of WINDOW and
RAMPHYSTERESIS
• shut down RAMP too slow
• suction line too long
• check pipes and valves
• change non return valve
• adjust according the diagram
• set WINDOW (ca.10%) and
RAMPHYSTERESIS (80-50%)
• set RAMP 2 to 4...15 sec.
• the MINIMUM FREQUENCY should be
activated for pressure increase at 0 demand
Control on constant flow
Problem: control fluctuations
Parts to check Solution
control characteristics are set to low
enlarger WINDOW and RAMPHYSTERESIS to
99% to control with RAMP 3 and 4
Circulating pump
Problem: oscillation of the motor speed
Parts to check Solution
control settings too fast
• increase RAMP 3 and 4: 100...200sec
• WINDOW (ca.20%) and
RAMPHYSTERESIS (ca.99%)
Problem: ACTUAL VALUE can't be hold
Parts to check Solution
Ramphysteresis too big RAMPHYSTERESIS: 90-99%
Submersible pumps
Problem: motor cables are too long
Solution: reduce SWITCHING FREQUENCY, BOOST: 10-20%
General
Problem: pressure fluctuations, analogue signal not constant
Solution:
• check cables and connection of the screen
• check earth connection of the Transmitter
• use screened cables