12.12 Wiring Configuration for a FixedVariable Speed PumpL1/L2/L3 L1/L2/L3 L1/L2/L3Power SectionRELAY 1RELAY 2130BA376.10Illustration 12.7 Fixed Variable Speed Pump Wiring Diagram12.13 Wiring Configuration for Lead PumpAlternation130BA377.13L1/L2/L3FCL1/L2/L3 L1/L2/L3k3k2k3k1K2K1K1 K1K4 K3K4K3R1R2Illustration 12.8 Lead Pump Alternation Wiring Diagram.Every pump must be connected to 2 contactors (K1/K2 andK3/K4) with a mechanical interlock. Thermal relays or othermotor overload protection devices must be appliedaccording to local regulation and/or individual demands.• Relay 1 (R1) and relay 2 (R2) are the built-in relaysin the drive.• When all relays are de-energized, the 1st built-inrelay that is energized cuts in the contactorcorresponding to the pump controlled by therelay. For example, relay 1 cuts in contactor K1,which becomes the lead pump.• K1 blocks for K2 via the mechanical interlock,preventing mains from being connected to theoutput of the drive (via K1).• Auxiliary break contact on K1 prevents K3 fromcutting in.• Relay 2 controls contactor K4 for on/off control ofthe fixed-speed pump.• At alternation, both relays de-energize and nowrelay 2 is energized as the 1st relay.For a detailed description of commissioning for mixedpump and master/slave applications, refer to VLT® CascadeController Options MCO 101/102 Operating Instructions.Application Examples VLT® AQUA Drive FC 202118 Danfoss A/S © 05/2017 All rights reserved. MG22B1021212
