After a time delay, the relay for the fixed speed pump cutsin (staged) and this pump becomes the new lead pump.The new lead pump ramps up to maximum speed andthen down to minimum speed. When ramping down andreaching the staging frequency, the old lead pump is nowcut in (staged) on the mains as the new fixed speed pump.If the lead pump has been running at minimum frequency(fmin) for a programmed amount of time, with a fixedspeed pump running, the lead pump contributes little tothe system. When the programmed value of the timerexpires, the lead pump is removed, avoiding a watercirculation problem.6.1.10 System Status and OperationIf the lead pump goes into sleep mode, the function isdisplayed in the LCP. It is possible to alternate the leadpump on a Sleep Mode condition.When the cascade controller is enabled, the operationstatus for each pump and the cascade controller isdisplayed on the LCP. Information displayed includes:• Pumps Status is a read out of the status for therelays assigned to each pump. The display showspumps that are:- Disabled- Off- Running on the mains/motor starter• Cascade Status is a read out of the status for thecascade controller. The display shows thefollowing conditions:- Cascade controller is disabled- All pumps are off- An emergency has stopped all thepumps- All pumps are running- Fixed speed pumps are being staged/destaged- Lead pump alternation is occurring.• De-stage at no-flow ensures that all fixed speedpumps are stopped individually until the no-flowstatus disappears.6.1.11 Fixed Variable Speed Pump WiringDiagramL1/L2/L3 L1/L2/L3 L1/L2/L3Power SectionRELAY 1RELAY 2130BA376.10Illustration 6.9 Fixed Variable Speed Pump Wiring Diagram6.1.12 Lead Pump Alternation WiringDiagram130BA377.13L1/L2/L3FCL1/L2/L3 L1/L2/L3k3k2k3k1K2K1K1 K1K4 K3K4K3R1R2Illustration 6.10 Lead Pump Alternation Wiring DiagramEvery pump must be connected to 2 contactors (K1/K2 andK3/K4) with a mechanical interlock. Apply thermal relays orother motor protection devices according to localregulation and/or individual demands.• Relay 1 (R1) and Relay 2 (R2) are the built-inrelays in the frequency converter.• When all relays are de-energised, the first built inrelay to be energised cuts in the contactorcorresponding to the pump controlled by therelay.Application Examples Design GuideMG16C202 Danfoss A/S © Rev. 05/2014 All rights reserved. 1656 6
