Danfoss MCO 101 Manual

Danfoss MCO 101 Manual Manual pdf 30 page image

Delay (27-24) time. This repeats for all of the fixed-speed pumps. This leaves only one variable speed pump running. If the system demand continuesto drop, the system will enter sleep mode.5.2.8 Override Staging /De-stagingNormal staging and de-staging handles most of the situations in typical applications. However, sometimes it is necessary to respond rapidly to changesin system feedback pressure. In these cases, the cascade controller is equipped to immediately stage and de-stage pumps in response to large changessystem demand.Staging:When the system pressure drops by more than the Override Limit (27-21), the cascade controller will immediately stage on a pump to meet the demandfor more flow.If the system pressure continues to stay below the Override Limit (27-21) for the Override Hold Time (27-25) time, the cascade controller will then stageon the next pump. This repeats until all of the pumps are on or until the system pressure drops below the override limit.De-staging:When the system pressure increases rapidly above the Override Limit (27-21), the cascade controller will immediately de-stage a pump to try to reducethe pressure.If the system pressure continues to stay above the Override Limit (27-21) for the Override Hold Time (27-25) time, the cascade controller will de-stageanother pump. This will repeat until only the lead pump is left on or until the pressure stabilizes.The Override Limit parameter 27-21 is set as a % of the maximum reference. It defines a point above and below the system setpoint where overridestaging and de-staging will occur.5.2.9 Minimum Speed De-stagingTo reduce emergency usage, the cascade controller will de-stage a pump if the lead pump is running at minimum speed for Min. Speed De-stage Delay(27-27).5.2.10 Fixed speed only operationFixed Speed only operation is a feature designed to keep critical systems operating in the rare event that all of the variable speed pumps are unavailableto the cascade controller. In this situation, the cascade controller will attempt to maintain system pressure by turning fixed speed pumps on and off.Staging:If all the variable speed pumps are unavailable, and the system pressure drops below the Fixed Speed Only Operating Range (27-22) for the StagingDelay (27-23) time, then a fixed speed pump will be turned on. This repeats until all of the pumps are on.De-staging:If all of the variable speed pumps are unavailable and the system pressure goes above the Fixed Speed Only Operating Range (27-22) for the De-stageDelay (27-24) time, a fixed-speed pump will be turned off. This repeats until all of the pumps are off.5 Cascade Controller FeaturesExtended and Advanced Cascade ControllerOption5-4 MI.38.C2.22 - VLT® is a registered Danfoss trademark5