Danfoss MCO 101 Manual page 35

Extended and Advanced Cascade Controller
Option
27-22 Fixed Speed Only Operating Range
Range:
P27-20* [P27-20 - P27-21]
27-23 Staging Delay
Range:
15 s* [0–3000 s]
27-24 De-staging Delay
Range:
15 s* [0–3000 s]
27-25 Override Hold Time
Range:
10 s* [0–300 s]
27-27 Min-Speed De-stage Delay
Range:
15 s* [0–300 s]
Function:
Fixed Speed Only Operating Range is the allowed offset from the setpoint before a pump may be
added or removed when there are no operational variable speed pumps. The system must be outside
this limit for the time specified in P27-23 (Staging Delay) or P27-24 (De-staging Delay) before a
cascade operation may take place. The value is entered as a % of Max Reference. When there are
no operational variable speed pumps, the system will try to maintain control with the remaining
fixed speed pumps.
Function:
Staging Delay is the time that the system feedback must remain below the operating range before
a pump may be turned on. If the system is operating with at least one variable speed pump available,
the Normal Operating Range (P27-20) is used. If there are no variable speed pumps available, the
Fixed Speed Only Operating Range (P27-22) is used.
Function:
De-staging Delay is the time that the system feedback must remain above the operating range
before a pump may be turned off. If the system is operating with at least one variable speed pump
available, the Normal Operating Range (P27-20) is used. If there are no variable speed pumps
available, the Fixed Speed Only Operating Range (P27-22) is used.
Function:
Override Hold Time is the minimum time that must elapse after a stage or de-stage before a stage
or de-stage may take place due to the system exceeding the override limit (P27-21). The override
hold time is designed to allow the system to stabilize after a pump is turned on or off. If this delay
is not long enough, the transients caused by turning a pump on or off may cause the system to add
or remove another pump when it should not.
Function:
Min-Speed De-stage Delay is the time that the lead pump must be running at minimum speed while
the system feedback is still inside the normal operating range before a pump will be turned off to
save energy. Energy savings may be realized by turning off a pump if the variable speed pumps are
operating at minimum speed, with the feedback still in band. Under these conditions, a pump may
be turned off and the system will still be able to maintain control. The pumps that remain on will
begin operating more efficiently.
®
MI.38.C2.22 - VLT is a registered Danfoss trademark
6 How to Program
6
6-5