27-22 Fixed Speed Only Operating Range
Range:
Function:
P27-20*
[P27-20 - P27-21]
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.
27-23 Staging Delay
Range:
Function:
15 s*
[0–3000 s]
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.
27-24 De-staging Delay
Range:
Function:
15 s*
[0–3000 s]
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.
27-25 Override Hold Time
Range:
Function:
10 s*
[0–300 s]
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.
27-27 Min-Speed De-stage Delay
Range:
Function:
15 s*
[0–300 s]
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.
Extended and Advanced Cascade Controller
Option
6 How to Program
MI.38.C2.22 - VLT
®
is a registered Danfoss trademark
6-5
6
