Danfoss VLT HVAC Series User Manual

25-51 Alternation Event
Option: Function:
This parameter is only active if the options At Command [2] or At Staging or Command [3] have
been selected in par.25-50
Lead Pump Alternation . If an alternation event is selected, the alternation
of lead pump takes place every time the event occurs.
[0] * External Alternation takes place when a signal is applied to one of the digital inputs on the terminal strip and
this input has been assigned to
Lead Pump Alternation [121] in par. 5-1*, Digital Inputs .
[1] Alternation Time Interval Alternation takes place every time par.25-52
Alternation Time Interval expires.
[2] Sleep Mode Alternation takes place each time the lead pump goes into sleep mode. par.20-23
Setpoint 3 must
be set to
Sleep Mode [1] or an external signal applied for this function.
[3] Predefined Time Alternation takes place at a defined time of the day. If par.25-54
Alternation Predefined Time is set,
the alternation is carried out every day at the specified time. Default time is midnight (00:00 or
12:00 AM depending on the time format).
25-52 Alternation Time Interval
Range: Function:
24 h* [1 - 999 h] If Alternation Time Interval [1] option in par.25-51 Alternation Event is selected, the alternation of
the variable speed pump takes place every time the Alternation Time Interval expires (can be
checked out in par.25-53
Alternation Timer Value ).
25-53 Alternation Timer Value
Range: Function:
0 N/A* [0 - 0 N/A] Readout parameter for the Alternation Time Interval value set in par.25-52 Alternation Time Inter-
val
.
25-54 Alternation Predefined Time
Range: Function:
0 N/A* [0 - 0 N/A] If option Predefined Time [3] in par.25-51 Alternation Event is selected, the variable speed pump
alternation is carried out every day at the specified time set in Alternation Predefined Time. Default
time is midnight (00:00 or 12:00 AM depending on the time format).
25-55 Alternate if Load < 50%
Option: Function:
If Alternation If Capacity <50% is enabled, the pump alternation can only occurs if the capacity is
equal to or below 50%. The capacity calculation is the ratio of running pumps (including the variable
speed pump) to the total number of available pumps (including variable speed pump, but not those
interlocked).
Capacity =
N
RUNNING
N
TOTAL
× 100%
For the basic cascade controller, all pumps are equal size.
[0] Disabled The lead pump alternation will take place at any pump capacity.
[1] * Enabled The lead pump function will be alternated only if the numbers of pumps running are providing less
than 50% of total pump capacity.
3 Parameter Description VLT
®
HVAC Drive Programming Guide
3-246 MG.11.C6.22 - VLT
®
is a registered Danfoss trademark
3

Danfoss VLT HVAC Series Specifications

General

Protection Features	Overcurrent, Overvoltage, Undervoltage, Overtemperature, Short circuit
Communication Interfaces	Profibus, Ethernet
Cooling Method	Forced convection
Ambient Temperature	-10°C to +40°C
Enclosure Rating	IP20, IP21, IP55
Output Voltage	0 - 100% of supply voltage