Danfoss VLT HVAC Series Programming Manual page 270

3 Parameter Description
25-51 Alternation Event
Option:
[0] * External
3
[1] Alternation Time Interval
[2] Sleep Mode
[3] Predefined Time
25-52 Alternation Time Interval
Range:
24 h* [1 - 999 h]
25-53 Alternation Timer Value
Range:
0 N/A* [0 - 0 N/A]
25-54 Alternation Predefined Time
Range:
0 N/A* [0 - 0 N/A]
25-55 Alternate if Load < 50%
Option:
[0] Disabled
[1] * Enabled
3-246
Function:
This parameter is only active if the options
been selected in par.25-50 Lead Pump Alternation
of lead pump takes place every time the event occurs.
Alternation takes place when a signal is applied to one of the digital inputs on the terminal strip and
Lead Pump Alternation
this input has been assigned to
Alternation takes place every time par.25-52
Alternation takes place each time the lead pump goes into sleep mode. par.20-23
Sleep Mode
be set to [1] or an external signal applied for this function.
Alternation takes place at a defined time of the day. If par.25-54
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).
Function:
Alternation Time Interval
If [1] option in par.25-51
the variable speed pump takes place every time the Alternation Time Interval expires (can be
checked out in par.25-53 Alternation Timer Value
Function:
Readout parameter for the Alternation Time Interval value set in par.25-52
val
.
Function:
Predefined Time
If option [3] in par.25-51
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).
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).
N RUNNING
Capacity
= × 100 %
N TOTAL
For the basic cascade controller, all pumps are equal size.
The lead pump alternation will take place at any pump capacity.
The lead pump function will be alternated only if the numbers of pumps running are providing less
than 50% of total pump capacity.
MG.11.C6.22 - VLT ® is a registered Danfoss trademark
VLT ® HVAC Drive Programming Guide
At Command [2] or At Staging or Command
. If an alternation event is selected, the alternation
par. 5-1*, Digital Inputs
[121] in
Alternation Time Interval expires.
Alternation Predefined Time
Alternation Event
is selected, the alternation of
).
Alternation Time Inter-
Alternation Event
is selected, the variable speed pump
[3] have
.
Setpoint 3 must
is set,