Operating instructions

25-42 Staging Threshold
Range: Function:
Applica-
tion
depend-
ent
*
[Applica-
tion
depend-
ant]
When adding a fixed speed pump, in order to
prevent an overshoot of pressure, the
variable speed pump ramps down to a lower
speed. When the variable speed pump
reaches the “Staging Speed” the fixed speed
pump is staged on. The Staging Threshold is
used to calculate the speed of the variable
speed pump when the “cut-in point” of the
fixed speed pump occurs. The calculation of
the Staging Threshold is the ratio of
par. 4-11 Motor Speed Low Limit [RPM] or
par. 4-12 Motor Speed Low Limit [Hz], to the
par. 4-13 Motor Speed High Limit [RPM] or
par. 4-14 Motor Speed High Limit [Hz],
expressed in percent.
Staging Threshold must range from
STAGE
%
=
LOW
HIGH
× 100 %
to 100%, where n
LOW
is Motor Speed Low
Limit and n
HIGH
is Motor Speed High Limit.
NOTE
If the set-point is reached after staging before the
variable speed pump reaches its minimum speed - the
system will enter the state closed loop as soon as the
feedback pressure is crossing the set-point.
25-43 Destaging Threshold
Range: Function:
Applica-
tion
depend-
ent
*
[Applica-
tion
depend-
ant]
When removing a fixed speed pump, in order
to prevent an undershoot of pressure, the
variable speed pump ramps up to a higher
speed. When the variable speed pump
reaches the “Destaging Speed” the fixed
speed pump is destaged. The Destaging
Threshold is used to calculate the speed of
the variable speed pump when the destaging
of the fixed speed pump occurs. The calcula-
tion of the Destaging Threshold is the ratio of
par. 4-11 Motor Speed Low Limit [RPM] or
par. 4-12 Motor Speed Low Limit [Hz], to the
par. 4-13 Motor Speed High Limit [RPM] or
par. 4-14 Motor Speed High Limit [Hz],
expressed in percent.
Destaging Threshold must range from
STAGE
% =
LOW
HIGH
× 100 %
to 100%,
where n
LOW
is Motor Speed Low Limit and
n
HIGH
is Motor Speed High Limit.
Parameter Description
VLT
®
HVAC Drive Programming Guide
172 MG.11.CA.02 - VLT
®
is a registered Danfoss trademark
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