Technical Manual Stage Controller MSR
eco
3140
Page 12
SDS -
Suction Pressure Optimization by
Setpoint Shifting with Cold Storage
Controllers
Cold Storage Controllers with EEx-Valves:
When there is a reduced-power requirement, the
setpoint of the compound should be higher than the
set value. If there is a demand for power at a cold
storage location, then it must ensured that the setpoint
shifts down enough to allow the cold storage to reach
its low setpoints.
Within a fixed time interval it will be checked if the
opening rate of the EEx-Valves of the connected
controllers have exceeded a specific limit (
r18
).
If the limit has been exceeded at least at one
cooling position, then the setpoint of the compound
is reduced by a certain value (
r19
).
If the actual value of the alarm probe exceeds the
limit at even one of the cold storage locations, the
setpoint must be lowered. The limit value is based
on the switch-ON point +
d3
.
If the following conditions occur, then the setpoint of
the compound can be raised by a set value, ‚
r19
‘, up
to to the maximum setpoint defined by ‚
r03
‘:
1. At least one EEx-Valve of a cold storage location
is below the limit ‚
r17
‘.
2. No units are running above the upper limit.
3. No cold storage location has exceeded the
safety limit.
Cold Storage Controllers without EEx-Valves:
In these cases, if the actual value of the alarm probe
has exceeded the limit value, (switching point +
d03
), a reduction of the suction pressure setpoint
will be needed. If the actual value is equal to or less
than the limit value, the suction pressure setpoint
can be raised.
The setpoint utilized by the compressor control is
based on the adjusted setpoint, ‚
r01
or
r02
‘, and the
offset values, which are generated by the optimi-
zation process. The entered setpoint is the lowest
possible setpoint.
For each connected cold storage controller with
EEx-Valves two parameters are available at which
this influence can be set up:
d02
.....0=off/no effect, 1=Limitation Temperature,
2=Limitation Temperature
+ Opening Degree
d03
.....Suction Pressure Shift - Temp. Offset
The current increase/decrease values, which have
been produced by this function, can be read at
L31/L32
.
SP-Optimized switching by variable Forerun/
Backrun Runtimes (VBR)
If the difference between setpoint and actual value
is small, the number of switching events should
be reduced. Rapid changes in suction pressure
require a quick delivery of power, which requires
a quick reduction in the power reserve.
This can be achieved by variable switching delays
depending on the actual offset from the setpoint.
This function, ‚
r40
‘, is located on the Setpoint
Page.
The forerun/backrun times will be activated if the
suction pressure goes beyond the hysteresis
range. Above and below the hysteresis range are
definable areas (
VBR Forerun Range
r41
respective VBR Backrun Range
r42
). If the
suction pressure actual value moves within this
areas, the forerun/backrun times will be varied
within the ranges set by
r43
(
VBR Forerun/
Backrun Time min
) and
r44
(
VBR Forerun/
Backrun Time max
).
The bigger the difference between actual value
and setpoint, the shorter the time delay. If the
actual value leaves the set range, always the
smallest set delay value will be used.
If the elapsed time increases the current calcula-
ted time, the function begins to switch.
For information
L34
(
Remaining time of Forerun/
Backrun
) shows the current calculated delay
time.
Forerun/Backrun
Time max.
Forerun/Backrun
Time min.
C
ur
re
nt
s
et
po
in
t
(e
.g
. 3
.0
b
ar
)
Backrun
(switch off)
Delay
Forerun
(switch off)
Delay
Backrun Area
Forerun Area
Hysteresis
Range
Suction Pressure
Machines with Feedback (SP, Motor 1-4)
To detect the real state of a machine, the safety chain
can be checked using a digital input, which has a
feedback function, (
h31
...
h34
).
The controller switches a machine on and waits for a
feedback signal while power is being applied to the
digital input. If no feedback is detected, the machine
will be switched off and a different machine will be
selected.
‚
r21
‘ can be used to set the waiting time. If the swit-
ching of a machine is unsuccessful, a new starting
attempt can be initiated after an automatically
calculated time delay.
Switching Behaviour of the Stage Relays
The switching behaviour can be set to active (relay
switches on) or passive (relay switches off) with the
parameters (
h61
...
h68, SP)
and (
h81...h88, HP
).
With the setting '1' the stage will be inverted, with
'0' the stage switches normally.
Load Limitation (SP)
A load limitation can be established for each of the 4
digital inputs. This can be used during peak opera-
tion periods. Two inputs can be assigned their own
maximum number (
r11
...
r12
) of running machines to
provide more opportunity for energy savings.
Operating Mode of the Motors (Manual/Auto)
Each motor can be set to manual „ON/OFF“ operation
via ‚
r61-r68
‘ for
SP
, and ‚
d61-d68
‘ for
HP
.
Default „ON/OFF“ operation is set to „Auto“.
Second Setpoint (Ex. Night Operation)
Alternate setpoints can be established for energy
savings. ‚
r01
‘ can be established as a day setpoint,
and ‚
r02
‘ for night time. These can be alternated via
internal timer settings ‚
P21
‘/‘
P22
‘, or any digital input
‚
h31
...
h34
‘, setting
dnl
or
dnh
.
If one of the DI inputs is configured for day/night
switching and it has been activated,, the 2nd
setpoint is active all time and cannot be changed
by the internal timer.
If you want to use external switching only, please
set '
P21
' and '
P22
' to „oFF“.
For night operation, the high pressure controller
has a night offset (
d10
) and additionally a night
limitation (
d11
) for the analogue output.