Operating time before time depending
load replacement
Load replacement depending on time is mainly
used in the field of refrigeration technology to ba-
lance the use of the connected compressors. If only
some of the outputs are continuously active, out-
puts that have not yet been activated will be used.
This parameter determines the time to elapse be-
fore outputs are changed for the first time. If there
are multiple bypass groups defined with parameter
the load replacement affects entire groups.
Time scale for parameter
Parameter
sets the time scale for parameter
(seconds or minutes).
Active measuring input
This parameter selects either temperature or
pressure measuring. Deactivated sensors can be
disconnected; their measuring input causes no
error message. At the same time the scale of the
main display is set to either “°C” or “bar”.
Refrigerant
Selection of the used refrigerant in the plant.
Time-dependent load replacement
This parameter either activates or deactivates time-
dependent load replacement to balance the use of
the connected compressors. The replacement
takes place after the operating time set with
parameters
and
.
Sequential operation mode
This parameter either activates or deactivates the
sequential operation mode. If this mode is activated
different compressors or bypass-groups will be ac-
tivated or deactivated (if possible) at each change
of output stage to ensure an even load of the
compressors.
Concerning the switching of the compressors or
bypass-groups the following applies:
If several compressors or bypass-groups are acti-
vated the first started unit will be deactivated first.
If several units are deactivated the first stopped unit
will be activated first.
If in sequential operation mode the connections of
the units to the respective output stage is ineffec-
tive. The control prevents the switching of valves if
the compressor has not started and assures the
simultaneous switch-off of valves when the com-
pressor is switched off. The minimum action times
(parameters
-
) concerning valves will be
adjusted to the times of the respective
compressors.
Operating mode
If a sequential operation mode or the time-depen-
dent load replacement is activated with parameter
and
, parameter
selects which
outputs are involved in this mode.
Additionally it is possible to define pairs of outputs
that work as bypass-groups. In this case the acti-
vation of the valve output leads to a smaller cooling
performance. In the bypass-groups there is a
standard linkage of the outputs, i.e.
K1=compressor,
K2=bypass,
K3=compressor,
K4=bypass,
K5=compressor,
K6=bypass.
Bypass-groups with an inverted valve output are
intended for plants where the bypass is switched on
together with the compressor and switched off
together with the valve output.
A special function (
=12) allows the operation of
two compressors together with a common bypass
with
K1+K3=compressor,
K2=bypass.
In this case K4 becomes inactive, because
parameters P3 and P14 are reserved. A further
special function (
=13) is intended for the
operation with double bypass-groups with
K1=compressor,
K2+K3=bypass,
K4=compressor,
K5+K6=bypass.
Not that the sequential operation mode and the
time-dependent load replacement are effective
independently of each other if activated with para-
meters
and
. If bypass operation mode is
selected, the required valves are determined
summarily in the control program.
If the respective setting requires several bypass
valves to be switched on, the output with the
highest number will be switched on first.
Summary of Contents for ST710-PWHVR.126
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