GEA GSC TP Manuel utilisateur
GSC TP
Sequence Control for Packages
Operating Manual (Translation of the original text)
E_301510_2
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No part of this publication may be copied or pub-
lished by means of printing, photocopying, microfilm
or otherwise without prior written consent of
•GEA Refrigeration Germany GmbH
herein after called manufacturer. This restriction
also applies to the corresponding drawings and dia-
grams.
LEGAL NOTICE
This documentation has been written in all con-
science. However, the manufacturer cannot be held
responsible, neither for any errors occurring in this
documentation nor for their consequences.
Operating Manual | Sequence Control for Packages
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SYMBOLS USED IN THIS MANUAL
Danger!
Stands for an immediate danger which
leads to heavy physical injuries or to
the death.
Warning!
Stands for a possibly dangerous situa-
tion which leads to heavy physical
injuries or to the death.
Caution!
Stands for a possibly dangerous situa-
tion which could lead to light physical
injuries or to damages to property.
Hint!
Stands for an important tip whose
attention is important for the designa-
ted use and function of the device.
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TABLE OF CONTENTS
1 PARAMETERS 9
1.1 Explanation of the parameters of local control 9
1.1.1 Screw compressor capacity control 9
1.1.2 Reciprocating compressor capacity control 11
1.2 Explanation of the parameters of sequence control options 12
2 EXAMPLES FOR THE SEQUENCE CONTROL OF PACKAGES 14
2.1 Conditions for capacity increase 15
2.2 Conditions for capacity decrease 16
2.3 Variable capacity demand - example 1 17
2.4 Variable capacity demand - example 2 18
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TABLE OF FIGURES
fig. 1 Hysteresis, Neutral Zone 10
fig. 2 Calculating the step time 12
fig. 3 14
fig. 4 Conditions for capacity increase 15
fig. 5 Conditions for capacity decrease 16
fig. 6 Variable capacity demand - example 1 17
fig. 7 Variable capacity demand - example 2 18
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1 PARAMETERS
This chapter presents the parameters relevant for sequence control system.
The sequence control for packages is set up so that the local control for each unit is active. The sequence mod-
ule overrides the local control on certain units in relation to the current running condition. These units are then
not controlled by their setpoints and process values but by the sequence module.
1.1 Explanation of the parameters of local control
Operation mode Required operation mode
Operation modes 0, 1, 2, 5 and 9 are not permitted.
Process value Process value that should be controlled, e.g. suction pressure,
external temperature, discharge pressure
Setpoint °C Setpoint for capacity control
Neutral zone K
As soon as the process value is within this zone, the compressor
capacity is not changed. Exception is if a capacity limitation
becomes active, then the controller can change the capacity. The
zone lies symmetric around the setpoint.
The value must be less than the value for the proportional zone (see
1.1.2 "Capacity control of reciprocating compressors").
Auto start delay secs Initiated by process value rising above Neutral Zone and compres-
sor not running.
Auto stop delay secs
The auto stop delay occurs only when the relevant compressor in
the sequence is active.
The auto stop delay is initiated by process value falling below Neu-
tral Zone and compressor running with Part Load or less
capacity and only one compressor in the sequence is active.
1.1.1 Screw compressor capacity control
Hysteresis K
Area at the boundary of the neutral zone where in dependence of
the direction of the process value change the capacity control does
not change the compressor capacity.
Load pulse secs Pulse time for capacity increase.
Unload pulse secs Pulse time for capacity decrease.
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Parameters
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Pause secs Pause time between pulses.
Auto stop position %
As soon as the control slide has reached this value or is below this
value the "Auto stop delay" will start (stand alone operation). In
sequence operation the control slide is stopped at this position and
the compressor is allowed to stop if it is allowed by the sequence
module.
fig.1: Hysteresis, Neutral Zone
PV Process value
SP Setpoint
NZ Neutral zone
HYS Hysteresis
A Time characteristic of process value
B Time characteristic of the 3-step-controller outputs
C Time characteristic of the pulse generator
D Time character of the pulsed outputs to the capacity control solenoid valves
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Table des matières
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