NOTICE D’INSTRUCTIONS GENERALE POUR
COFFRETS ET ARMOIRES ELECTRIQUES
V3.0
Page 42 / 51
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Compressors manufacturers impose a limited number of start in one hour. To meet this
manufacturer recommendation, control panels are equiped with « short cycle timers » either by
electrical components feature as by the automation system (PLC, regulator).
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When all the securities are enabled, compressors are ready to start if the short cycle timers are
ready too.
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In manual or pressostatic operating mode, there are two kinds of short cycle timers depending on
the installation:
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Only one compressor :
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The short cycle timer is used at the start of the compressor, it means that the timer is
counting when the compressors starts. If the compressor stops after timer setup time
(around 6 mn), the compressor can start again immediately. If the compressor stops
before the end of the timer, it stays stopped until the timer preset time is reached.
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This operating mode allows to restart immediately, which is very important when the
installation only has one compressor. System reactivity is optimum.
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Multiple Compressors :
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The short cycle timer is used at the stop of the compressor. When the compressor stops,
the timer starts to count and the compressor will stay stopped during all the setup time
of the timer (according to compressors manufacturers datas).
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This working principle is different because in case of power shut down, timers at the
start of compressors will be at ON when the power comes back, and it could risk to
enable all compressors to start simultaneously.
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Reminder : All the timers present in the control panel must be set before
starting the installation.
