Operating instructions
cod. 1592001300
1592001300 XC440C gb r1.0 07.06.2004.doc
rel. 1.0
Page
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13.2 Proportional Band – for compressors or fans
The regulation band (Pbd) is divided into as many parts as there are stages according to the
following formula:
# step = oAi = CPr or StP (number of compressors or steps).
The numbers of stages switched ON is proportional to the value of the input signal: when this
distances itself from the target set point and enters the various bands, the compressors are
switched ON, to be then turned OFF when the signal brings near the set point.
In this way if the pressure is greater than regulation band, all the compressors are on, if the
pressure (temperature) is lower than the regulation band all the compressors are off.
Naturally also for this regulations all the delays (don and doF) safety times (onon, oFon and
donF) are valid.
Regulation according to the running hours
The algorithm switch on and off the loads according to the running hours of each load. In this
way the running hours are balanced.
Example
oA1 = cPr; oA2 = cPr; oA3 = cPr; oA4 = cPr: 4 compressors
CtyP = SPo homogeneous
compressors.
rty = Pb
proportional band regulation
Sty = yES
rotation
FdLy = no
“don” delay at first call not enabled.
dLF= no
“doF” delay at first call not enabled.
&
&
&
&
6(7
S et+Pbd/2
S et-Pbd/2
=,&
S et+Pbd/4
S et-Pbd/4
GRQ
GR)
A LL LO AD S O N
A LL LO AD S O FF
This draw highlights the doF time: the loads are in fact turned off only when the doF time is
over.
