F
Operating instructions
cod. 1592001330
1592001330 XC642C GB r1.0 07.06.2004.doc
rel. 1.0
Pa. 14 / 21
15.2 PROPORTIONAL BAND
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 compr. 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:
Proportional band control with four steps
In this example:
oA1 = cMP; oA2 = StP; oA3 = StP; oA4 = StP:
4
steps
rty = Pb
proportional band regulation
FdLy = no
“don” delay at first call not enabled.
dLF= no
“doF” delay at first call not enabled.
Relay 1 - Compressor Relay valve 1 (25%)
Relay valve 1 (50%)
Relay valve 1 (75%)
25%
ON
ON
OFF
OFF
50%
ON
OFF
ON
OFF
75%
ON
OFF
OFF
ON
100%
ON
OFF
OFF
OFF
oA1(Compressor)
oA2(25%)
oA3(50%)
oA4(75%)
SET
Set+Pbd/2
Set-Pbd/2
ZIC
Set+Pbd/4
Set-Pbd/4
don
doF
COMPRESSOR AT 100%
ALL LOADS ARE ACTIVE
