1592001850 XC660D GB r3.4 04.09.2017.docx XC660D 34/55
18. Even Capacity Compressors (CtyP = Spo)
18.1 Compressors With Same Capacity – Dead band control
This regulation is applied both to the circuit 1 and the circuit 2.
The neutral zone (Pbd) is symmetrical compared to the target set point, with extremes: set+Pbd/2
... set-Pbd/2. If the pressure (temperature) is inside this zone the controller maintains the same
number of loads switched on and off, without changing anything.
When the pressure (temperature) go out from the zone, regulation starts. If the pressure is greater
than SET+Pbd/2, the loads are switching on with timing given by parameters: don and doF.
A load is turned on only if his safety times onon, oFon, donF are over.
Regulation stops when the pressure (temperature) comes back into the neutral zone.
In the following a simplify example that explains the regulation in neutral zone for compressor
homogeneous with 1 step for each compressors. The safety times onon, oFon and donF are not
considered. In the real regulation any load is entered or turned off only if these times are over.
Ex. Dead band control, compressors with same capacities, 1 step for each compressor.
In this example:
oA1 = cPr1; oA2 = cPr1; oA3 = cPr1; oA4 =nu; oA5 = nu number of compressors
CtyP = SPo homogeneous compressors;
Sty = yES rotation
FdLy = no “don” delay not enabled at first calling after an equilibrium condition.
dLF = no “doF” delay not enabled at first calling after an equilibrium condition.
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