61
ENG
µchiller +0300053EN rel. 2.2 - 14.12.2021
Functions
5.5.3 BLDC compressor start-up
Chiller manages the start-up of BLDC compressors in accordance with the manufacturer’s specifi cations: on starting, the com-
pressor is brought to start- up speed and kept at that speed, irrespective of the control request, for the entire minimum on time.
At the end of this period, the speed is modulated by the controller, based on:
• request;
• position of the working point in relation to the compressor envelope (see par. "Prevention actions").
Note: if at start-up the diff erential pressure is greater than the maximum allowed start-up threshold, the compressor remains
on call awaiting the pressure to drop below the threshold. If after 5 minutes the compressor has not yet started, a specifi c alarm
will be activated (A43/A76). However, this alarm still allows the other compressors to start.
User Code Description Def Min Max UOM
M P021 Max. deltaP at start-up 900.0 0.0 2000.0 kPa
5.5.4 BLDC oil recovery
When the refrigerant gas speed in the circuit is below the value required to entrain the oil, operation periodically needs to be set
to a suffi cient value to guarantee oil return to the compressor crankcase.
The function forces an increase in BLDC compressor capacity for a specifi c time, when the circuit has remained at low load (par.
P007) for a minimum time (par. P008).
User Code Description Def Min Max UOM
M P018 Enable oil recovery - 0/1=No/Yes 001-
M P007 Oil recovery: min speed for activation 35.0 0.0 999.9 rps
M P008 Oil recovery: comp. operating time at low speed 15 0 999 min
M P009 Oil recovery: force comp. speed time 3 0 999 min
M P010 Oil recovery: force comp. speed value 50.0 0.0 999.9 rps
5.5.5 Tandem BLDC oil equalisation
A solenoid valve is activated to take the oil from the crankcase overfl ow on each compressor and put it back in circulation (for
example, at the inlet to the common manifold). If the function is enabled, when the fi xed speed compressor starts, the sole-
noid valve is activated for an initial time (par. P011), and then cyclically for a time (par. P012), with a pause that increases over time
from the minimum value (par. P013) to the maximum value (par. P014) in the specifi ed time (par. P015).
User Code Description Def Min Max UOM
M P017 Enable oil recovery - 0/1=No/Yes 001-
M P011 Oil recovery: min speed for activation 30 0 999 s
M P012 Oil recovery: comp. operating time at low speed 3 0 999 s
M P013 Oil recovery: force comp. speed time 1 0 999 min
M P014 Oil recovery: force comp. speed value 15 0 999 min
M P015 Equalizzazione olio: tempo incremento elettrovalvola chiusa 20 0 999 min
5.5.6 Compressors with capacity control (Legacy model only)
For Legacy models, compressors can be capacity-controlled in the compressor plus valve confi guration, on a maximum of two
circuits. For compressors with capacity control, the FIFO or timed rotation logic will refer to the circuit and not to the compressor
valves.
Example: if circuit 1 starts when power returns, compressor 1 starts at part capacity, then the valve is managed as the second
step, so that the compressor works at the highest effi ciency. If less capacity is needed, fi rst the valve that manages compressor
capacity will be deactivated and then the compressor itself. There is no rotation between compressor and valve. When capacity
is needed again, the second circuit with compressor 2 will be activated and, subsequently, if required, the corresponding valve.
On deactivation, the valve will be managed fi rst, and only then the compressor.
User Code Description Def Min Max UOM
M F027 Enable compressor capacity control 0/1=No/Yes 001-
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