65
ENG
µchiller +0300053EN rel. 2.2 - 14.12.2021
Functions
Low di erential pressure prevention (zone 7)
Device Description
BLDC compressor 1. Decrease the rate of capacity reduction.
2. Increase capacity
Tandem on-off compressors -
ExV valve Variable MOP
Fan Increase condensing pressure set point/decrease evaporation pressure setpoint
Low condensing pressure prevention (zone 8)
Device Description
BLDC compressor 1. Decrease the rate of capacity reduction.
2. Increase capacity
Tandem on-off compressors -
ExV valve -
Fan -
5.8 Compressor alarms
If abnormal conditions occur and the prevention actions are not eff ective, the compressor will be shut down so as to avoid
damage to the compressor itself or other unit components, i.e. the control algorithm stops the compressors and closes the
expansion valve.
Compressor shutdown
The compressors will be available again after the:
• minimum compressor off time (par. C013);
• minimum time between consecutive compressor starts (par. C014).
User Code Description Def Min Max UOM
M C013 Min compressor off time 60 30 999 s
M C014 Min time between consecutive compressor starts 360 300 999 s
Compressor delay at start-up/in operatio
Compressor start-up is a critical phase. Chiller thus manages certain alarms diff erently, in order to switch smoothly from start-
up to normal, steady operation. These alarms are:
• low diff erential pressure;
• out of envelope alarm.
There are thus two delays for these alarms:
• delay at start-up;
• delay in operation.
The alarm condition is ignored when the compressor is off and during the start-up phase. When the unit reaches steady opera-
tion, the condition causes the corresponding alarm once the delay has elapsed.
Behaviour will thus be as follows
300053_061_R01
D2
D1
ALS
ALC
Comp
D2
Key
Comp Compressor status
ALC Status of the alarm condition
ALS Alarm signal
D1 Alarm disabling from compressor start-up
D2 Alarm delay in operation
t Time
Fig. 5.p
5.9 Power+ Speed drive
When the unit is fi tted with a BLDC compressor, this is controlled by the Power+ speed drive, connected to the FBus serial port
on Chiller via the Modbus circuit 1 protocol with a baud rate of 19200 bps. Use a specifi c cable for RS485 (AWG20-22 with 1½
twisted pair plus shield). See the Power+ instruction manual +0300048EN.
To Next Page
Loading...
