µRack
Cod. CAREL +03P220431 rel. 0.0 del 08/09/05 - preliminary version
12
4.6. Manually enable/disable the compressors
A compressor can be temporarily disabled from the control sequence. This function is very useful when needing to perform maintenance on an individual
compressor. The corresponding alarms are still managed.
The following parameters are used: M01,M02,M03,M04 to enable the manual operation of the compressors. The function is managed using parameters:
M05,M06,M07,M08.
4.7. Special MT-LT units
4.7.1. Management of compressor racks with LT and MT circuits and condenser only.
The hardware features of the µrack controller can be adapted for the control of a special type of compressor rack that is becoming more widely used in small and
medium installations, having the advantage of being compact and offering low cost solutions.
These are compressor racks with only the condensing section, and with fan speed managed by the speed controller or external pressure switches, and separate
management of the compressors in the MT and LT units.
Below is an example diagram:
This type of system can be controlled by µrack in the following conditions:
1. the compressors must have the SAME CAPACITY
2. the max number of compressors in the MT unit and LT unit is 4. There can therefore be combinations of 2+2, 3+1, 1+1. One compressor rack will be
allocated to probe LP1, and the other compressor rack to probe LP2.
4.7.2. Probes and values controlled
Value Probe Label Type of unit:
A- Single circuit compressor rack
B- Compressor racks with 2 circuits (MT-LT)
Low pressure BP1 S1 (pressure) LP1 A -B
Low pressure BP2 S2 (pressure) LP2 B
High pressure HP1 S2 (pressure)
S3 (temperature)
HP A (press – temp)
B (only temp)
Temperature 1 S3 (temperature) S3 A (AUX probe)
B (not used)
Temperature 2 S4 (temperature) S4 Always present
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