Airedale LogiCool FreeCool 40kW - Manual (Page 12)

LOGICOOL
™
Chillers
12
Chillers
Technical Manual : 6521355 V1.8.0 07/2014
Design Features & Information
DIGITAL SCROLL COMPRESSORS
General Description Digital scroll compressor technology offers compressor capacity modulation from 20% to
100% achieved by the use of an externally integrated long life electronically controlled
solenoid valve which loads and unloads the compressor scroll based on a 20
second cycle.
The solenoid valve uses suction and discharge pressures through a modulation chamber
to cause a spring loaded piston attached to the top scroll to fall down at high pressure and
move up at low. The moving of the piston separates the scrolls and results in no
compression of refrigerant.
As the digital compressor is always operating at either 100% or 0% the mass flow of
refrigerant through the system is always high, simplifying component selection and pipe
work design to guarantee oil return.
Energy Efficiency The digitally modulated solenoid achieves capacity modulation of 20% to 100% by varying
the loaded or unloaded compressor cycle time and averaging the sum of the loaded and
unloaded state. The digital scroll compressor operates in an unloaded state for a
proportion of the 20 second cycle time; as a result, the load on the compressor is greatly
reduced as refrigerant is not drawn. Consequently the energy consumed at partial load
condition is only a percentage of that consumed during full load condition, ie:
(Loaded Time x 100%) + (Unloaded Time x 10%)
= Average Power
(Loaded Time + Unloaded Time)
Operation The following examples illustrate the flexibility of the digital compressor loading stages
within the 20 second cycle time:
Example A Where: Solenoid Energised = 10 seconds Loaded Time
Solenoid De-energised = 10 seconds Unloaded Time
(10 x 100%) + (10 x 0%)
= 50%
20
10 Secs 10 Secs 100% Capacity
0% Capacity
10 Secs 10 Secs
20 Secs
Example B
Where: Solenoid Energised = 5 seconds Loaded Time
Solenoid De-energised = 15 seconds Unloaded Time
(15 x 100%) + (5 x 0%)
= 75%
20
5 Secs 5 Secs
15 Secs 15 Secs
20 Secs