Lennox CLIMATIC 60, User Manual

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CLIMATIC™ 60 – AIRCOOLED CHILLERS
MUL 41E -0610/ 06-2011 Page 15
8.4 6 Control
The Climactic™60 adjusts and hold the fluid outlet temperature as close as possible to the set point, by controlling
the number of compressor stages depending on the thermal load of the system. The controller calculates
constantly the required capacity to reach the temperature set point. This variable is called “CAPACITY FACTOR”
(CF) and its value can vary from 0 to 100%. It is directly linked to the number of control stages of the unit. Thus for
a unit with 4 stages of regulation, the CF will start and stop a stage with the following values: ~0-25-50-75-100%. It
then evolves following the principles detailed in the diagram.
In order to anticipate, the reference point is recalculated each time the difference between air temperature and set
point reach a minimum or a maximum.
Moreover the inlet temperature is used to limit the capacity factor to prevent from too slow reactivity of outlet
capacity factor of the unit.
Example :
• Unit EAC 2104: cooling capacity: 210KW with:
• C1.Cp1 = 19.2%,
• C1.Cp2 = 30.8%,
• C2.Cp1 = 19.2%,
• C2.Cp2 = 30.8%.
• Maximum delta T° (inlet - outlet) at full load: setting ( 3261 ) = 5.0°C.
• Outlet water evaporator temperature set point: setting ( 3238 ) = ( 3239 ) = 7.0°C.
Stage
Minimum
Inlet temp.
(°C)
Maximum
capacity factor
(%)
Expression
Compressor
ON circuit 1
Compressor
ON circuit 2
0 0 0 0
1 8.54 30.8 7.0 + 30.8*5.0/100
2 10.80 61.6 7.0 + 2*30.8*5.0/100
3 11.04 80.8 7.0 + (19.2+2*30.8)*5.0/100
4 12.00 100.0 7.0 + 2*(19.2+30.8)*5.0/100
Difference between
the outlet water
temperature and the
set point
Water Temperature
Change rate
0
+ 2K
-
-
FAST SLOW
CF FROZEN
CF INCREASES
(Start more Capacity Stages)
CF FROZEN
CF DECREASES
(Removes Capacity Stages)
+ 1K
SLOW FAST