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Sequential mode
% Load to start next = 100 , % Load chiller to stop next = 85
Switch-on
The first chiller is always On. The second chiller is switched-on when the first is at 100%. The third chiller is switched-on when the other two are at
100%
Switch-off
The third chiller is switched-off when it is expected that the two remaining switched-on do not increase the power beyond 85%.
(by switching a chiller on the plant return temperature is decreased and therefore the power of the chillers that are switched-on. By switching a
chiller off, the plant return temperature increases and therefore the power of the chillers that are switched-on).
The second chiller is switched-off when it is expected that the only chiller remaining on does not increase the power beyond 85%.
Homogeneous mode
% Load to start next = 0 , % Load chiller to stop next = 0 ()
RECOMMENDED FOR PLANTS WITH UNIQUE PUMP ON PRIMARY CIRCUIT
OR PLANT WITH FIXED CAPACITY SECONDARY CIRCUIT
The chillers must be switched-on and off all at the same time (the delays between set chiller switch-on/switch-off are howe-
ver respected), they therefore work in parallel.
Combined mode
% Load to start next = 80 , % Load chiller to stop next = 60
Switch-on
The first chiller is always On. The second chiller is switched-on when the first is at 80%. The third chiller is switched-on when the
other two are at 80%
Switch-off
The third chiller is switched-off when it is expected that the two remaining switched-on do not increase the power beyond 60%.
(by switching a chiller on the plant return temperature is decreased and therefore the power of the chillers that are switched-on.
By switching a chiller off, the plant return temperature increases and therefore the power of the chillers that are switched-on)
The second chiller is switched-off when it is expected that the only chiller that is switched-on does not increase the power beyond
60%.
RESET SET POINT
In the case of LOAD type adjustment, when the chiller is in the condition to be switched-off, it is possible to anticipate the increase of power of the chillers
that are still switched-on (switching a chiller off increases the plant return temperature and therefore the power of the chillers that are still switched on),
by changing the chiller work set point for a time anterior and posterior to switch-off of the chiller (set point reset). This function helps to prevent signifi-
cant rises in temperature in these transients.
The set point to which the delta set point reset is added/subtracted is that currently used by the cards depending on the functioning mode, multifunction
inputs, double set points.
Cold set point = Set point - Delta set in Set point reset
Cold set point = Set point + Delta set in Set point reset
Delay for setpoint reset before
Delay for setpoint reset after
Conditions for switching off active chiller •
• Chiller switch off
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