OMM 1008-1
25
Warnings
Warnings advise that a non-catastrophic problem exists, such as failed temperature sensor that provides a
signal for information, not control purposes. There are no Warnings associated with the compressor
controllers.
Compressor Control Functions
Each compressor determines if it has reached its maximum capacity (or maximum allowed capacity) and if
so, set its Full Load flag. The flag is based on a number of conditions.
Absolute Capacity
Each compressor estimates its absolute capacity from the present value of % RLA and the Absolute Capacity
setpoint from the equation:
Absolute Capacity = (%RLA Factor) * (Absolute Capacity setpoint)
where the %RLA Factor is interpolated from the following table.
%RLA
0
50
75
100
150
%RLA Factor
0
0.35
0.75
1.00
1.50
Multiple Compressor Staging
This section defines which compressor is the next one to start or stop. The next section defines when the
start, or stop, is to occur.
Functions
1.
Can start/stop compressors according to an operator defined sequence.
2.
Can start compressors based on the number of starts (run hours if starts are equal) and stop on run hours.
3.
The above two modes can be combined so that there are two or more groups where all compressors in the
first group are started (based on number of starts/hours) before any in the second group, etc. Conversely,
all compressors in a group are stopped (based on run hours) before any in the preceding group, etc.
4.
An “efficiency priority” mode can be selected for two or more chillers where one compressor is started
on each chiller in the group before a second is started on any of them.
5.
A “pump priority” mode can be selected for one or more chillers where all compressors on a given chiller
are started before going to the next chiller in the group.
6.
One or more compressor can be defined as “standby” where it is never used unless one of the normal
compressors is unavailable.
Required Parameters
1.
Sequence number setpoint (SQ#_SP) for all compressors. Possible settings = (1-4).
2.
Compressor Staging Mode setpoint (CSM_SP) for all compressors. Possible settings are:
•
•
NORMAL
•
•
EFFICIENCY PRIORITY
•
•
PUMP PRIORITY
•
•
STANDBY
3.
Maximum Number of compressors ON setpoint (MAX_ON_SP). Possible settings = (1-4). This setpoint
is the same for all compressors.
4.
Number of starts for all compressors.
5.
Number of run hours for all compressors.
6.
Status of all compressors (On-line, Available/Unavailable, Starting, Running, etc.)
