Chiller % Rla From A Hardwired Chiller - McQuay MicroTech II Operation Manual

(not used if chiller supplies % RLA)
Current Transducer High Signal Amps
(not used if chiller supplies % RLA)
% RLA Offset
Alarm Switch State
Fault Alarm Proving Time
Number Of Chiller Alarm Outputs
Receive Heartbeat
Leaving Evaporator Water Temp Offset
Leaving Condenser Water Temperature
Offset

Chiller % RLA from a Hardwired Chiller

The CSM displays the chiller's % RLA and uses it on a hardwired chiller when deciding when to perform a stage-up or a
stage-down. Stage-up is possible when this chiller has been operating at a % RLA higher than the Full Load % RLA for a
period of time greater than the Chiller Stage Delay Time.
Stage-down is possible when the spare capacity of all the running chillers (excluding the next-off chiller) is greater than the
capacity that will be lost when the next-off chiller is disabled before a stage-down will occur.
The CSM also uses % RLA on a hardwired chiller to determine when that chiller is in the "running" state. When the %
RLA is higher than the Running % RLA, the chiller is considered to be running. This is an important distinction because if
a chiller is enabled but not running, it will be considered an offline chiller.
If the chiller to be hardwired provides an analog output, which represents % RLA, the output is wired directly to the
hardwired chillers remote I/O module. If this is the case, set the % RLA Input Type property to "% RLA from chiller (4-20
mA)" or "% RLA from chiller (0-10 Vdc)" and set the RLA Signal At 100% based on your particular chiller.
If the chiller to be hardwired does not provide an analog output which represents % RLA, a current transducer (CT) must
be added to the chiller to provide a measurement of running amps. If this is the case, set the % RLA Input Type property to
"Amps from 4-20 mA output CT". Set the Nameplate RLA and Current Transducer High Signal Amps based on your
particular chiller and selected current transformer.
See IM 781 for details on wiring and hardware requirements for % RLA on hardwired chillers.
OM 780-2
associated chiller's Nameplate Rated Load Amps. This value is used to calculate % RLA by measuring
the amps used by the chiller. Default = 150 Amps.
If % RLA is sent from the chiller unit controller this property is not used. This input tells the CSM the
amps associated with the high range of the current transducer's (CT) output signal (20 mA). For
example, if a current transducer with a range of 0-200 Amps is mounted on the chiller and wired directly
to the remote I/O module's AI, the value of this property must be set to 200 (also, set % RLA Input Type
= Amps from 4-20 mA output CT. This value is used to calculate % RLA by measuring the amps used
by the chiller. Default = 200 Amps.
If % RLA is sent from the chiller unit controller this property is not used. Value added to the internally
calculated value of % RLA. Allows for wiring or sensor-to-system compensation. Range = Can be
positive or negative as needed. Default = 0.
This property defines which chiller alarm contact position is used to indicate alarm. If a contact opening
from the chiller indicates an Alarm, set this property to "Open". If a contact closure from the chiller
indicates an alarm, set this property to "Close". Default = "Open".
This property defines how long a chiller's alarm contact must be in the alarm state (open or closed based
on the Alarm Switch State property) before the CSM recognizes a chiller fault. This is required for the
CSM to differentiate between a fault alarm (steadily switched contacts) and a problem alarm (flashing
contacts). Range = 2 to 60 seconds. Default = 16 seconds.
This property tells the CSM if the chiller will be providing one or two alarm signals. If a multiple
compressor chiller has two separate alarm indicators, wire the second contacts to DI 4 on the remote I/O
module. The CSM will then calculate the chiller's availability based on alarm information from both
signals. If a chiller has two alarm outputs, when one output indicates fault alarm, the chiller will be
considered to have 50% of its capacity unavailable, if both outputs indicate fault alarm, the chiller will be
considered unavailable. Range 1 or 2 outputs. Default = 1 output.
For example; a MicroTech Series 200 Centrifugal chiller has two alarm outputs.
Note: If the property is set = 2, this chiller's Number Of Compressors property must be set = 2.
This input defines the length of time (in seconds) the hardwired chiller's remote I/O module waits
without receiving a command from the CSM before determining that communications have been lost. If
this value = 0 and communication loss occurs, an enabled chiller will remain enabled at it current
setpoints until communications are restored. If this value is set to be greater than 200, an enabled chiller
will be disabled if communication loss occurs. Range = 0 seconds and any number of seconds greater
than 200. Default = 0 seconds (Comm loss features disabled, chiller will remain in existing state if
communications is lost).
This value is added to the measured temperature values for calibration purposes allowing for wiring or
sensor-to-system compensation. Range = Can be positive or negative as needed. Default = 0.
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