Controls
38
RTAF-SVX001A-EN
Starting is Inhibited by External
Source
The chiller is inhibited from starting or running by the “external stop” hardwired input.
Power Up Delay Inhibit: min:sec
On power up, the chiller will wait for the Power Up Delay Timer to expire.
Run Inhibit
The chiller is currently being inhibited from starting (and running), but may be allowed to start
if the inhibiting or diagnostic condition is cleared. Further information is provided by the sub-
mode:
No Circuits Available
The entire chiller is stopped by circuit diagnostics or lockouts that may automatically clear.
Ice Building Is Complete
The chiller is inhibited from running as the Ice Building process has been normally terminated on the
evaporator entering temperature. The chiller will not start unless the ice building command (hardwired
input or Building Automation System command) is removed or cycled.
Ice to Normal Transition Inhibit
The chiller is inhibited from running for a brief period of time if it is commanded from active ice building
mode into normal cooling mode via the ice building hardwired input or Tracer. This allows time for the
external system load to “switchover” from an ice bank to the chilled water loop, and provides for a
controlled pull down of the loop’s warmer temperature. This mode is not seen if the ice making is
automatically terminated on return brine temperature per the mode below.
Start Inhibited by BAS
The chiller is stopped by Tracer
®
or Building Automation System.
Starting is Inhibited by External
Source
The chiller is inhibited from starting or running) by the “external stop” hardwired input.
Diagnostic Shutdown – Auto Reset
The entire chiller is stopped by a diagnostic that may automatically clear.
Starting is Inhibited by Low Ambient
Temperature
The chiller is inhibited based on the outdoor air temperature.
Power Up Delay
Inhibit: min:sec
On power up, the chiller will wait for the Power Up Delay Timer to expire.
Chilled Water Control
Chiller is running to provide a chilled water temperature per the active chilled water setpoint (may be as
arbitrated from various sources). (For cooling only units, this mode may be suppressed.)
Auto
The chiller is not currently running but can be expected to start at any moment given that the
proper conditions and interlocks are satisfied. Further information is provided by the sub-
mode:
Waiting For Evap Water Flow
The chiller will wait up to 20 minutes in this mode for evaporator water flow to be established per the flow
switch hardwired input.
Waiting for A Need to Cool
The chiller will wait indefinitely in this mode, for an evaporator leaving water temperature higher than the
Chilled Water Setpoint plus some control dead-band.
Chilled Water Control
Chiller is running to provide a chilled water temperature per the active chilled water setpoint (may be as
arbitrated from various sources). (For cooling only units, this mode may be suppressed.)
Waiting to Start
The chiller is not currently running and there is a call for cooling but lead circuit start is delayed
by certain interlocks or proofs.
No chiller sub-modes.
Running
The chiller, circuit, and compressor are currently running. Further information is provided by
the sub-mode:
Chilled Water Control
Chiller is running to provide a chilled water temperature per the active chilled water setpoint (may be as
arbitrated from various sources). (For cooling only units, this mode may be suppressed.)
Maximum Capacity
The chiller is operating at its maximum capacity.
Capacity Control Softloading
The control is limiting the chiller loading due to capacity based softloading settings.
Demand Limit Softloading
The chiller is running, and loading of individual compressors may be limited by a gradual filter of the chiller’s
softloading demand limit setpoint. The starting demand limit and the settling time of this filter is user
adjustable as part of the demand limit softload feature. The mode will be displayed as long as the Demand
Limit Softloading is ramping or “settling”.
Running – Limited
At least one circuit on the chiller is currently running, but the operation of any of the circuits on the chiller
is being actively limited by a chiller level limit. Other sub modes that apply to the Chiller Running top level
modes may also be displayed here. Refer to the list of circuit limit modes for circuit limits that will cause
display of this Chiller Level Running Limit mode.
Demand Limit
The chiller is running and the compressor capacity is unloaded or restricted to load slowly or not at all to
keep the chiller from exceeding the demand limit set by the customer.
Demand Limit Softloading
The chiller is running, and loading of individual compressors may be limited by a gradual filter of the chiller’s
softloading demand limit setpoint. The starting demand limit and the settling time of this filter is user
adjustable as part of the demand limit softload feature. The mode will be displayed as long as the Demand
Limit Softloading is ramping or “settling”.
Table 18.
Operating modes (continued)
Chiller Modes
Description
