Installation and Maintenance Manual

Controls
RTAE-SVX001B-EN 45
Starting is Inhibited by External
Source
The chiller is inhibited from starting (and running) by the “external stop” hardwired input.
Start Inhibited by BAS
The chiller is inhibited from starting (and running) by command from a Building Automation System via
the digital communication link (com 4 or com 5).
Waiting for BAS Communications
This is a transient mode - 15-min. max, and is only possible if the chiller is in the Auto - Remote command
mode. After a power up reset, it is necessary to wait for valid communication from a Building Automation
System (Tracer) to know whether to run or stay inhibited. Either valid communication will be received from
the Building Automation System (e.g. Tracer), or a communication diagnostic ultimately will result. In the
latter case the chiller will revert to Local control.
Power Up Delay Inhibit min:sec
The compressor is currently being inhibited from starting as part of the power up start delay (or staggered
start) feature. This feature is intended to prevent multiple chillers from all starting simultaneously if power
is restored to all chillers simultaneously.
Low Differential Refrigerant Pressure
Cool-Down Timemin:sec
Contact your local Trane service office.
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 the Differential to Start.
Waiting to Start
The chiller is not currently running and there is a call for cooling but start is delayed by certain
interlocks or proofs. Further information is provided by the sub-mode:
Waiting For Cond Water Flow
The chiller will wait up to 20 minutes in this mode for condenser water flow to be established per the flow
switch hardwired input.
Start Inhibited Waiting for Oil The chiller will wait up to 2 minutes in this mode for oil level to appear in the oil tank.
Condenser Water Pump Pre-Run
Timemin:sec
The chiller will wait up to 30 minutes (user adjustable) in this mode for to allow the condenser water loop
to equalize in temperature
Restart Inhibit min:sec
The compressor is currently unable to start due to its restart inhibit timer. A given compressor is not
allowed to start until 5 minutes (adj) has expired since its last start, once a number of “free starts” have
been used up.
Waiting For EXV Preposition
The Chiller will wait for the time it takes the EXV to get to its commanded pre-position prior to starting
the compressor. This is typically a relatively short delay and no countdown timer is necessary (less than
15 seconds)
Minimum Condenser Watermin:sec
Only possible when Condenser Head Pressure Control option is enabled, this wait may be necessary due
to the Head Pressure control device’s stroke time.
Condenser Water Regulating Control
min:sec
Only possible when Condenser Head Pressure Control option is enabled, this wait may be necessary due
to the Head Pressure control device’s stroke time
Running
The chiller, circuit, and compressor are currently running. Further information is provided by
the sub-mode:
High Discharge Temp Limit
The compressor is running and is being forced loaded to its step load point, without regard to the leaving
water temperature control, to prevent tripping on high compressor discharge temperature.
Base Loaded
Chiller is running in “Base Load” operation where the capacity of the chiller is controlled to maintain a given
current per an adjustable set point. The chiller is forced to run without regard to the chilled water
temperatures and the differential to start and stop
Capacity Control Softloading
The chiller is running, but loading is influenced by a gradual ‘pulldown” filter on the chilled water
temperature setpoint. The settling time of this filter is user adjustable as part of the softload control
feature.
Current Control Softloading
The chiller is running, but loading is influenced by a gradual filter on the current limit setpoint The starting
current and the settling time of this filter is user adjustable as part of the softload control feature.
EXV Controlling Differential Pressure
Liquid level control of the Electronic Expansion Valve has temporarily been suspended. The EXV is being
modulated to control for a minimum differential pressure. This control implies low liquid levels and higher
approach temperatures, but is necessary to provide minimum oil flow for the compressor until the
condenser water loop can warm up to approx 50F.
Chilled Water Control
Unit is running in the Cooling Mode of operation and is attempting to control to the active Chilled Water
Setpoint.
Running – Limited
The chiller, circuit, and compressor are currently running, but the operation of the chiller/
compressor is being actively limited by the controls. Further information is provided by the sub-
mode.* See the section below regarding criteria for annunciation of limit modes
Table 24. Operating modes (continued)
Chiller Modes Description