Dunham-Bush ACDX, Installation, Operation And Maintenance Instructions

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KEY TO WIRING DIAGRAM INDEXING SYSTEM
The wiring diagrams and sequence instructions on the following pages have been devised to simplify the
understanding and tracing of circuit theory. The following key shows how the indexing system can be used.
9 Line number on wiring diagram
[9] Line number in text
(1CR) Component identification symbol in text (Control Relay #1)
(50) Normally open contact -- line number location
(1) Normally closed contact -- line number location
SEQUENCE OF OPERATION (TYPICAL)
MODELS ACDX40-120 A GENERATION
(Ref. Typical Wiring Diagrams on pages 26, 27 & 28)
The following sequence of operation is typical of all to the desired leaving water temperature (e.g. 44
E
F).
electromechanical ACDX Models. Refer to the wiring Set point adjustment is accomplished directly on the
diagram furnished with the unit for specific control. Initial control band setting is 4.0.
information.
( ) Control Identification Symbol S3) in the "On" position, thus energizing the balance
[ ] Circuit Line Number of the control circuit. All safety controls must be
Important Note! for five minutes before the first compressor will start.
With all the control circuit switches (S1-S3) in the "off"
position, Terminals #1 and #2 on the Terminal Board
Stage 1 Starting
(3TB) must have 115 volts supplied for a minimum of Upon demand for cooling, the first step of the staging
24 hours to energize the compressor crankcase thermostat (4TAS) will close energizing relay (8CR).
heaters (1HTR, 2HTR). If all the safety controls and switches are closed, (see
Preliminary Sequence contactors for Compressor No. 1 will energize and the
Close the main power disconnect switch. Check to compressor will start. The liquid line solenoid (1SOL)
see that the indicating light on the under voltage relay will also be energized and refrigerant flow starts.
(UVR) is lit. This light must be on to indicate
proper phase rotation for the compressors. If the
Auxiliary switch (1M1-1) opens to de-energize oil
light is not on, disconnect the main power and reverse sump heater (1HTR) and switch (1M1-2) closes to
any two phase legs at the Main Incoming Power activate the fan control circuit.
Terminal Block. (WARNING! DO NOT REVERSE
THE LEADS ON THE PHASE LOSS MONITOR FOR
The fan motors are controlled by fan cycling controls
THIS WILL ALLOW THE COMPRESSORS TO RUN (10PS-1,2,3 & 4) and will cut in at the factory set
BACKWARDS, CAUSING SEVERE DAMAGE, AND condenser pressures shown on the wiring diagram.
WILL VOID THE COMPRESSOR WARRANTY!)
The crankcase heater relay contacts (1M1-1) and begins timing. If suction pressure does not rise above
(2M1-1) are closed and are supplying power to the setpoint within 120 seconds, the compressor will be
compressor crankcase heaters. Power must also be shut down.
supplied to the chiller heater (CHR HTR) by the
separate customer supplied 115 VAC supply.
Timer (7TR-1) contacts stay in the NC position to
Control power is turned on by the Control Power the compressor in the full unload position for 30
Switch (S1). UVR contacts must close to activate seconds. After (7TR-1) times out (30 seconds), the
1CR and temperature freezestat (2TAS) must also be contacts for the fast unloader solenoid (2SOL) open
satisfied to allow compressor operation. and the NO contacts close, which energizes the relay
Start up the chilled water pump. The water flow is
confirmed when the water flow switch completes the
Stage 1 Modulation
electrical circuit across Terminals #8 and #9 and Upon energizing relay coil (2CR), the NO contacts of
when chilled water pump auxiliary (CWP) closes relay (2CR) are closed, allowing the thermostat
between #9 and #10. (4TAS) to energize the load solenoid (3SOL) and the
Check to make sure time clock contacts close during
occupied modes and then set the thermostat (4TAS)
Place the two compressor control circuit switches (S2-
satisfied and the system may be in a "Time-in" mode
"Safety Controls" section for more detail) the
If suction pressure is low, pressure switch (9PS-1)
power the fast unloader solenoid (2SOL) which holds
(2CR).
unload solenoid (7SOL) upon demand.
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