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Each control circuit board has two modular jacks which
accept RJ–12 telephone plugs. One jack is vacant, the
other has a short pigtail plugged into it. To interconnect
two compressors, plug the cable into the vacant jack on
each controller. For installations of more than two
units, the pigtail plug must be disconnected on all con-
trollers except the two at each end of the communica-
tions line. The order of interconnection has no effect on
the system operation. The following conditions are
necessary and sufficient for proper operation:
1.
Every compressor must have a cable connecting
it to another compressor. One less cable than the
number of units sequenced must be used.
2.
Each board that has only one cable connected to
it must have its pigtail plugged into the unused
jack. All installations will have two such units.
Operation
1.
ESTABLISHING THE INITIAL SEQUENCE
Operation of compressors in sequence requires only a
press of the ‘sequence’ key on each compressor in the
system. Since the sequencing algorithm includes pro-
visions for automatic replacement of a failed master or
‘lead’ compressor, it is important for the operator to be
aware of the hierarchy of events when starting the sys-
tem.
The first compressor placed into sequence mode will
become the master. However, since any compressor
first placed into sequence has no way of knowing
whether or not a master exists, it will first assume the
highest rotation number available. For example if the
number of units to be sequenced is programmed at
four, any compressor will start out in position four when
placed in sequence mode. It will then listen on the com-
munications line for a call from the master.
If no call is received, it will assume position three and
again wait for a call from the master. After another lack
of a master call, it assumes position two. Subsequent-
ly, it assumes position one which makes it the master.
As soon as a master is established, it immediately at-
tempts to call all other units and assigns them succes-
sive rotation positions. The system is now active.
Before a master is established, the system is not de-
prived of air. This is due to one of the outstanding fea-
tures of the “AUTO SENTRY
–ES” sequencing sys-
tem: pressure control is always executed locally at
each individual compressor. The effective setpoint for
compressor control is the programmed setpoint mi-
nus 3(rotation number – 1). So while a compressor
(or compressors) is/are counting down towards estab-
lishing a master, they are also capable of delivering air
at a pressure determined by the above formula.
To ensure that two or more machines do not simulta-
neously decrement their rotation numbers and simulta-
neously become masters, it is advisable to place the
desired master in sequence mode first and wait until
the first decrement in rotation number is seen (about 7
seconds) before placing subsequent compressors in
sequence mode. If it is desired to dictate the complete
initial sequence manually, wait until the previous ma-
chine decrements one position and then place the next
desired compressor in sequence mode. If it is accept-
able to let the master determine the initial sequence,
simply wait until the master has decremented its rota-
tion number once, and then place all remaining com-
pressors in sequence mode. Remember that once a
master is established, no further self–decrementing is
done by the individual compressors. Instead, they will
wait until the master assigns them a rotation number.
Rotation numbers are displayed in the bottom display
line, with the mode indication. For example, the mode
indication for the current master is SEQ1; for the first
lag compressor, SEQ2; second lag, SEQ3; etc.
2.
HOW THE “AUTO SENTRY
–ES” CONTROLS
PRESSURE WHILE SEQUENCING
Each compressor operates exactly the same as if it
were in AUTO mode with one exception: it has a dy-
namic setpoint. The initial setpoint is determined by the
equation shown above. A compressor is started when
the system pressure drops below its programmed reset
point, after waiting for [‘LAG START INTERVAL’
times (rotation number – 1)] seconds. This prevents
all lag compressors from starting at once. Note that a
compressor’s [‘LAG START INTERVAL’ times (rota-
tion number – 1)] timer is not reset to zero until that
compressor is started or until another unit in the system
stops. This means that the time for the next lag com-
pressor to come on may be somewhat less than ‘LAG
START INTERVAL’.
EXAMPLE:
In a three compressor sequence system, SET PRES-
SURE = 100 PSI; RESET PRESSURE = 90 PSI; LAG
START INTERVAL = 15 seconds. The lead compres-
sor is running alone, maintaining 100 PSI by modula-
tion when an air tool is brought on line causing the air
demand to exceed the capacity of the lead compressor.
When the pressure drops to 90 PSI, the #2 unit times
out its 15 second timer and starts. It takes 5 additional
seconds for the pressure to rise above 90 PSI. The #3
unit whose timer was initially set at 30 seconds (15 x [3
– 1]), has counted down 20 seconds (the total time that
system pressure was below 90 PSI). If air demand in-
creases again, the pressure will have to fall below 90
PSI for only 10 seconds more to start unit #3.
As was previously stated, a lag compressor’s modula-
tion setpoint (PSET for short) is [SET PRESSURE –
3(rotation number – 1)]. Thus in the above example,
Summary of Contents for TWISTAIR EWDQ D
Page 14: ...13 11 602 Page 4 FIGURE 1 6 AIR WATER SCHEMATIC FIGURE 1 7 OIL SCHEMATIC...
Page 17: ...13 11 602 Page 7 DECALS 206EAQ077 212EAQ077 218EAQ077 211EAQ077 207EAQ077...
Page 18: ...13 11 602 Page 8 DECALS 216EAQ077 206EWD077 222EAQ077 221EAQ077 208EAQ077...
Page 35: ...13 11 602 Page 25 FIGURE 4 2 FLOW CHART FOR SET UP PROGRAMMING...
Page 44: ...13 11 602 Page 34 FIGURE 4 6 CONTROL TUBING SCHEMATIC 206EWD797 A Ref Drawing...
Page 48: ...13 11 602 Page 38 FIGURE 4 10 WIRING DIAGRAM FULL VOLTAGE 202EWD546 REF DRAWING...
Page 49: ...13 11 602 Page 39 FIGURE 4 11 WIRING DIAGRAM WYE DELTA 203EWD546 REF DRAWING...
Page 50: ...13 11 602 Page 40 FIGURE 4 12 AUTO SENTRY ES CONTROLLER DISPLAY...
Page 53: ...13 11 602 Page 43 FIGURE 5 2 FLOW DIAGRAM AIR COOLED 202EWD797 B Ref Drawing...
Page 54: ...13 11 602 Page 44 FIGURE 5 3 FLOW DIAGRAM WATER COOLED 203EWD797 A Ref Drawing...
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