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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 controllers except the two at each end of the commu-
nications line. The order of interconnection has no ef-
fect on the system operation. The following conditions
are necessary and sufficient for proper operation:
1.
Every compressor must have a cable con-
necting it to another compressor. One less
cable than the number of units sequenced,
must be used.
2.
Each board that has only one cable con-
nected to it must have its pigtail plugged into
the unused jack. All installations will have two
such units.
3.
Each unit must be programmed with the
same set and reset points.
II.
OPERATION
A.
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 relacement 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 in sequence mode will be-
come the master. However, since any compressor first
placed in sequence has no way of knowing whether or
not a master exists, it will first assume the highest rota-
tion number available. For example if the number of
units to be sequenced is programmed at four, any com-
pressor will start out in position four when placed in se-
quence mode. It will then listen on the communications
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 master call, it assumes position two. Subsequently,
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 system:
pressure control is always executed locally at each indi-
vidual compressor. The effective setpoint for compres-
sor control is the programmed setpoint minus 3(rota-
tion number – 1). So while a compressor (or
compressors) is/are counting down towards establish-
ing a master, they are also capable of delivering air at
a pressure determined by the above formula.
To insure 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 SEQI; for the first lag
compressor, SEQ2; second lag SEQ3,etc.
B.
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 com-
pressor’s [’LAG START INTERVAL’ times (rotation
number 1)] timer is not reset to zero until that compres-
sor is started. This means that the time for the next lag
compressor to come on is always 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-
Summary of Contents for ELECTRA-SAVER EAU PD - 200 HP
Page 13: ...13 10 612 Page 3 FIGURE 1 4 STARTER BOX FIGURE 1 5 PACKAGE CONTROLLER AND STARTERS...
Page 16: ...13 10 612 Page 6 DECALS 206EAQ077 212EAQ077 218EAQ077 211EAQ077 207EAQ077...
Page 17: ...13 10 612 Page 7 DECALS 216EAQ077 217EAQ077 222EAQ077 221EAQ077 208EAQ077...
Page 40: ...13 10 612 Page 30 FIGURE 4 8 CONTROL SCHEMATIC COMPRESSOR AT FULL LOAD 214ECM797 Ref Drawing...
Page 42: ...13 10 612 Page 32 FIGURE 4 10 WIRING DIAGRAM 212EAP546 Ref Drawing...
Page 43: ...13 10 612 Page 33 FIGURE 4 11 AUTO SENTRY ES CONTROLLER DISPLAY...
Page 45: ...13 10 612 Page 35 FIGURE 5 1 FLOW DIAGRAM AIR OIL SYSTEM 215EAU797 Ref Drawing...
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