MAC AVR Installation, Operation & Maintenance Manual - page 9
Publication: MAN3002G
MAC Equipment, Inc.
6
Timer Control Wiring and Adjustment
Refer to Figure 4-5 and to the timer manufacturer
’s documentation.
Figure 4-5 Timer Control and Wiring
1.
Open the timer enclosure and connect the electrical service to the
terminals labeled L1 and L2. If a photohelic switch/gauge (or other
pressure switch) is not used, connect a jumper wire across the
terminals labeled
“Pressure Switch.”
Do not connect power to the
Pressure Switch terminals; the timer board will be damaged.
2.
Check both the "Time-on" and the "Time-off" settings. "Time-on"
determines the duration of the cleaning air blast and should be set at
60 milliseconds. The 60 milliseconds "Time-on" has been
determined as the optimum duration for the majority of applications
and should not be changed unless directed by MAC Equipment, Inc.
Set the "Time-off" to 15 seconds; this is the length of time between
successive cleaning pulses. For example, if the filter has six rows of
bags, each row would be cleaned every 90 seconds, 6 x 15
seconds. After operating experience has been gained, the "Time-
off" setting may be adjusted to the maximum time possible that will
maintain effective bag cleaning, which will conserve compressed air.
When a photohelic differential pressure switch/gauge is used, only
the pressure settings should be adjusted instead of the "Time-off"
setting. Effective bag cleaning is directly related to the differential
pressure. Refer to the Operation Chapter for more information
about differential pressure and adjustment of the switch/gauge.
3.
Check the program wire on the timer board to be sure it is
connected to the pin that corresponds with the number of solenoid
valves mounted on or in the timer enclosure.
4.
Energize the electrical service to the timer. The "Power On" light
should be illuminated and the unit should start pulsing. If a
photohelic switch/gauge is in use, the high pressure setting on the
switch/gauge must be set to zero to start pulsing. After pulsing is
confirmed, restore the setting to its previous value.
5.
De-energize the system as soon as pulsing has been verified;
pulsing the solenoids without the compressed air supply for any
extended period of time can damage the solenoid valves.
Other Electrical Connections
Make electrical connections to the motor(s) on any auxiliary equipment
such as an airlock, screw conveyor or fan. Verify that all motors are
rotating in the proper direction.
NOTE: The motors should be interlocked such that they start in the
following sequence: (1) airlock, (2) AVR timer, and (3) main exhaust fan.
The motors should be shut down in the reverse order. Shut down the
exhaust fan first; using an adjustable time delay (0-15 minutes) shut
down the timer 15 minutes after the exhaust fan. Finally, shut down the
airlock.
If the filter is being used to vent a gas fired dryer, to prevent fires and
explosions, the main exhaust fan must be interlocked with the gas burner
in such a way as to allow the fan to operate an adequate period of time to
purge the dust collector of combustible gases before turning on the
burner. The installation of a gas detection device in the system should be
investigated and evaluated for each application.
Magnehelic Gauge or Photohelic Switch/Gauge
A magnehelic differential pressure gauge is available as an option. The
gauge indicates the difference in pressure between the input and
discharge sides of the filter. An excessively high reading indicates that
filter media are becoming clogged and that more frequent cleaning pulses
are required.
A photohelic switch/gauge is a second option. The photohelic
switch/gauge indicates differential pressure and controls the cleaning
operation. When an electronic circuit in the switch/gauge detects
differential pressure in excess of a predetermined set point, it provides a
dry contact closure which initiates the cleaning cycle. When differential
pressure drops to a predetermined set point, the switch/gauge opens the
contact, thus stopping the cleaning cycle. This method of control reduces
compressed air needed and increases bag life.
To install either type of gauge refer to Figure 4-6 and to the
manufacturers documentation.
HIGH PRESSURE
PORT
(
OPPOSITE SIDE
OF MACHINE
)
LOW PRESSURE
PORT
(
OPPOSITE SIDE
OF MACHINE
)
GAUGE
Figure 4-6 Installation of Differential Pressure Gauge
Installing the Magnehelic Differential Pressure Gauge
1.
Mount the gauge in a convenient place for easy viewing.
2.
Install the tubing fittings in the pressure ports of the magnehelic
pressure gauge and in the ports on the filter. The filter ports are
normally located on the right side of the filter from the service door.
3.
Run the plastic tubing supplied from the filter ports to the gauge
ports. The low pressure line runs from the filter port above the tube
sheet to the low pressure port (usually the lower port) on the gauge.
The high pressure line runs from the filter port below the tube sheet
to the high pressure port (usually the upper port) on the gauge.
4.
Verify that the filter is installed inside the housing on the high
pressure port.
Installing the Photohelic Differential Pressure Switch/Gauge
Install the photohelic switch/gauge and run air piping as for the
magnehelic gauge as described above.
In addition:
1.
Connect electric power to contacts labeled
‘L1’ and ‘L2’ on the
switch/gauge. Refer to the label on the switch/gauge for power
requirements.
2.
Connect contacts labeled
“NO” and “C” on the switch/gauge
to
contacts labeled
“Pressure Switch” on the timer board. (Remove
jumper between the Pressure Switch contacts, if any.)
3.
Install jumpers on the switch/gauge according to the Figure 4-7
below.