Owner`s manual

OM-263 001 Page 27
6-4. Operating The Controller
Description
The controller continuously monitors and
displays differential pressure drop in inches
of water or decaPascals on the panel face.
When combined with a pulse timer, it can
control the extractor cleaning mechanism to
maintain the differential pressure drop
between chosen limits. Three cleaning
modes are available along with an alarm
function and a 4 – 20 mA signal output.
 Abnormal changes in pressure drop in
dicate a change in operating conditions
and possibly a fault to be corrected. For
example, prolonged lack of com
pressed air will cause an excess
build‐up of particles on the filters result
ing in increased pressure drop. Down
time cleaning with no flow usually re
stores the filters to normal pressure
drop.
Normal Operation
Three cleaning modes, Differential Pres-
sure Cleaning (DFF), Downtime Cleaning
(DTC), and Combined Differential and
Downtime Cleaning (ALL) are available with
this controller and can be individually
chosen by the user.
 Differential Pressure Cleaning (DFF)
− When the differential pressure drop
reaches the controller’s High set-
point, the controller closes an output
relay initiating the cleaning cycle.
When the differential pressure drop
reaches the Low setpoint, the relay
opens and the cleaning cycle stops.
This sequence continues as long as
the extractor is running, maintaining
the differential pressure drop within a
specified range.
 Downtime Cleaning (DTC) – The con-
troller monitors for the differential
pressure drop to exceed the Low set-
point (indicates the blower has been
started). When the differential pres-
sure drop later approaches zero (in-
dicating the blower has been shut
down), the controller engages the
cleaning cycle for a pre−selected
time. A delay timer allows the blower
to come to a stop before the cleaning
cycle starts.
 The downtime cleaning cycle begins 90
seconds (factory setting) after the sys-
tem is shut down. Downtime cleaning
activates only if the differential pressure
drop across the filters is above the low
setpoint (factory setting of 2 in. w.g.)
when the system is stopped.
 The delay timer and cleaning cycle dur-
ations are both user adjustable but
password protected.
 Combined Differential and Downtime
Cleaning (ALL) –The ALL mode com-
bines the two functions described
above, maintaining the differential
pressure drop in a specified range,
then initiating a down−time cleaning
cycle when the differential pressure
drop approaches zero. The downtime
cleaning function can be toggled on or
off from the keyboard.
 The DTC and ALL cleaning modes in-
corporate compressed air cleaning of
the filters when the main extractor fan is
not running. This may result in collected
material “drifting” out the inlet duct of the
extractor. An isolation valve in the inlet
duct of the extractor can reduce or elim-
inate that drifting.
Consideration should be made on the
use of the DTC or ALL cleaning mode
on small extractors where the relatively
low volume of the extractor may pro-
duce pressure spikes with each pulse of
the cleaning cycle. Such pressure
spikes may accelerate the fatigue, or
damage of ancillary items such as pres-
sure sensors or explosion relief panels.
Alarm
The alarm is used to indicate that the differ-
ential pressure drop has exceeded a preset
value. The alarm setpoint is set to a value
exceeding the High setpoint used to start the
filter cleaning cycle. The purpose of the
alarm is to notify the user, via a light on the
panel or dry-contact output, that the clean-
ing system cannot reduce the pressure drop
due to a cleaning system failure, lack of
compressed air, or the end of the filter’s use-
ful life. It can also be used to notify the user
that the pressure drop has reached a certain
value (process related). There is a time
delay prior to activating the alarm to prevent
nuisance trips of the alarm. The controller
also provides an input connection for a re-
mote alarm reset/disable.
 Once the differential pressure drop
reaches the Alarm value, the relay and
LED remain activated until the pressure
drop falls below the value set for the
HIGH set point or until you deactivate
the alarm using a remote reset/disable.
“wg
daPa
Alarm Cleaning
Downtime
Clean
Menu
Set