33
Ductless
Fume
Hoods
Problem
3:
Airflow
Failure
(AIRFAIL)
–
alarm
is
triggered
Cause
Corrective
Action
External
air
interference
•
Ensure
that
there
are
no
external
sources
of
airflow
disturbance
like
air
conditioner
vent,
window
or
incidences
of
door
opening
or
people
walking
fast
near
the
cabinet.
•
Locate
airflow
sensor
installed
inside
the
work
zone.
Ensure
there
is
no
air
disturbance
or
obstruction
around
the
sensor.
•
If
there
is
no
external
air
interference,
proceed
to
next
step.
Blocked
cabinet
grille
•
Ensure
that
the
air
grilles
inside
the
cabinet
are
not
blocked
and
that
the
cabinet
is
not
excessively
loaded.
•
If
there
is
no
blockage
in
air
grilles,
proceed
to
next
step.
Low
building
supply
voltage
(if
new
cabinet,
check
this
first)
•
Turn
on
the
cabinet.
•
Open
electrical
box
and
find
motor
voltage
sampling
port
as
shown
on
Figure
3
‐
1.
•
For
new
cabinet,
if
the
motor
voltage
is
lower
than
the
Nominal
Voltage
value
recorded
in
factory
test
report,
adjust
the
speed
controller
to
get
output
voltage
to
blower
as
specified
in
the
Test
Report
–
Test
Conditions
Documentation
Sheet.
•
For
cabinet
that
has
been
used
for
more
than
1
year,
refer
to
last
motor
Nominal
Voltage
from
last
certification
report
or
if
not
available,
measure
the
actual
airflow
on
cabinet
and
increase
motor
voltage
accordingly
to
achieve
nominal
airflow
velocity.
•
If
supply
voltage
is
same
as
Nominal
Voltage,
proceed
to
next
step.
Filter
loaded
or
wrong
speed
controller
setting
•
Plug
in
the
voltmeter
to
the
Motor
Voltage
Sampling
Port.
•
Measure
the
actual
airflow
velocity
using
anemometer
or
flow
hood.
If
actual
airflow
is
okay
but
LCD
still
shows
AIRFAIL,
proceed
to
next
step.
If
actual
airflow
is
not
okay,
please
adjust
motor
speed
controller
accordingly
until
alarm
is
turned
off
and
the
LCD
shows
nominal
airflow
reading.
After
this,
if
LCD
still
shows
AIRFAIL,
proceed
to
next
step.
•
The
sensor
will
take
about
2
‐
3
minutes
before
it
can
register
a
new
airflow
setting.
Note:
The
cabinet
must
be
certified
at
least
annually.
•
If
the
blower
is
already
operating
at
maximum
voltage
and
the
airflow
alarm
is
still
triggered
due
to
filter
loaded,
it’s
time
to
change
the
filter.
•
If
filter
is
not
loaded,
proceed
to
next
step.
Faulty/
inaccurate
calibration
•
Re
‐
calibrate
the
microprocessor.
Follow
the
calibration
procedure
in
the
test
report.
Warning:
To
be
carried
out
only
by
an
authorized
person.
CHECKING
CALIBRATION
DATA
•
After
calibration
is
done,
go
to
MENU,
key
in
PIN
if
required,
choose
SET
MODE,
and
choose
MAINTENANCE.
•
LCD
will
blink
in
MAINTENANCE
MODE.
•
Go
to
main
display
by
pressing
MENU
button
twice.
•
Press
SET
button,
LCD
will
display
software
version
that
is
currently
being
used
on
the
cabinet.
Example:
C201
V3.0
Figure
3
‐
1
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