60/6
DEFROST
CONTROL
Air
Defrost
Sequences:
-
Stop
compressor,
while
keeping
the
fans
running
by
means
of
the
timer
or
the
controller.
preferably
following
a
pump
down
to
drain
the
air
cooler,
but
without
creating
a
vacuum
(the
vapour
acting
as
a
conductor
in
a
vacuum).
-
Keep
fans
running
during
the
full
defrost
-
Return
to
cooling
by
means
of
timer
or
control
switch.
Electrical
defrost
Sequences:
-
Stop
compressor
and
the
fans
by
means
of
the
timer
or
the
control
switch
but
preferably
after
a
pump
down
to
drain
the
air
cooler,
but
without
creating
a
vacuum
(the
vapour
is
conductor
in
a
vacuum).
Allow
the
heaters
to
warm
up.
1)
The
heaters
are
controlled
by
a
Defrost
Termination
Thermostat
(when
ambient
air
temperature
has
been
reached).
Cooling
is
restarted
by
the
position
of
the
thermostat
bulb
which
detects
the
pre-set
temperature
which
must
not
exceed
10°C.
The
most
suitable
point
on
the
coil
is
to
be
used
at
frost
level.
The
clock
or
controller
acts
as
a
safety
device
for
restarting
cooling,
if
this
is
not
done
by
the
thermostat.
2)
Theheatersarecontrolledbya
Limiter
Thermostat(whenambientairtemperaturehasbeenreached).
Cooling
is
restarted
by
timer
or
controller
reaching
its
time
limit.
The
bulb
is
positioned
a
the
top
of
the
coil,
on
the
injection
side
in
a
free
space.
Insert
the
bulb
as
far
as
possible.
In
this
case,
the
pre-set
temperature
will
be
from
7°C
to
9°C
with
a
minimum
differential
(2K)
As
the
thermostat
operates
the
heaters
during
defrost,
the
coil
temperature
evens
out,
which
allows
vapour
production
to
be
reduced.
Restart
cooling:
1)
Forcoldroomsatpositivetemperatures(forproducewhichmuststaydry)
-
Restart
cooling
(End
of
Defrost
or
Limiter)
with
icing
(1
min)
to
avoid
water
splashes
-
Restart
fans.
2)
For
cold
rooms
at
negative
temperatures
with
wrapped
or
absorbent
produce.
-
drainage
(3
to
4
min)
for
the
material
cooling
of
heaters.
-
restart
cooling
with
fans.
Water
defrost
Room at positive temperature
Sequences:
-
Stop
compressor
only
by
pump
down
and
fans
-
Open
water
valve.
-
Stop
water
valve
by
timer
drainage
or
freezing.
-
Restart
fans.
Freezer tunnel
(After removal of produce)
Sequences:
If
defrost
is
initiated:
-
Stop
compressor
only
by
pump
down.
-
Keep
fans
running
until
positive
temperature
is
reached
(initiating
thermostat).
-
Open
timed
delay
water
valve
(10
to
15
mins).
-
Close
and
drain
water
valve
(5
mins).
If
cycle
to
be
re-started:
-
Re-start
fans
-
Re-start
chilling
-
MAINTENANCE
RECOMMENDATIONS
If
the
unit
is
stopped
for
long
periods
of
time,
the
fan
motors
should
be
run
for
at
least
two
hours
each
week.
A
periodic
visual
check
of
the
following
is
recommended:
-
Blocking
and
frosting
of
the
coil
-
Fan
operation
-
Position
of
axial
fans
in
their
collar
-
Possible
movement
of
heaters
-
State
of
each
axial
fan
(tightness
to
shaft,
mechanical
state
of
blades
etc)
-
Water
drain
(U-bend)
