Specifications

I-.l
CHECKING
OPERATIOT\f
-
(A'
Moders)
The
following
general
information
ex-
plains
several
method for
checking oper-
ation of the refrigeration
system. This
information
applies to all systems
covered
in
this manual.
The
correct operation
of a refrigeration
system is
dependent upon the
proper
functioning
of each of the
parts
comprising
the system. lf the
system does
not operate
properly
(long
run
periods,
warmer than
normal
temperatures),
the trouble
may be
caused
by one of the following
conditions.
RESTRICTED
CAPILLARY
TUBE
The
opening
of a capillary
tube is
about
the
same
diameter as the
period
at the
end of this
sentence. This
should indicate
that
it doesn't
take much
to restrict
this
tube. lt
should also tell
you
to
use care
when
any service
procedures
involve
moving
or
touching
the
capillary
tube. A
very
slight
kink
can
cause
a complete re-
striction
of
the tube.
Restrictions
of the
capillary tube
may be
caused
by:
(1)
moisture
freeze-up,
(2)
tor-
eign
particles
lodged
in the tube,
or
(3)
a
bend
or
kink.
lf the
capillary tube
is restricted,
there
will
be
a
noticeable
lack of frost
on
all of the
cooling
surfaces; the
compressor
may
op-
erate for
a short
period
of time
and then
cycle
on the
overload. Because
some mo-
dels can hold the
entire
charge in
the
condenser,
the compressor
may run con-
tinuously
and
definite
vacuum
will be no-
ticed
in the low
side.
When moisture
freeze-up
causes
a restriction,
it usually
occurs
at the
outlet
end of the
capillary
tube.
Normally,
a frost
build-up
can
be
detected in
this
area,
but
insulation
wrapped
around the
tubing may
conceal
or limit the
amount
of frost
accumulation.
Expose
the discharge
end of the capillary
and apply heat
at this
point.
lf there
is
enough head
pressure,
and if the
re-
striction
is caused
by moisture
freeze-up,
you
will
be able to
hear a
gurgling
noise
as the
heat releases
the ref
rigerant
through the
tubing.
It is
possible
that this
moisture will
be ab-
sorbed
by the
drier and remedy the
trou-
ble. However, if the
freeze-up recurs,
you
must replace
the drier.
A kink in
the capillary
tube will reveal
about the
same symptom
as a moisture
freeze-up
except for the
accumulation
of
frost.
Check the
entire length
of
the
capil-
lary
tube and, if
possible,
straighten the
kink to
relieve the
restrictions.
Check the
unit operation to
see if
you
have helped
the
situation. lf the trouble
persists,
re-
place
the
defective
part.
lf
the freeze-up
condition
does not
exist
and
there
is
not
a
kink,
you
can
assume
that
a foreign
particle
is
causing the re-
strictions
--
the
only remedy
in this
case
is
to replace
the restricted
part.
PARTIAL
RESTRICTION
IN LOW
SIDE
TUBING
Bent tubing,
foreign
matter,
or moisture in
the
system may
cause
a
partial
restriction
in
the low
side tubing. This
is usually
in-
dicated
by
frost-free
tubing
between the
restriction
and the
capillary
tube
and by
f rost-covered
tubing
between
the re-
striction
and
the
suction line.
The
re-
striction
acts like
a second
capillary tube,
increasing
the
pressure
ahead
of
it
(warming)
and
decreasing the
pressure
beyond it
(cooling).
To confirm
the
exist-
ence
of a restriction
in the low
side tubing,
perform
operational
pressure
checks.
3-5