Rev
B
MN301530
13
of
14
APPENDIX
Step
Nine
Relay
Latch
Logic
(Relay
2,
LC82
Series
only):
This
relay
is
primarily
a
flow/no
‐
flow
relay.
However,
when
used
as
a
level
relay,
it
can
either
be
an
independent
relay
(high
or
low
level
alarm)
or
a
latching
relay
(automatic
fill
or
empty)
with
latch
ON.
With
Latch
OFF,
the
relay
will
only
respond
to
the
Input
2A.
Input
2B
will
be
ignored.
This
configuration
is
ideal
for
alarming,
such
as
flow,
no
‐
flow,
leak
detection,
high
level
or
low
level.
When
the
Latch
switch
is
ON,
Relay
2
requires
that
both
Inputs
2A
and
2B
to
be
in
the
same
state
before
the
relay
will
switch.
In
an
auto
fill
application,
when
the
bottom
switch
is
dry
(top
switch
is
also
dry)
the
relay
will
energize.
The
relay
will
remain
in
an
energized
state
until
the
top
switch
becomes
wet
(bottom
switch
is
also
wet).
At
this
point,
the
relay
will
de
‐
energize
and
remain
de
‐
energized
until
the
bottom
switch
becomes
dry
again.
The
same
logic
applies
for
auto
empty
applications.
The
only
change
is
that
the
relay
will
energize
when
the
top
is
wet
(bottom
is
also
wet)
and
de
‐
energize
when
the
bottom
is
dry
(top
is
also
dry).
In
both
scenarios,
when
the
level
is
between
the
two
sensors,
the
relay
will
not
change
state,
regardless
of
is
the
liquid
is
rising
or
falling.
This
logic
is
ideal
for
the
controlling
of
liquid
between
to
unique/different
set
points.
The
differential
is
controlled
by
the
location
of
the
two
sensors.
Caution:
Some
sensors
may
have
their
own
inverting
capability
(wired
NO
or
NC).
This
will
change
the
logic
of
the
invert
switch.
Check
your
system
design.
Invert
OFF
Latch
OFF
Input
2A
Input
2B
Relay
ON
OFF
No
Effect
No
Effect
ON
OFF
Invert
OFF
Latch
OFF
Input
2A
Input
2B
Relay
ON
OFF
No
Effect
No
Effect
OFF
ON
With
Latch
ON,
the
relay
will
actuate
when
Input
2A
and
Input
2B
are
in
the
same
condition.
The
relay
will
not
change
its
condition
until
both
inputs
reverse
their
state.
Invert
OFF
Latch
ON
Input
2A
Input
2B
Relay
ON
OFF
ON
OFF
ON
ON
OFF
OFF
ON
No
Change
No
Change
OFF
Invert
ON
Latch
ON
Input
2A
Input
2B
Relay
ON
OFF
ON
OFF
ON
ON
OFF
OFF
OFF
No
Change
No
Change
ON
