Installation guide
TEMPERATURE
THERMISTORS
Thermistors
are
electronic
devices
which
sense
temperature.
As
the
temperature
increases,
the
resistance
decreases.
Thermistors
are
used
to
sense
outdoor ambient
(OAT)
and
coil
temperature
(OCT).
Refer
to
Fig.
8
for
resistance
values versus
temperature.
If
the
outdoor ambient
or
coil
thermistor
should
fail,
the
control
will
flash
the
appropriate
fault
code
(see
Table
6.)
IMPORTANT:
Outdoor
air
thermistor
and
coil
thermistor
are
factory
mounted
in
the
final
locations.
Check
to
insure
thermistors
are
mounted
properly
per
Fig.
9
and
Fig.
10.
Thermistor
Sensor
Comparison
The
control
continuously
monitors
and
compares
the
outdoor
air
temperature
sensor
and
outdoor
coil
temperature
sensor
to
ensure
proper
operating
conditions.
The
comparison
is:
—
Ifthe
outdoor
air
sensor
indicates
10°F
(5.56°C)
warmer
than
the
coil
sensor
(or)
the
outdoor
air
sensor
indicates
20°F
(11.11°C)
cooler
than
the
coil
sensor,
the
sensors
are
out
of
range.
—
Ifthe
sensors
are
out
of
range,
the
control
will
flash
the
appropriate
fault
code
as
shown
in
Table
6.
—
The
thermistor
comparison
is
not
performed
during
low
ambient
cooling
or
defrost
operation.
Failed
Thermistor
Default
Operation
Factory
defaults
have
been
provided
in
the
event
of
failure
of
outdoor
air
thermistor
and/or
coil
thermistor.
If
the
OAT
sensor
should
fail,
low
ambient
cooling
will
not
be
allowed
and
the
one
minute
outdoor
fan-off
delay
will
not
occur.
If
the
OCT
sensor
should
fail,
low
ambient
cooling
will
not
be
allowed.
OAT
Thermistor
must
be
locked
in
place
with
spherical
nib
end
facing
towards
the
front
of
the
control
box
Status
Codes
Table
6
shows
the
status
codes
flashed
by
the
amber
status
light.
Most
system
problems
can
be
diagnosed
by
reading
the
status
code
as
flashed
by
the
amber
status
light
on
the
control
board.
The
codes
are
flashed
by
a
series
of
short
and
long
flashes
of
the
status
light.
The
short
flashes
indicate
the
first
digit
in
the
status
code,
followed
by
long
flashes
indicating
the
second
digit
of
the
error
code.
The
short
flash
is
0.25
seconds
ON
and
the
long
flash
is
1.0
second
ON.
Time
between
flashes
is
0.25
seconds.
Time
between
short
flash
and
first
long
flash
is
1.0
second.
Time
between
code
repeating
is
2.5
seconds
with
LED
OFF.
EXAMPLE:
3
short
flashes
followed
by
2
long
flashes
indicates
a
32
code.
Table
6
shows
this
to
be
low
pressure
switch
open.
THERMISTOR
CURVE
RESISTANCE
(KOHMS)
0
20
40
(17.77)
(6.67)
(4.44)
(15.56)
TEMPERATURE
°F (°C)
T T T
60 80
100 120
(26.67) (37.78) (48.89)
A08054
Fig.
8
-
Resistance
Values
Versus
Temperature
OAT
Thermistor
must
be
locked
in
place
with
spheri-
cal
nib
end
facing
towards
the
front
of
the
control
box
i
ass
ee
=
=A®
USE
A12263
Fig.
9
-
Outdoor
Air
Thermistor
(OAT)
Attachment
OCT
Thermistor
must
be
VAN
secured
tight
on the
liquid
tube.
gd
A11143
Fig.
10
-
Outdoor
Coil
Thermistor
(OCT)
Attachment
11
-
fia]
z
4
Li
to]
ey,
=
ma
z
4
Li
i]