Page 26
LAARS Heating Systems
TROUBLESHOOTING
No Display, or Display of
888
Check the 120VAC power input to the SC. Turn power to the SC off and back on.
TEMPERATURE INPUTS
Display shows
OPn
First check the dip switch (see pg. 4 ) to be sure the SC is confi gured to read a temperature
input. If the dip switch is correct, then the SC does not register that a sensor is connected.
Check that the wires from the sensor are continuous to the SC. Then follow the procedure for
Incorrect Temperature Display.
Display shows
SHt
The SC sees a short across the input terminals. Remove the wires from the
TEMP
(
1
&
2
)
inputs. The display should change to read
OPn
. If it doesn’t, the SC may be damaged.
Display shows an Incorrect Temperature Display
Remove the wires from the
TEMP
(
TEMP
TEMP 1
and
2
) inputs. The display should change to read
OPn
.
If it doesn’t, the SC may be damaged. Take an ohm reading across the detached sensor wires.
The ohm reading should correspond to the chart at right. If it doesn’t, the sensor may be
damaged.
Outdoor Temperature Display shows
OPn
Check the wires from the outdoor sensor are continuous to the SC. Then follow the procedure
for Incorrect Outdoor Temperature Display.
Outdoor Temperature Display shows
SHt
The SC sees a short across the input terminals. Remove the wires from the
OUTDOOR
(
11
and
12
and
and ) inputs. The display should change to read
OPn
. If it doesn’t, the SC may be
damaged.
Outdoor Temperature Display shows an Incorrect Reading
Remove the wires from the
OUTDOOR
(
11
and
12
) inputs. The outdoor temperature display
should change to read
OPn
. If it doesn’t, the SC may be damaged. Take an ohm reading
across the detached sensor wires. The ohm reading should correspond to the chart on the
right. If it doesn’t, the sensor may be damaged.
EXTERNAL SET POINT INPUT
Set Point changes when the knob is rotated
Check the dip switch (pg. 4).
Set Point always reads
OFF
Check that the wiring is appropriate for the application (see pg. 23). Then use an ampmeter to measure the 4-20mA input. If the
input is below 3.9mA or above 20.1mA, the Set Point will always be
OFF
.
LEAD STAGE
There is no green lead stage light on
Check the 120VAC power input to the SC. Turn power to the SC off and back on. If more than one lead stage LED lights, the
unit may be damaged.
TEMPERATURE
(in Degrees F)
Value
(in Ohms)
0
42683
10
31215
20
23089
25
19939
30
17264
35
14985
40
13040
45
11374
50
9944
55
8714
60
7653
70
5941
80
4649
90
3667
100
2914
110
2332
120
1879
130
1524
140
1243
150
1021
160
842
170
699
180
583
190
489
200
412
