LAARS SC 12 - Install and Operating Manual - Manual (Page 26)

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