LAARS S8Ext - Installation Manual - Manual (Page 31)

Page 31 LAARS Sequencing Controls S8 & S8EXT
TROUBLESHOOTING
TEMPERATURE INPUTS
Display shows Sensor OPEN
Check the sensor is connected and the wires are continuous to the S8. Finally follow the
procedure for Incorrect Temperature Display.
Display shows Sensor SHORT
The S8 sees a short across the input terminals. Remove the wires from the sensor terminals.
The display should change to read OPEN. If it doesn’t, the S8 may be damaged.
Display shows an Incorrect Temperature Display
Remove the wires from sensor terminals. The display should change to read OPEN. If it
doesn’t, the S8 may be damaged. Take an ohm reading across the detached sensor wires. The
ohm reading should correspond to the side chart. If it doesn’t, the sensor may be damaged.
Return Sensor does not Display Temperature
Check the sensor is connected and the wires are continuous to the S8. Finally follow the
procedure for Incorrect temperature display.
CONTROL OPERATION
Too Much Heat
Check if the control has any of the following:
• Domestic Hot Water call - The S8 will raise the temperature of the system to either 200˚F or
Maximum Target on a DHW call.
• Reset Ratio and Offset - If excessive heat occurs only in certain weather conditions, adjust
the Reset Ratio and Offset (See Understanding Operating Concept). If excessive heat occurs
year round, reduce the Offset.
• Unit Mode Settings - The S8 will only sequence boilers their mode is set to Auto or Standby.
Check to see if any boiler stage is set to On.
• Control Settings - The Last Stage Hold will allow only the Lead boiler to stay on for an
additional number of degrees. If the setting is too high, and only the Lead boiler is on, the
system can over heat. Reduce the Last Stage Hold setting.
Too Little Heat
Check if the control has any of the following:
• Reset Ratio and Offset - If reduced heat occurs only in certain weather conditions, adjust the
Reset Ratio and Offset (See Understanding Operating Concept). If reduced heat occurs year
round, increase the Offset.
• Setback and Day/Night Schedule - If reduced heat occurs only during specific hours, check
the Day/Night Schedule and the Setback, Boost, and Boost Period values. Either reduce the
Setback or Boost settings or change the Day and Night Schedules.
• Boiler Mode Settings - The S8 will only modulate boilers their mode is set to Auto or
Standby. Check if any boiler stage is set to Off or Standby.
Units are Short-Cycling
• Minimum Runtime - Increase the Minimum Runtime only if all units tend to short-cycle.
• Last Stage Hold - Increase the Last Stage Hold only if the lead unit tends to short-cycle.
System is Overshooting or Undershooting
• Reaction Time and Minimum Runtime - If the system is overshooting or undershooting, adjust Minimum Runtime or the
Reaction Time. That depends on if the stages are brought on fast and were not allowed to turn off until the Minimum Runtime
elapsed. Or, the stages were brought on slowly, however, were allowed to turn off quickly.
• PID vs OSS - If the application the system is used on requires fast response that the normal PID mode cannot provide, try using
the OSS mode and adjust its parameters according to the system requirements.
Temperature Sensor Chart
TEMPERATURE
(in Degrees °F)
Value
(in Ohms)
-30 117720
-20 82823
-10 59076
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
210 349
220 297
230 253
240 217
250 187