LAARS M4-Ext - Installation Manual - Manual (Page 26)

Page 26 LAARS Heating Systems
TROUBLESHOOTING
TEMPERATURE INPUTS
Display shows Sensor OPEN
Check the sensor is connected and the wires are continuous to the M4. Finally follow the
procedure for Incorrect Temperature Display.
Display shows Sensor SHORT
The M4 sees a short across the input terminals. Remove the wires from either the SYSTEM
TEMP or OUT TEMP terminals (whichever is reading SHORT). The display should change to
read OPEN. If it doesn’t, the M4 may be damaged.
Display shows an Incorrect Temperature Display
Remove the wires from either the SYSTEM TEMP or OUT TEMP terminals (whichever is
reading incorrectly). The display should change to read OPEN. If it doesn’t, the M4 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.
CONTROL OPERATION
No Heat
•
(Check Diagram on next page)
Too Much Heat
Check if the control has any of the following:
•
Domestic Hot Water call - The M4 will raise the temperature of the system to either 200˚F or
Maximum Water Temperature on a DHW call, connected to terminals 29 and 30. Check to see
if there is a call for DHW and the length of time it lasts.
• Reset Ratio and Offset - If excessive heat occurs only in certain weather, adjust the Reset
Ratio and Offset (See Understanding Operating Concept). If excessive heat occurs year round,
reduce the Offset.
• Boiler Mode Settings - The M4 will only modulate boilers their mode is set to Auto or
Standby. Check to if any boiler stage is set to Manual or 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, 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 values. Either reduce the Setback setting or change
the Day and Night Schedules.
• Boiler Mode Settings - The M4 will only modulate boilers their mode is set to Auto or Standby. Check to if any boiler stage is
set to Manual, Off, or Standby.
Boilers are Short-Cycling
•
Lag Delay - Increase the Lag Delay only if all boilers tend to short-cycle.
• Last Stage Hold - Increase the Last Stage Hold only if the lead boiler tends to short-cycle.
System is Overshooting or Undershooting
•
Gain - If the system is overshooting reduce the Gain.
• Gain - If the system is undershooting increase the Gain.
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