LAARS M4-Ext - Installation Manual - Manual (Page 33)

Installation Manual 33
TROUBLESHOOTiNg
SENSOR iNPUTS
display shows Sensor OPEN or SHORT
When OPEN, Check the sensor is connected and the wires are continuous to the M4-CNC.
Finally follow the procedure for Incorrect Temperature Display. When SHORT Remove the
wires from the sensor terminals. The display should change to read OPEN. If it does not, the
M4-CNC may be damaged. When OPEN short the wires from the sensor terminals. The display
should change to read SHORT. If it does not, the M4-CNC may be damaged.
display shows an incorrect Temperature
Remove the wires from the sensor terminals. The display should change to read OPEN. If it
does not, the M4-CNC may be damaged. Take an ohm reading across the detached sensor wires.
The ohm reading should correspond to the Temperature sensor Chart. If it does not, the sensor
may be damaged.
CONTROL OPERATiON
No Heat
• Season - Make sure that the Season is set to Winter. See "Season" on page 22 and "Display
Messages" on page 30.
• Prove - Even though, the system relay may be energized, the M4-CNC will not energize and
stage relays unless the Prove is shorted. See "Display Messages" on page 30 and "Wiring the
Prove" on page 12.
• Shutdown - The M4-CNC will deactivate stage outputs when the Shutdown terminals are
shorted. See "Display Messages" on page 30 and "Wiring the Shutdown, Tstat, or Setback" on
page 11.
• Tstat - The M4-CNC will deactivate stage outputs when the Tstat terminals are open. See
"Display Messages" on page 30 and "Wiring the Shutdown, Tstat, or Setback" on page 11.
• Sensor Fault - When the Sensor Fault is set to All Off in the startup menu, the System sensor
fault (in all Sensor Type modes) or the Outdoor sensor fault (in Reset mode) will de-energize all
stage relays. See "Display Messages" on page 30 and "Sensor Fault" on page 20.
• System or Outdoor Sensor - If the System or Outdoor sensor reading was higher that the actual
temperature, the M4-CNC might not bring any stage on. Check "Display shows an Incorrect
Temperature" section.
Too Much Heat
• Domestic Hot Water call - The M4-CNC will raise the temperature of the system to the DHW
Set Point 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 conditions, adjust the
Reset Ratio and Offset. See "Outdoor Reset Concept" on page 7. If excessive heat occurs year
round, reduce the Offset.
• Boiler Mode Settings - The M4-CNC will only controls boilers their mode is set to Auto or
Standby. Check if any boiler stage is set to Manual or On. See "Mode" on page 31.
• 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. See"Last Stage Hold" on page 25.
Too Little Heat
• Reset Ratio and Offset - If reduced heat occurs only in certain weather conditions, adjust the
Reset Ratio and Offset (See "Outdoor Reset Concept" on page 7). 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. Then, reduce the Setback setting. See "Setback"
on page 24.
• Boiler Mode Settings - The M4-CNC will only control boilers their mode is set to Auto or
Standby. Check if any boiler stage is set to Manual, Off, or Standby. See "Mode" on page 31.
Boilers are Short-Cycling
• Lag Delay - Increase the Lag Delay only if modulating boilers tend to short-cycle.
• Minimum Runtime - Increase the Minimum Runtime only if staging 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. See "Gain" on page 26.
• Gain - If the system is undershooting increase the Gain.
Temperature Sensor Chart
TEMPERATURE value
(in Ohms) ° F ° C
OPEN 150000
-30 -34 117720
-20 -29 82823
-10 -23 59076
0 -18 42683
10 -12 31215
20 -7 23089
25 -4 19939
30 -1 17264
35 2 14985
40 4 13040
45 7 11374
50 10 9944
55 13 8714
60 16 7653
70 21 5941
80 27 4649
90 32 3667
100 38 2914
110 43 2332
120 49 1879
130 54 1524
140 60 1243
150 66 1021
160 71 842
170 77 699
180 82 583
190 88 489
200 93 412
210 99 349
220 104 297
230 110 253
240 116 217
250 121 187
SHORT 100
LAARS Modulating Controls M4 & M4-EXT
HT# 059104-00 B