Troubleshooting – LAARS M4-LHS - Installation Manual User Manual
Page 41
HT# 059295-00
A
M4-LHS installation and Operation Manual
41
TrOuBLESHOOTiNg
SENSOr iNPuTS
Display shows Sensor OPEN or SHOrT
When the display shows sensor OPEN, short the control sensor input terminals. The display
should change to read SHORT. This indicates that the sensor wires are not continuous. If the
display does not SHORT, the M4-LHS may be damaged.
When the display shows sensor SHORT, remove the wires from the sensor terminals. The
display should change to read OPEN. In this case, replace the sensor. Otherwise, if the display
does not show OPEN, the M4-LHS 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-LHS 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.
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
CONTrOL OPEraTiON
No Heat
• Season - Make sure that the Season is set to Winter. See "Season" on page 27 and "Display
• Prove - Even though, the system relay may be energized, the M4-LHS will not energize and
stage relays unless the Prove is shorted. See "Display Messages" on page 38 and "Wiring the
• Shutdown - The M4-LHS will deactivate stage outputs when the Shutdown terminals are
shorted. See "Display Messages" on page 38 and "Wiring the Shutdown, Tstat, or Setback" on
• Tstat - The M4-LHS will deactivate stage outputs when the Tstat terminals are open. See
"Display Messages" on page 38 and "Wiring the Shutdown, Tstat, or Setback" on page 12.
• 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 38 and "Sensor Fault" on page 25.
• System or Outdoor Sensor - If the System or Outdoor sensor reading was higher that the actual
temperature, the M4-LHS might not bring any stage on. Check "Display shows an Incorrect
Temperature" section.
• Outdoor Cutoff - If the Outdoor cutoff was set too low, the building might be allowed to
cool more than is desired. A comfortable setting is between 60°F to 65°F. "Outdoor Cutoff
Too Much Heat
• Indirect Domestic Hot Water call - The M4-LHS 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 5. If excessive heat occurs year
round, reduce the Offset.
• Boiler Mode Settings - The M4-LHS 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 39.
• 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 32.