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CHAPTER 5 - TROUBLESHOOTING
5.1 FAULT MESSAGES & COMMON PROBLEMS
When a fault occurs in the boiler plant, the BMS II flashes fault messages at 2-second intervals and the
Fault Alarm (FLT ALARM) relay contacts are closed. The red FAULT indicator on the front panel will also
light. To cancel the alarm (open relay contacts), press the CLEAR key on the BMS II keypad. The FAULT
indicator will turn off, however the fault message will continue to be displayed.
The fault messages shown in Table 5-1 can appear when the BMS II is operating in any of the three basic
modes (Constant Setpoint, Outdoor Reset, or Remote Setpoint).
Table 5-2 lists some common problems that may occur during BMS II operation and provide Probable
Causes and Corrective Action for each listed Probable Cause.
Fault Message
OUTSIDE AIR TEMP
NOT CONNECTED
OUTSIDE AIR TEMP
SENSOR ERROR
HEADER SENSOR
ERROR
INTERLOCK 1 ERROR
INTERLOCK 2 ERROR
Table 5-1. Fault Messages
Description & Possible cause
• Open outside air temp. sensor: resistance greater than 240K ohms (less
than -40°F)
Shorted outside air temp. sensor: resistance less than 1K ohms (greater
than 200°F)
No sensor connected
Note: Displays only in Remote Setpt and Constant
Setpoint modes. I
When in Outdoor Reset Mode, the outside air temperature sensor is either
open, shorted, or not connected.
• Open header sensor: resistance greater than 240K ohms (less than -
40°F)
Shorted header sensor: resistance less than 240 ohms (over 300°F)
Sensor not installed
Interlock 1 is open
Interlock 2 is open
TROUBLESHOOTING
5-1
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