AERCO BMK 1.5 LN Dual Fuel June 2010 - Manual (Page 68)

TROUBLESHOOTING
TABLE 8-1. BOILER TROUBLESHOOTING – Continued
FAULT
INDICATION
PROBABLE CAUSES CORRECTIVE ACTION
HIGH EXHAUST
TEMPERATURE 1. Defective exhaust sensor.
2. Carboned heat exchanger due to
incorrect combustion calibration
1. Measure the actual exhaust temperature and continuity of the exhaust
sensor. If the exhaust temperature is less than 475 o F and the
exhaust sensor shows continuity replace the sensor.
2. If exhaust temperature is greater than 500 o F, check combustion
calibration. Calibrate or repair as necessary.
HIGH GAS
PRESSURE
1. Incorrect supply gas pressure.
2. Defective SSOV Supply Regulator.
3. Defective natural gas or propane high
gas pressure ‘switch.
4. Gas pressure snubber not installed.
1. Check to ensure gas pressure at inlet of SSOV is 2 psig maximum.
2. If gas supply pressure downstream of SSOV cannot be lowered, to 3”
W.C. (see para. 4.3, step 12), the SSOV Regulator may be defective.
3. Remove the leads from the high gas pressure switch and measure
continuity across the common and normally closed terminals with the
unit not firing. Replace the switch if it does not show continuity.
4. See Figure 8-1 at end of Chapter. Ensure that the gas pressure
snubber is installed at the appropriate high gas pressure switch.
HIGH WATER TEMP
SWITCH OPEN
1. Faulty Water temperature switch.
2. Incorrect PID settings.
3. Faulty shell temperature sensor.
4. Unit in Manual mode
5. Unit setpoint is greater than Over
Temperature Switch setpoint.
6. Boiler Management System PID or other
settings not correctly setup.
7. No interlock to boiler or BMS to disable
boiler(s) in event that system pumps
have failed.
8. System flow rate changes are occurring
faster than boilers can respond.
1. Test the temperature switch to insure it trips at its actual water
temperature setting.
2. Check PID settings against Menu Default settings in the Appendix. If
the settings have been changed, record the current readings then
reset them to the default values.
3. Using the resistance charts in the Appendix C, Measure the
resistance of Shell sensor and BTU sensor at a known water
temperature.
4. If unit is in Manual Mode switch to Auto Mode.
5. Check setpoint of unit and setpoint of Temperature Switch; Ensure
that the temperature switch is set higher than the unit’s setpoint.
6. Check the BMS for changes to PID default values, correct as
necessary.
7. If system pump is controlled by Energy Management System other
than BMS or pumps are individually controlled by boiler, check to see
if there are flow switches interlocked to the BMS or boiler.
8. If the system is a variable flow system, monitor system flow changes
to ensure that the rate of flow change is not faster than what the
boilers can respond to.
8-6