AERCO BMK 1.5 LN Dual Fuel Feb 2013 - Manual (Page 94)

CHAPTER 8: TROUBLESHOOTING GUIDE
Page 94 of 162 PR2: 05/09/12
Benchmark 1.5LN Dual-Fuel Low NOx Boiler
Operation and Maintenance Manual
OMM-0041_0C
GF-121
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
FAULT
INDICATION
PROBABLE CAUSES CORRECTIVE ACTION
HIGH GAS
PRESSURE
1. Incorrect supply gas pressure.
2. Defective SSOV Actuator.
3. Defective 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 Actuator cannot be lowered,
to 1.5” W.C. using the gas pressure adjustment screw (see para. 4.3, step
10), the SSOV Actuator 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. Ensure that the gas pressure snubber is installed at the
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/AERCO Control
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/ACS for changes to PID default values, correct as
necessary.
7. If system pump is controlled by Energy Management System other than
BMS/ACS or pumps are individually controlled by boiler, check to see if
there are flow switches interlocked to the BMS/ACS 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.
HIGH WATER
TEMPERATU
RE
1. See HIGH WATER TEMPERATURE
SWITCH OPEN.
2. Temp HI Limit setting is too low.
1. See HIGH WATER TEMPERATURE SWITCH OPEN.
2. Check Temp HI Limit setting.
TABLE 8-1. BOILER TROUBLESHOOTING (Continued)