AERCO BMK 1.5 LN July 2011 - Manual (Page 88)

CHAPTER 7: MAINTENANCE
Page 88 of 152 PR2: 05/09/12
Benchmark 1.5LN Low NOx Boiler
Operation and Maintenance Manual
OMM-0041_0D
GF-120
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
TABLE 8-1. BOILER TROUBLESHOOTING (Continued)
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 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.
HIGH WATER
TEMPERATURE
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.