AERCO BMK 2.0 LN Natural Gas 2008 - Manual (Page 54)

TROUBLESHOOTING
TABLE 8-1. BOILER TROUBLESHOOTING
FAULT INDICATION PROBABLE CAUSES TROUBLESHOOTING/CORRECTIVE ACTION
AIRFLOW FAULT
DURING IGNITION
1. Blower stopped running due to thermal
or current overload
2. Blocked Blower inlet or inlet ductwork
3. Blocked Blower proof switch
4. Defective Blower proof switch
5. Defective blocked-air inlet switch
6. Loose temperature transmitter to
VFD’s analog input wire connection
7. Loose temperature sensor to
temperature transmitter wire
connection.
8. Defective temperature transmitter
9. Defective temperature sensor
10. Loose wire connection between the 4-
20 mA signal from I/O box to VFD
analog input
11. Defective I/O box
12. Wrong 4-20 mA output selection on
the control box
13. Defective air-fuel valve potentiometer
14. Missing VFD logic stick
15. Incorrect or missing analog output
from VFD to blower.
1. Check combustion blower for signs of excessive heat or high
current drain that may trip thermal or current overload devices.
2. Inspect the inlet to the combustion blower including any ductwork
leading up to the combustion blower for signs of blockage.
3. Remove the Blower proof switch and inspect for signs of
blockage, clean or replace as necessary.
4. Measure the Blower proof switch for continuity with the
combustion blower running. If there is an erratic resistance
reading or the resistance reading is greater than zero ohms,
replace the switch.
5. Measure the blocked-air inlet switch for continuity with the
combustion blower running. If there is an erratic resistance
reading or the resistance reading is greater than zero ohms,
replace the switch.
6. Check the actual inlet air temperature and measure voltage at
temperature transmitter and VFD analog input. Verify that the
voltage conforms to Table 8-3 for the inlet air temperature.
7. Refer to CORRECTIVE ACTION 7 and verify that the resistance
conforms to Table 8-3.
8. See CORRECTIVE ACTION 7.
9. See CORRECTIVE ACTION 8.
10. Measure amperage at the I/O box output and VFD analog input,
4mA equates to 0% fire rate and 20 mA equates to 100% fire
rate
11. See CORRECTIVE ACTION 11.
12. Check C-More configuration menu, mA OUT – Fire Rate should
be selected
13. Check air fuel valve position at 0%, 50% and 100% fire rates,
the position on the c-more barograph should match the valve
14. Confirm that the logic stick is securely inserted in the VFD
15. Measure DC voltage between VFD terminals B1 and T1 (see
Figure 8-4). Voltage should be between 2.0 and 5.0 VDC.
8 -2