Watts AERCO Benchmark BMK750 Operation And Service Manual page 150

Benchmark with Edge [I]: Operation-Maintenance Manual
SECTION 9 – TROUBLESHOOTING
TABLE 9-1: Boiler Troubleshooting Procedures
Fault Probable Causes
TEMP
Incorrect PID settings.
2.
SWITCH
OPEN
Faulty shell temperature
3.
sensor.
Unit in Manual mode.
4.
Unit setpoint is greater than
5.
Over Temperature switch
setpoint.
System flow rate changes are
6.
occurring faster than units can
respond.
See HIGH WATER
1.
TEMPERATURE SWITCH
HIGH WATER
OPEN.
TEMPERATU
RE
Temp HI Limit setting is too
2.
low.
Communication fault has
1.
occurred between the PMC
IGN BOARD
board and Ignition/Stepper
COMM
(IGST) board.
FAULT
32 Pin Ribbon cable defective.
2.
Air/Fuel Valve not rotating.
1.
IGN
SWITCH
CLOSED
DURING
Defective or shorted switch.
2.
PURGE
OMM-0145_A99 • GF-218 • Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST
9/18/2019
Corrective Action
Check PID settings (Advanced Setup →
2.
Performance → Temperature Control, first 3
items). If the settings have been changed,
record the current readings then reset to
default values.
Using the resistance charts in Section 2 of the
3.
Benchmark 750-6000 with Edge [i]: Reference
Manual (OMM-0146, GF-219) measure the
resistance of Shell sensor and BTU sensor at
a known water temperature.
If unit is in Manual mode, switch to Auto
4.
mode (Diagnostic → Manual Mode).
Check setpoint of unit and setpoint of
5.
Temperature switch; Ensure that the
temperature switch is set higher than the unit's
setpoint.
If the system is a variable flow system,
6.
monitor system flow changes to ensure that
the rate of flow change is not faster than what
the units can respond to.
See HIGH WATER TEMPERATURE SWITCH
1.
OPEN.
Check Temp HI Limit setting.
2.
Press CLEAR button and restart unit. If fault
1.
persists, contact qualified Service Personnel.
Replace 32 Pin Ribbon cable.
2.
Start the unit. The Air/Fuel Valve should rotate
1.
to the purge (open) position. If the valve does
not rotate at all or does not rotate fully open,
check the Air/Fuel Valve calibration. If
calibration is okay, the problem may be in the
Air-Fuel Valve or the Edge [i] Controller. Refer
to qualified service personnel.
If the Air/Fuel Valve does rotate to purge,
2.
check the ignition switch for continuity
between the N.O. and COM terminals. If the
switch shows continuity when not in contact
with the cam replace the switch.
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