Watts AERCO Benchmark BMK750 Operation And Service Manual page 152

Benchmark with Edge [I]: Operation-Maintenance Manual
SECTION 9 – TROUBLESHOOTING
TABLE 9-1: Boiler Troubleshooting Procedures
Fault Probable Causes
OUT OF
Incorrect power supply
2.
PHASE
transformer wiring.
Incorrect supply gas pressure.
1.
LOW GAS
Defective Low Gas Pressure
2.
PRESSURE
switch.
Insufficient water level in
1.
system.
Defective water level circuitry.
2.
LOW
WATER
LEVEL
Defective water level probe.
3.
MODBUS
Unit not seeing information from
COMMFAU
Modbus network.
LT
A/F Valve rotated open to
1.
purge and did not rotate to
ignition position.
PRG
SWTCH
CLOSED
Defective or shorted switch.
2.
DURING
IGNITION
Switch wired incorrectly.
3.
OMM-0145_A99 • GF-218 • Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST
9/18/2019
Corrective Action
Check transformer wiring, in AC Power Box,
2.
against the power box transformer wiring
diagram to ensure it is wired correctly.
Measure gas pressure upstream of the SSOV
1.
Actuator(s) with the unit firing. Ensure it is
above the value in Table 4-2 (Natural Gas) or
Table 4-5 (Propane).
Measure gas pressure at the Low Gas
2.
Pressure switch. If it is greater than 1 inch
above the Low Gas Pressure switch setting
in Table 4-2 (Natural Gas) or Table 4-5
(Propane), measure continuity across the
switch and replace if necessary.
Check system for sufficient water level.
1.
Test water level circuitry using the Low Water
2.
TEST and RESET buttons on the Controller's
front panel. Replace water level circuitry if it
does not respond.
Check continuity of probe end to the shell,
3.
change probe if there is no continuity.
Check network connections. If fault persists,
contact qualified Service Personnel.
Start the unit. The Air/Fuel Valve should rotate
1.
to the purge (open) position, then back to
ignition position (towards closed) during the
ignition cycle. If the valve does not rotate back
to the ignition position, 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 fault to qualified
service personnel.
If the Air/Fuel Valve does rotate to the ignition
2.
position, check the purge switch for continuity
between the N.O. and COM terminals. If the
switch shows continuity when not in contact
with the cam, check to ensure that the switch
is wired correctly (correct wire numbers on the
normally open terminals).
If the switch is wired correctly, replace the
3.
switch.
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