Watts Aerco Benchmark OMM-0117 Operation And Maintenance Manual page 68

Benchmark 5000-6000 Operation & Maintenance Manual
SECTION 5 – TROUBLESHOOTING GUIDE
TABLE 5-1: Boiler Troubleshooting Procedures
FAULT
INDICATION
Incorrect supply gas pressure.
1.
Defective SSOV Actuator.
2.
GAS
PRESSURE
FAULT
(Due to High
Gas Pressure)
Defective High Gas Pressure switch.
3.
Faulty Water temperature switch.
1.
Incorrect PID settings.
2.
Faulty shell temperature sensor.
3.
Unit in MANUAL mode.
4.
HIGH WATER
Unit setpoint is greater than Over Temperature
5.
TEMP
switch setpoint.
SWITCH OPEN
System flow rate changes are occurring faster
6.
than units can respond.
Refractory failure.
7.
VFD is in "Local" mode, or voltage dropped
8.
below threshold.
OMM-0118_B • GF-203 • 5/9/2019
PROBABLE CAUSES
Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST
CORRECTIVE ACTION
Check to ensure gas pressure at inlet of SSOV does not exceed
1.
14" W.C. (3487 Pa)
If NATURAL GAS supply pressure downstream of SSOV Actuator
2.
cannot be lowered using the gas pressure adjustment screw to the
range specified in the Benchmark 5000 – 6000 Installation and
Startup Guide, OMM-0117 (GF-202), Section 4.5.1, Table 4-1
(Natural Gas) or Section 4.5.2, Table 4-4 (Propane), the SSOV
Actuator may be defective.
Remove the leads from the High Gas Pressure switch. Measure
3.
continuity across the common (C) and normally closed (NC)
terminals with the unit not firing. Replace the switch if continuity
does not exist.
Test the temperature switch to insure it trips at its actual water
1.
temperature setting.
Check PID settings against menu default settings in Section 2,
2.
above. If the settings have been changed, record the current
readings then reset them to the default values.
Using the resistance charts in the Appendix C, Measure the
3.
resistance of Shell sensor and BTU sensor at a known water
temperature.
If unit is in MANUAL mode, switch to AUTO mode.
4.
Check setpoint of unit and setpoint of Temperature switch; Ensure
5.
that the temperature switch is set higher than the unit's setpoint.
If the system is a variable flow system, monitor system flow
6.
changes to ensure that the rate of flow change is not faster than
what the units can respond to.
Refractory temperature switches on the end plates are in series
7.
with the water temperature limit control to shut down the boiler if
the end plates get too hot. Replace the refractory at the hottest end
plate.
Check incoming voltage, set VFD to "Remote" mode.
8.
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