Watts AERCO Benchmark 2.0 LN Operating & Maintenance Instructions page 58

TROUBLESHOOTING
FAULT INDICATION
continued 3. Device proving switch hooked to
LINE VOLTAGE 1. Line and Neutral switched in AC
OUT OF PHASE
2. Incorrect power supply transformer
LOW GAS 1. Incorrect supply gas pressure.
PRESSURE
2. Defective Low Pressure Gas Switch
LOW WATER 1. Insufficient water level in system
LEVEL
2. Defective water level circuitry.
3. Defective water level probe.
MODBUS COMM 1. Boiler not seeing information from
FAULT
PRG SWTCH CLOSED 1. A/F Valve rotated open to purge and
DURING IGNITION
8-7
TABLE 8-1. BOILER TROUBLESHOOTING – Continued
PROBABLE CAUSES
interlocks is not closed.
Power Box.
wiring.
modbus network
did not rotate to ignition position
CORRECTIVE ACTION
3. Check that proving switch for any device hooked to the interlock
circuit is closing and that the device is operational.
1. Check hot and neutral in AC Power Box to ensure they are not
reversed
2. Check transformer wiring, in AC Power Box, against the power
box transformer wiring diagram to ensure it is wired correctly
1. Measure gas pressure upstream of the supply gas regulator with
the unit firing. Ensure it is at least 5.3" WC (5.5" WC for IRI). For
Benchmark 2.0 Low NOx boilers configured for De-Rated
capacity (see para. 2.4.1), ensure gas pressure upstream of the
supply gas regulator, with the unit firing, is at least 4.0" W.C.
(4.2" W.C. for IRI).
2. Measure gas pressure at the low gas pressure switch, if it is
greater than 4.4" WC measure continuity across the switch and
replace if necessary. For Benchmark 2.0 Low NOx boilers
configured for De-Rated capacity (see para. 2.4.1), if measured
gas pressure at the low gas pressure switch is greater than 3.6"
W.C., measure continuity across the switch and replace if
necessary.
1. Check system for sufficient water level.
2. Test water level circuitry using the Control Box front panel LOW
WATER TEST and RESET buttons. Replace water level
circuitry if it does not respond.
3. Check continuity of probe end to the shell, change probe if there
is no continuity.
1. Check network connections. If fault persists, contact qualified
Service Personnel.
1. Start the unit. The Air/Fuel Valve should rotate 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 Control Box. Refer fault to qualified service personnel.