Watts AERCO Benchmark 2.0LN, Operating & Maintenance Instructions

Page: 58 / 101

TROUBLESHOOTING
8-7
TABLE 8-1. BOILER TROUBLESHOOTING – Continued
FAULT INDICATION PROBABLE CAUSES CORRECTIVE ACTION
continued 3. Device proving switch hooked to
interlocks is not closed.
3. Check that proving switch for any device hooked to the interlock
circuit is closing and that the device is operational.
LINE VOLTAGE
OUT OF PHASE
1. Line and Neutral switched in AC
Power Box.
2. Incorrect power supply transformer
wiring.
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
LOW GAS
PRESSURE
1. Incorrect supply gas pressure.
2. Defective Low Pressure Gas Switch
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.
LOW WATER
LEVEL
1. Insufficient water level in system
2. Defective water level circuitry.
3. Defective water level probe.
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.
MODBUS COMM
FAULT
1. Boiler not seeing information from
modbus network
1. Check network connections. If fault persists, contact qualified
Service Personnel.
PRG SWTCH CLOSED
DURING IGNITION
1. A/F Valve rotated open to purge and
did not rotate to ignition position
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.