AERCO KC1000 Low NOx Water Heater July 2011 - Manual (Page 71)

TROUBLESHOOTING
7-7
KC1000 WATER HEATER TROUBLESHOOTING TABLE – Continued
FAULT INDICATION PROBABLE CAUSES CORRECTIVE ACTION
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 or incorrectly
sized Gas Supply
Regulator.
3. Defective Low
Pressure Gas Switch
1. Measure gas pressure upstream of the supply
gas regulator with the unit firing ensure it is 14”
WC or greater.
2. Measure gas pressure downstream of the supply
regulator with unit firing and adjust the gas supply
regulator to increase the outlet gas pressure; if
outlet gas pressure cannot be increased, check
the sizing of the Supply regulator.
3. Measure gas pressure at the low gas pressure
switch, if it is greater than 5” WC 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. Water Heater 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
2. Defective or shorted
switch.
3. Switch wired
incorrectly.
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.
2. If the Air/Fuel Valve does rotate to the ignition
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).
3. If switch is wired correctly, replace switch.