AERCO KC1000 Boiler equipped with Mod-Box Controller - Manual (Page 45)

TROUBLESHOOTING
40
8.2.1 EXHAUST TEMPERATURE
SENSOR
Start the unit and wait for the HI EXHAUST
TEMP. message to display.
1. Using an accurate temperature
measurement device, measure the actual
flue gas temperature. If the measurement
,
taken from the exhaust sensor , is less than
500 o F, and the fault message still does not
clear, shut the unit of f and remove AC
power .
2. Disconnect the exhaust sensor wires from
the field wiring box.
3. Check continuity between the sensor wires.
(ensure that the sensor has cooled below
400
°) If there is continuity replace the
exhaust sensor.
4. If there is no continuity and the exhaust
temperature fault still will not clear, replace
the Annunciator board.
5. If the measured flue gas temperature is
greater than 500 0 F, check combustion
calibration as per Sections 4.2 and 4.3.
8.3. WATER LEVEL FAULT
A LOW WATER LEVEL message indicates that
water level in the unit is too low. Check that the
shut-off valves on the supply and return of the
unit are open and that there is water in the shell.
(Momentarily opening the relief valve and looking
for a strong flow of water will verify that there is
sufficient water level). If there is sufficient water
level, try to reset the unit by pressing the low
water level reset button and the Annunciator
clear button. If the unit fires but the message will
not clear, replace the Annunciator. If the unit
does not fire and the message will not clear
check the following.
8.3.1 Water Level Probe
8.3.2 Wiring & Connections
8.3.3 Water level Circuit
Recommended Troubleshooting Equipment
• Digital Volt/Ohmmeter
8.31 WATER LEVEL PROBE
1. Disconnect the electric power to the unit.
2. Remove the unit cap and remove wire #25
from the water level probe.
WARNING!
THIS WIRE HAS A POTENTIAL OF 12
VAC. BE SURE TO REMOVE POWER
FROM THE UNIT BEFORE
DISCONNECTING OR HANDLING THE
WIRE.
3. Connect an AC voltmeter between wire #25
and the unit frame.
4. Reapply AC power to the unit. The AC
voltmeter should read approximately 12
VAC. If approximately 12 VAC is not read on
the AC voltmeter, proceed to section 8.3.2.
5. If 12 VAC is read on the AC voltmeter,
disconnect power to the unit and ground the
probe to the unit shell.
6. Reconnect AC power to the unit. If the fault
still does not clear, proceed to section 8.3.3.
If the fault clears
, replace the probe.
8.3.2 WIRING AND CONNECTIONS
1. Disconnect AC power to the unit.
2. Remove the unit cap and disconnect wire
#25 from the water level probe and unplug
the 9 pin connector from the control box.
3. Referring to system schematic 161413 in
Appendix H, locate wire #25.
4. Using an ohmmeter check wire #25 for
continuity
5. If wire #25 does not have continuity, repair
as necessary.
6. If wire #25 has continuity, check the probe
end of the wire for a loose connector.
7. Check the pin in the 9 pin connector for
proper insertion or signs of wear.
8. If the connector and pin are okay, reconnect
wire #25 to the water level probe.
9. Reconnect the 9 pin connector to the control
panel.
10. Reconnect electric power to the unit. If the
water level fault still does not clear, see
Section 8.3.3.