Aerco KC Series Installation, Operation & Maintenance Instructions Manual page 45

5. Referring to system schematic 161412 in
the Appendix, locate and check continuity in
wires #20 and #32 from the fifteen pin
connector through the switch and back to
the connector.
6. If there is no continuity
connectors at the switch end of the wires.
Check the pins in the 15-pin connector for
proper insertion or signs of wear.
7. If the 15-pin connector and the switch
connections are okay, reconnect the 15-pin
connector to the control panel. Restore
electric power.
If the gas pressure fault does not clear it will be
necessary to troubleshoot the control panel.
Contact a qualified service technician or your
local AERCO representative for more
information.
7.2 HIGH EXHAUST TEMPERATURE
A HI EXHAUST TEMP message indicates that
the exhaust temperature has exceeded 500
This fault only indicates on the display and
WILL NOT SHUT DOWN the unit. The fault
LED and the fault relay will trip indicating the
fault.
A high exhaust temperature is an indication that
the unit has a carbon coating on the fireside of
the heat exchanger exhaust tubes. This
condition results in a loss of heat transfer and
therefore high exhaust temperatures. Carbon
buildup can be due to due to improper
combustion calibration, a defective air or fuel
component, improper stop\start levels or
improper supply gas pressure. The unit should
be combustion calibrated to determine if one of
the above is responsible. Refer to section 4.4
for combustion calibration, or contact your local
AERCO representative further assistance.
7.2.1 Exhaust Temperature Sensor
7.2.2 Wiring & Connections
Recommended Troubleshooting Equipment
Digital Ohmmeter
Digital Temperature Meter
7.2.1 EXHAUST TEMPERATURE
SENSOR
1. Start the unit and wait for the HI EXHAUST
TEMP. message to display
,
check for loose
o
F.
TROUBLESHOOTING
2. Using an accurate temperature
measurement device, measure the actual
flue gas temperature. If the exhaust sensor
measurement is less than 500
pressing the clear button does not clear the
fault message, shut the unit off and remove
AC power from the unit.
3. Disconnect the exhaust sensor wires from
the field wiring box.
4. Check continuity between the sensor wires.
(ensure that the sensor has cooled below
400°). If there is continuity
exhaust sensor.
5. If there is no continuity and the exhaust
temperature fault will not clear, combustion
calibrate the unit as per Section 4.4.
7.3 LOW WATER LEVEL
A LOW WATER LEVEL message indicates that
water level in the unit is too low. Check that the
shutoff 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
the unit shell has sufficient water level). If the
unit has water 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.
7.3.1 Water Level Probe
7.3.2 Wiring & Connections
7.3.3 Water level Circuit
Recommended Troubleshooting Equipment
•
Digital Volt/Ohmmeter
7.3.1 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.
3. Connect an AC voltmeter between wire #25
and the unit frame.
4. Reapply electrical 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 7.3.2.
40
o
F, and
,
replace the