AERCO KC1000 Heater w/Mod-Box Controller - Manual (Page 47)

TROUBLESHOOTING
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7. Reset the unit and if necessary, the upper
over-temperature limit switch. If the unit will
not reset proceed to section 7.4.2.
7.4.2. OVER TEMPERATURE LIMIT
SWITCHES
1. Disconnect electrical power to the unit.
2. Raise the temperature limit switch setpoint a
minimumof 10
0
F above the actual discharge
water temperature.
3. Referring to system schematic 161412 in
Appendix F, remove wires #18 and #33 from
the lower switch and wires #19 and #33 from
the upper switch.
4. Using an ohmmeter, check for continuity
across the C, common, and NC, normally
closed, terminals of both switches.
5. Replace the switches if either or both show
no continuity
6. If the switches show continuity, disconnect
the 15-pin connector from the control panel.
7. Using an ohmmeter, check wires #18, #19
and #33 back to the 15-pin connector for
continuity.
8. Check for loose connectors on the switch
end of wires #18, #19 and #33.]
9. Check the pins of the 15-pin connector for
proper insertion or wear.
10. If the connectors, pins, and continuity are
okay, restore wires #19 and #33 to the lower
switch and wires #18 and #33 to the upper
temperature switch.
11. Restore the 15-pin connector to the control
panel.
12. Reapply electrical power to the unit.
13. If the over temperature fault does not clear
consult your local AERCO representative or
contact aqualified service technician.
7.4.3 BTU TRANSMITTER PUMP
1. Disconnect electric power to the unit.
2. Referring to system schematic 161412 in
Appendix F, locate wires #10, #30, and #31.
3. Remove the wire nuts from wires #10 and
#31 and connect an AC voltmeter across
wires #10 and #31.
4. Restore electric power to the unit.
5. If there is 120 VAC across wires #10 and
#31, and the pump is not runing, replace the
pump.
6. If 120 VAC is not present across wires #10
and #31, disconnect electric power to the
unit.
7. Disconnect the 9-pin connector from the
control panel and remove the cover from the
unit’s AC wiring box.
8. Check for continuity in wires #10, #30 and
#31. Check for loose connections on wires
#30 and #31 located in the AC wiring box.
9. Check the pin in the 9-pin connector for
proper insertion or signs of wear.
10. If all wire connectors and pins are okay,
replace the control panel.
7.4.4. TEMPERATURE SENSORS
1. Close off the shutoff valves on the water inlet
and outlet lines of the unit. Close off any
recirculation lines to the unit.
2. Drain the unit while venting the shell, through
the relief valve, until a water level fault light
is observed.
3. Drain slightly more, then close the drain
valve.
4. Close off the three ball valves on the BTU
transmitter assembly.
5. Disconnect and remove the BTU transmitter
sensor.
6. Remove the unit cap. Disconnect and
remove the header sensor.
7. Allow the sensors to cool to ambient
temperature.
8. Referring to the Temperature Sensor Chart
in Appendix C of this manual, measure the
resistance of the probe and determine the
corresponding temperature from the chart.
9. Compare the reading with the ambient room
temperature. If there is a significant
discrepancy, greater than 10
o
F, replace the
erroneous sensor.