AERCO KC1000 Heater w/Mod-Box Controller - Manual (Page 46)

TROUBLESHOOTING
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5. If 12 VAC is read on the AC voltmeter,
disconnect power to the unit and ground the
probe to the unit shell.
6. Restore electrical power to the unit. If the
fault does not clear, proceed to section
7.3.3. If the fault clears replace the probe.
7.3.2 WIRING AND CONNECTIONS
1. Disconnect electric power to the unit.
2. Disconnect wire #25 from the water level
probe and unplug the 9-pin connector from
the control box.
3. Referring to system schematic 161412 in the
Appendix, 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. Restore the 9-pin connector to the control
panel.
10. Restore electric power to the unit. If the
water level fault does not clear, see Section
7.3.3.
7.3.3 WATER LEVEL CIRCUIT
1. Remove power from the unit.
2. Open the control panel to expose the wiring
and internal components.
WARNING!
This a 120 VAC system.
A shodk hazard exists.
3. Locate the low water level switch as shown
in Appendix E.
4. Remove wires #96 and #99 from terminals
LLCO and G.
5. Using an ohm meter
, check continuity
between wire #96 in the control box , and
wire # 25 on the unit. Also check continuity
between wire #99 in the control box and the
unit’s shell or frame.
6. If there is no continuity repair as necessary.
If there is continuity, replace the low water
level circuit.
7.4 HIGH WATER TEMPERATURE
A HIGH WATER TEMPERATURE fault indicates
when the temperature of the discharge water
has exceeded the setpoint of the over
temperature switches.
First try to clear the fault message from the
Annunciator and start the unit. If the unit fires but
continues to display a HIGH WATER TEMP
message, replace the Annunciator. If the fault
message will not clear and the unit does not fire
check the following.
7.4.1 Determining the Cause
7.4.2 Over Temperature Limit Switches
7.4.3 BTU Transmitter Pump
7.4.4 Temperature Sensors
Recommended Troubleshooting Equipment
Digital Voltmeter
Digital Ohmmeter
7.4.1 DETERMINING THE CAUSE
Remove the unit cap to expose the over
temperature limit switches. Check the setpoint of
the unit and the setpoint of the lower over
temperature switch. The lower over temperature
switch must be set a minimum of 20
o
F higher
than the setpoint of the unit. Make adjustments if
necessary.
1. If the over temperature switch was correctly
set, 20
°
F above the unit setpoint, check that
the feedback is set to ON in the temperature
controller.
2. If the feedback was on, check that the 3 ball
valves on the BTU Transmitter are open.
3. Check that the BTU transmitter is running. If
the pump is not running, proceed to section
7.4.3.
4. If all the above are okay but the High Water
Temp fault persists, recalibrate the unit for
temperature control as per Section 4.7.
5. If the unit cannot be temperature calibrated,
The BTU transmitter must be checked for
scale or blockage as per Maintenance
Section 6.7.
6. If the BTU transmitter has no blockage or
scale, check the temperature sensor probes
as per Section 7.4.4.