Aerco KC Series Installation, Operation & Maintenance Instructions Manual page 53

7. Referring to system schematic 161412 in
Appendix F, locate wire #17 and #24 and
check both for continuity.
8. Check the switch end of wires #17 and #24
for loose connections.
9. Check the pins on the 15-pin connector for
proper pin insertion or wear.
10. If continuity, the connector, and pins are
okay, reconnect wires #17 and #24 to the
blower proof switch.
11. Reconnect the 15-pin connector to the
control panel.
12. Restore electrical power to the unit and start
the unit.
13. If the blower proof fault persists, replace the
Combustion Control
7.6.5 SOLID STATE RELAY
1. Open the control box and locate the solid
state relay.
2. Locate wire 81 on terminal 6 of the relay.
Measure the AC voltage on terminal 6 when
the unit is attempting to start. There should
be 120 VAC on terminal 6 at this point
3. If there is 120 VAC on terminal 6 and the
blower still does not start, replace the solid
state relay.
4. If 120 VAC is not measured, replace the
combustion safeguard chassis.
7.7 SYSTEM FAULT
A system fault indicates when the unit faults
during the starting sequence, but prior to ignition.
An internal 30-second fault timer starts timing
when the unit start sequence is initiated. If
ignition is not reached within the specified time,
the Annunciator displays the message SYSTEM
FAULT LOW AIR PRESSURE or PURGE
INTERLOCKS depending on the cause. A
system fault usually occurs when the system
does not acknowledge either the safety shutoff
valve proof of closure switch, the blower proof
switch, or the air/fuel valve open switch.
7.7.1 Determining the cause.
7.7.2 Blower
7.7.3 Combustion Air Supply and Blower
Proof Switch
7.7.4 Purge Interlocks
7.7.5 SSOV Proof of Closure Switch
TROUBLESHOOTING
7.7.6 Air/Fuel Valve Open Proving
Switch
7.7.7 Air Fuel Valve not Rotating
Recommended Troubleshooting
Equipment
AC Voltmeter
Ohmmeter
7.7.1 DETERMINING THE
1. Clear the Annunciator and restart the unit.
2. If the unit does not fire
SYSTEM FAULT LOW AIR PRESSURE is
,
displayed proceed to section 7.7.2.
3. If the unit does not fire a and the message
SYSTEM FAULT PURGE INTERLOCKS is
displayed proceed to section 7.7.4.
4. If the unit does not fire and the message
SYS FLT is displayed on the temperature
controller but the Annunciator does not
display a fault proceed to section 7.7.8.
7.7.2. BLOWER
1. Disconnect power to the unit
2. Remove the cover plate from the AC wiring
box
3. Locate wire #13 and the blower hot lead wire
inside the AC wiring box. These will be the
only two wires connected by a wire nut.
4. Remove the wire nut and separate wire #13
from the blower hot lead wire.
5. Connect an AC voltmeter between wire #18
and the unit frame.
6. Restore electrical power to the unit.
7. Restart the unit.
8. The AC voltmeter should display 120 VAC.
9. If 120 VAC is not displayed, replace the
control panel.
10. If 120 VAC is displayed, check the capacitor
using an analog ohm meter or substitute the
capacitor.
11. If the capacitor checks okay or is substituted
and blower still does not start, replace the
blower.
48
CAUSE
,
and the message