Aerco KC Series Installation, Operation & Maintenance Instructions Manual page 52

7.6 LOCKOUT RUN AIR FLOW
A LOCKOUT RUN AIR FLOW indicates that the
air pressure while running is too low for
operation. Oscillations or rumbling of the unit is
also a common cause of Air Pressure faults.
7.6.1 Determining the Cause of the Fault
7.6.2 Oscillations
7.6.3 Blower
7.6.4 Blower Proof Switch
7.6.5 Solid State Relay
Recommended Troubleshooting Equipment
AC Voltmeter
Ohmmeter
7.6.1 DETERMINING THE CAUSE OF
THE FAULT
1. Clear the Annunciator and restart the unit.
2. If the unit does not fault after proving flame,
proceed to Section 7.6.2.
3. If the blower does not start
Section 7.6.3.
4. If the blower starts but the Annunciator
displays LOW AIR FLOW, proceed to
Section 7.6.4.
5. If the unit has sealed combustion air ducted
in right up to the blower, check the ducting
for blockage.
6. If combustion air is ducted into the room or
brought in through a louver, ensure that the
sizing is adequate and that the louvers are
open while the unit is firing.
7.6.2 OSCILLATIONS
Oscillations, also known as rumbling, typically
occur when the air/fuel mixture is too lean. This
causes the flame to burn at various distances
from the burner at a rapid pace. Oscillations
create pressure waves that can trip the air
pressure switch shutting the unit down on an air
pressure fault.
1. Start the unit in manual mode. Be sure to
have sufficient water flow through the unit to
avoid over temping.
2. Slowly increase the firing rate percentage
while listening to the unit.
,
proceed to
47
TROUBLESHOOTING
3. If a rumbling sound is heard when
approaching firing rates above 75%,
combustion calibrate the unit as per section
4 of this manual.
7.6.3 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. They 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 #13
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, proceed to
section 7.6.5.
10. If 120 VAC is displayed, check the blower
capacitor using an analog ohmmeter or
substitute the capacitor.
11. If the capacitor is okay or has been
substituted and the blower still does not
start, replace the blower.
7.6.4 BLOWER PROOF SWITCH
1. Remove wires #17 and #24 from the blower
proof switch
2. Connect an ohmmeter across the blower
proof switch and restart the unit.
3. The blower proof switch should show
continuity with the blower running.
4. If the blower proof switch does not show
continuity, remove the switch and check for
signs of blockage. Remove any debris and
reinstall the switch. Retest as per Steps 2
through 3.
5. If the blower proof switch shows continuity,
disconnect electrical power to the unit.
6. Disconnect the 15-pin connector from the
control panel.