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3 Troubleshooting
33
Service Manual
Label all wires prior to disconnection
when servicing controls. Wiring
errors can cause improper and
dangerous operation. Always
disconnect power to the boiler before
servicing. Failure to comply could
result in severe personal injury, death,
or substantial property damage.
Never jumper (bypass) any device
except for momentary testing as
outlined in the Troubleshooting
chart. Severe personal injury, death,
or substantial property damage can
result.
Before troubleshooting:
1. Have the following items:
a. Voltmeter that can check 120 VAC, 24 VAC, and
12 VDC.
b. Continuity checker.
c. Contact thermometer.
2. Check for 120 VAC (minimum 102 VAC to maximum
132 VAC) to boiler.
3. Make sure thermostat is calling for heat and contacts
(including appropriate zone controls) are closed.
Check for 24 VAC between thermostat wire nuts and
ground.
4. Make sure all external limit controls are installed and
operating.
Check the following:
1. Wire connectors to control module are securely
plugged in at the module and originating control.
2. Gas pressures:
• Maximum: 14 inches w.c. (3.5 kPa) (natural and
LP) with no flow (lockup) or with boiler on
• Minimum: 4 inches w.c. (1.0 kPa) (natural),
8 inches w.c. (2.0 kPa) (LP) with gas flowing (verify
during boiler startup)
Check control module fuses
ALWAYS check control module fuses before
replacing control module or any major
components (blower, etc.). If one of these
fuses is blown, it can prevent the control
module or other components from operating.
1. Turn OFF the power to the boiler at the external line
switch.
2. Remove top access cover.
3. Remove the control module cover.
4. Inspect fuses F1, F2, and F3, see FIG 3-1 below.
F3 - .80 AMP FUSE
24V DC POWER SUPPLY
F1 - 5 AMP FUSE
PUMPS
F2 - 3.15 AMP FUSE
BLOWER
Figure 3-1 Control Module Fuses
5. The boiler is shipped with three (3) spare fuses in a plastic bag
attached to the control module cover.
6. If necessary, replace open fuse (F3 is .80 amps, F2 is 3.15 amps
and F1 is 5 amps).
Note: Fuses F1, F2, and F3 are all slow blow fuses.
Do not jumper fuse or replace with any fuse
except as specified. Failure to comply could
result in severe personal injury, death, or
substantial property damage.
7. Install control module cover and top access cover after fuse
inspection.
8. Restore power to the boiler at the external line switch and
verify boiler operation (Section 10 - Start-up in the Knight XL
Installation and Operation Manual) after completing boiler
service.
ƽ WARNING
ƽ WARNING
NOTICE
ƽ WARNING