3
Troubleshooting
28
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 F2, F3, F4, and F5, see FIG 3-1 below.
F4 - 3.15 AMP FUSE
GAS VALVE
F3 - 1.25 AMP FUSE
MAIN BOARD
F5 - 5 AMP FUSE
PUMPS
F2 - 3.15 AMP FUSE
24V SUPPLY
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 1.25 amps, F2 and F4
are 3.15 amps, and F5 is 5 amps).
Note:
Fuses F2 - F5 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 Boiler Installation and Operation Manual) after
completing boiler service.
WARNING
WARNING
NOTICE
WARNING
Summary of Contents for KNIGHT 399 - 800
Page 42: ...4 Notes 42 Service Manual...
Page 43: ...4 Notes Service Manual 43...
