Troubleshooting; Before Troubleshooting; Check Control Module Fuses - Lochinvar 50 Service Manual

3

Troubleshooting

Label all wires prior to disconnection
WARNING
when servicing controls. Wiring errors
can cause improper and dangerous
operation. Always disconnect power to
the boiler before servicing.
comply could result in severe personal
injury, death, or substantial property
damage.
Never jumper (bypass) any device except
WARNING
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. (natural and LP) with no flow
(lockup) or with boiler on
• Minimum: 4 inches w.c. (natural), 8 inches w.c. (LP)
with gas flowing (verify during boiler startup)
28

Check control module fuses

NOTICE
Failure to
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 5 below.
Figure 3-1 Control Module Fuses
F4 - 3.15 AMP FUSE
BLOWER
F5 - 5 AMP FUSE
PUMPS
F2 - 3.15 AMP FUSE
24V SUPPLY
5. The boiler is shipped with three (3) spare fuses in a plastic
bag provided with the unit.
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.
WARNING
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.
Service Manual
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.
F3 - 1.25 AMP FUSE
MAIN BOARD
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.