Troubleshooting, Check control module fuses

Service Manual

3Troubleshooting

WARNING

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.

Check control module fuses

	NOTICE	ALWAYS check control module fuses before
	NOTICE	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.

WARNING 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.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.

Figure 3-1Control Module Fuses

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.

F3 - .80 AMP FUSE

24V DC POWER SUPPLY

F1 - 5 AMP FUSE

PUMPS

F2 - 3.15 AMP FUSE

BLOWER

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)

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.

WARNING 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.